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Commit Graph

637 Commits

Author SHA1 Message Date
Paolo Bonzini
269a2c3663 Documentation: kvm: remove KVM_CAP_MIPS_TE
Trap and emulate virtualization is not available anymore for MIPS.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2025-04-04 06:32:17 -04:00
Paolo Bonzini
af339282e2 Documentation: kvm: organize capabilities in the right section
Categorize the capabilities correctly.  Section 6 is for enabled vCPU
capabilities; section 7 is for enabled VM capabilities; section 8 is
for informational ones.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2025-04-04 06:32:17 -04:00
Paolo Bonzini
ed7974fd59 Documentation: kvm: fix some definition lists
Ensure that they have a ":" in front of the defined item.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2025-04-04 06:32:17 -04:00
Paolo Bonzini
2f313018de Documentation: kvm: drop "Capability" heading from capabilities
It is redundant, and sometimes wrong.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2025-04-04 06:32:17 -04:00
Paolo Bonzini
26cb30f22f Documentation: kvm: give correct name for KVM_CAP_SPAPR_MULTITCE
The capability is incorrectly called KVM_CAP_PPC_MULTITCE in the documentation.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2025-04-04 06:32:17 -04:00
Paolo Bonzini
f3e555ba45 Documentation: KVM: KVM_GET_SUPPORTED_CPUID now exposes TSC_DEADLINE
TSC_DEADLINE is now advertised unconditionally by KVM_GET_SUPPORTED_CPUID,
since commit 9be4ec35d6 ("KVM: x86: Advertise TSC_DEADLINE_TIMER in
KVM_GET_SUPPORTED_CPUID", 2024-12-18).  Adjust the documentation to
reflect the new behavior.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20250331150550.510320-1-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2025-04-04 06:24:05 -04:00
Paolo Bonzini
0afd104fb3 KVM/arm64 updates for 6.15
- Nested virtualization support for VGICv3, giving the nested
    hypervisor control of the VGIC hardware when running an L2 VM
 
  - Removal of 'late' nested virtualization feature register masking,
    making the supported feature set directly visible to userspace
 
  - Support for emulating FEAT_PMUv3 on Apple silicon, taking advantage
    of an IMPLEMENTATION DEFINED trap that covers all PMUv3 registers
 
  - Paravirtual interface for discovering the set of CPU implementations
    where a VM may run, addressing a longstanding issue of guest CPU
    errata awareness in big-little systems and cross-implementation VM
    migration
 
  - Userspace control of the registers responsible for identifying a
    particular CPU implementation (MIDR_EL1, REVIDR_EL1, AIDR_EL1),
    allowing VMs to be migrated cross-implementation
 
  - pKVM updates, including support for tracking stage-2 page table
    allocations in the protected hypervisor in the 'SecPageTable' stat
 
  - Fixes to vPMU, ensuring that userspace updates to the vPMU after
    KVM_RUN are reflected into the backing perf events
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Merge tag 'kvmarm-6.15' of https://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD

KVM/arm64 updates for 6.15

 - Nested virtualization support for VGICv3, giving the nested
   hypervisor control of the VGIC hardware when running an L2 VM

 - Removal of 'late' nested virtualization feature register masking,
   making the supported feature set directly visible to userspace

 - Support for emulating FEAT_PMUv3 on Apple silicon, taking advantage
   of an IMPLEMENTATION DEFINED trap that covers all PMUv3 registers

 - Paravirtual interface for discovering the set of CPU implementations
   where a VM may run, addressing a longstanding issue of guest CPU
   errata awareness in big-little systems and cross-implementation VM
   migration

 - Userspace control of the registers responsible for identifying a
   particular CPU implementation (MIDR_EL1, REVIDR_EL1, AIDR_EL1),
   allowing VMs to be migrated cross-implementation

 - pKVM updates, including support for tracking stage-2 page table
   allocations in the protected hypervisor in the 'SecPageTable' stat

 - Fixes to vPMU, ensuring that userspace updates to the vPMU after
   KVM_RUN are reflected into the backing perf events
2025-03-20 12:54:12 -04:00
Oliver Upton
4f2774c57a Merge branch 'kvm-arm64/writable-midr' into kvmarm/next
* kvm-arm64/writable-midr:
  : Writable implementation ID registers, courtesy of Sebastian Ott
  :
  : Introduce a new capability that allows userspace to set the
  : ID registers that identify a CPU implementation: MIDR_EL1, REVIDR_EL1,
  : and AIDR_EL1. Also plug a hole in KVM's trap configuration where
  : SMIDR_EL1 was readable at EL1, despite the fact that KVM does not
  : support SME.
  KVM: arm64: Fix documentation for KVM_CAP_ARM_WRITABLE_IMP_ID_REGS
  KVM: arm64: Copy MIDR_EL1 into hyp VM when it is writable
  KVM: arm64: Copy guest CTR_EL0 into hyp VM
  KVM: selftests: arm64: Test writes to MIDR,REVIDR,AIDR
  KVM: arm64: Allow userspace to change the implementation ID registers
  KVM: arm64: Load VPIDR_EL2 with the VM's MIDR_EL1 value
  KVM: arm64: Maintain per-VM copy of implementation ID regs
  KVM: arm64: Set HCR_EL2.TID1 unconditionally

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
2025-03-19 14:54:32 -07:00
Oliver Upton
d300b0168e Merge branch 'kvm-arm64/pv-cpuid' into kvmarm/next
* kvm-arm64/pv-cpuid:
  : Paravirtualized implementation ID, courtesy of Shameer Kolothum
  :
  : Big-little has historically been a pain in the ass to virtualize. The
  : implementation ID (MIDR, REVIDR, AIDR) of a vCPU can change at the whim
  : of vCPU scheduling. This can be particularly annoying when the guest
  : needs to know the underlying implementation to mitigate errata.
  :
  : "Hyperscalers" face a similar scheduling problem, where VMs may freely
  : migrate between hosts in a pool of heterogenous hardware. And yes, our
  : server-class friends are equally riddled with errata too.
  :
  : In absence of an architected solution to this wart on the ecosystem,
  : introduce support for paravirtualizing the implementation exposed
  : to a VM, allowing the VMM to describe the pool of implementations that a
  : VM may be exposed to due to scheduling/migration.
  :
  : Userspace is expected to intercept and handle these hypercalls using the
  : SMCCC filter UAPI, should it choose to do so.
  smccc: kvm_guest: Fix kernel builds for 32 bit arm
  KVM: selftests: Add test for KVM_REG_ARM_VENDOR_HYP_BMAP_2
  smccc/kvm_guest: Enable errata based on implementation CPUs
  arm64: Make  _midr_in_range_list() an exported function
  KVM: arm64: Introduce KVM_REG_ARM_VENDOR_HYP_BMAP_2
  KVM: arm64: Specify hypercall ABI for retrieving target implementations
  arm64: Modify _midr_range() functions to read MIDR/REVIDR internally

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
2025-03-19 14:53:16 -07:00
Oliver Upton
56e3e5c8f7 Merge branch 'kvm-arm64/nv-vgic' into kvmarm/next
* kvm-arm64/nv-vgic:
  : NV VGICv3 support, courtesy of Marc Zyngier
  :
  : Support for emulating the GIC hypervisor controls and managing shadow
  : VGICv3 state for the L1 hypervisor. As part of it, bring in support for
  : taking IRQs to the L1 and UAPI to manage the VGIC maintenance interrupt.
  KVM: arm64: nv: Fail KVM init if asking for NV without GICv3
  KVM: arm64: nv: Allow userland to set VGIC maintenance IRQ
  KVM: arm64: nv: Fold GICv3 host trapping requirements into guest setup
  KVM: arm64: nv: Propagate used_lrs between L1 and L0 contexts
  KVM: arm64: nv: Request vPE doorbell upon nested ERET to L2
  KVM: arm64: nv: Respect virtual HCR_EL2.TWx setting
  KVM: arm64: nv: Add Maintenance Interrupt emulation
  KVM: arm64: nv: Handle L2->L1 transition on interrupt injection
  KVM: arm64: nv: Nested GICv3 emulation
  KVM: arm64: nv: Sanitise ICH_HCR_EL2 accesses
  KVM: arm64: nv: Plumb handling of GICv3 EL2 accesses
  KVM: arm64: nv: Add ICH_*_EL2 registers to vpcu_sysreg
  KVM: arm64: nv: Load timer before the GIC
  arm64: sysreg: Add layout for ICH_MISR_EL2
  arm64: sysreg: Add layout for ICH_VTR_EL2
  arm64: sysreg: Add layout for ICH_HCR_EL2

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
2025-03-19 14:51:43 -07:00
Paolo Bonzini
3ecf162a31 KVM Xen changes for 6.15
- Don't write to the Xen hypercall page on MSR writes that are initiated by
    the host (userspace or KVM) to fix a class of bugs where KVM can write to
    guest memory at unexpected times, e.g. during vCPU creation if userspace has
    set the Xen hypercall MSR index to collide with an MSR that KVM emulates.
 
  - Restrict the Xen hypercall MSR indx to the unofficial synthetic range to
    reduce the set of possible collisions with MSRs that are emulated by KVM
    (collisions can still happen as KVM emulates Hyper-V MSRs, which also reside
    in the synthetic range).
 
  - Clean up and optimize KVM's handling of Xen MSR writes and xen_hvm_config.
 
  - Update Xen TSC leaves during CPUID emulation instead of modifying the CPUID
    entries when updating PV clocks, as there is no guarantee PV clocks will be
    updated between TSC frequency changes and CPUID emulation, and guest reads
    of Xen TSC should be rare, i.e. are not a hot path.
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Merge tag 'kvm-x86-xen-6.15' of https://github.com/kvm-x86/linux into HEAD

KVM Xen changes for 6.15

 - Don't write to the Xen hypercall page on MSR writes that are initiated by
   the host (userspace or KVM) to fix a class of bugs where KVM can write to
   guest memory at unexpected times, e.g. during vCPU creation if userspace has
   set the Xen hypercall MSR index to collide with an MSR that KVM emulates.

 - Restrict the Xen hypercall MSR indx to the unofficial synthetic range to
   reduce the set of possible collisions with MSRs that are emulated by KVM
   (collisions can still happen as KVM emulates Hyper-V MSRs, which also reside
   in the synthetic range).

 - Clean up and optimize KVM's handling of Xen MSR writes and xen_hvm_config.

 - Update Xen TSC leaves during CPUID emulation instead of modifying the CPUID
   entries when updating PV clocks, as there is no guarantee PV clocks will be
   updated between TSC frequency changes and CPUID emulation, and guest reads
   of Xen TSC should be rare, i.e. are not a hot path.
2025-03-19 09:14:59 -04:00
Oliver Upton
5980a69370 KVM: arm64: Fix documentation for KVM_CAP_ARM_WRITABLE_IMP_ID_REGS
The capability actually fails with EINVAL if vCPUs have already been
created.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20250305230825.484091-4-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
2025-03-05 16:56:58 -08:00
Andre Przywara
faf7714a47 KVM: arm64: nv: Allow userland to set VGIC maintenance IRQ
The VGIC maintenance IRQ signals various conditions about the LRs, when
the GIC's virtualization extension is used.
So far we didn't need it, but nested virtualization needs to know about
this interrupt, so add a userland interface to setup the IRQ number.
The architecture mandates that it must be a PPI, on top of that this code
only exports a per-device option, so the PPI is the same on all VCPUs.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
[added some bits of documentation]
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20250225172930.1850838-16-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
2025-03-03 14:57:10 -08:00
Shameer Kolothum
c0000e58c7 KVM: arm64: Introduce KVM_REG_ARM_VENDOR_HYP_BMAP_2
The vendor_hyp_bmap bitmap holds the information about the Vendor Hyp
services available to the user space and can be get/set using
{G, S}ET_ONE_REG interfaces. This is done using the pseudo-firmware
bitmap register KVM_REG_ARM_VENDOR_HYP_BMAP.

At present, this bitmap is a 64 bit one and since the function numbers
for newly added DISCOVER_IPML_* hypercalls are 64-65, introduce
another pseudo-firmware bitmap register KVM_REG_ARM_VENDOR_HYP_BMAP_2.

Reviewed-by: Sebastian Ott <sebott@redhat.com>
Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Link: https://lore.kernel.org/r/20250221140229.12588-4-shameerali.kolothum.thodi@huawei.com
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
2025-02-26 13:30:36 -08:00
Shameer Kolothum
57e5cc9b8a KVM: arm64: Specify hypercall ABI for retrieving target implementations
If the Guest requires migration to multiple targets, these hypercalls
will provide a way to retrieve the target CPU implementations from
the user space VMM.

Subsequent patch will use this to enable the associated errata.

Suggested-by: Oliver Upton <oliver.upton@linux.dev>
Suggested-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Sebastian Ott <sebott@redhat.com>
Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Link: https://lore.kernel.org/r/20250221140229.12588-3-shameerali.kolothum.thodi@huawei.com
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
2025-02-26 13:30:18 -08:00
Oliver Upton
d766d87cf4 KVM: arm64: Document ordering requirements for irqbypass
One of the not-so-obvious requirements for restoring a VM is ensuring
that the vITS has been restored _before_ creating any irqbypass mappings.
This is because KVM needs to get the guest translation for MSIs to
correctly assemble the vLPI mapping getting installed in the physical
ITS.

Document the restore ordering requirements necessary for GICv4 vLPI
injection to work.

Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20250226183124.82094-5-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
2025-02-26 13:22:49 -08:00
Sebastian Ott
3adaee7830 KVM: arm64: Allow userspace to change the implementation ID registers
KVM's treatment of the ID registers that describe the implementation
(MIDR, REVIDR, and AIDR) is interesting, to say the least. On the
userspace-facing end of it, KVM presents the values of the boot CPU on
all vCPUs and treats them as invariant. On the guest side of things KVM
presents the hardware values of the local CPU, which can change during
CPU migration in a big-little system.

While one may call this fragile, there is at least some degree of
predictability around it. For example, if a VMM wanted to present
big-little to a guest, it could affine vCPUs accordingly to the correct
clusters.

All of this makes a giant mess out of adding support for making these
implementation ID registers writable. Avoid breaking the rather subtle
ABI around the old way of doing things by requiring opt-in from
userspace to make the registers writable.

When the cap is enabled, allow userspace to set MIDR, REVIDR, and AIDR
to any non-reserved value and present those values consistently across
all vCPUs.

Signed-off-by: Sebastian Ott <sebott@redhat.com>
[oliver: changelog, capability]
Link: https://lore.kernel.org/r/20250225005401.679536-5-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
2025-02-26 01:32:16 -08:00
Sean Christopherson
5c17848134 KVM: x86/xen: Restrict hypercall MSR to unofficial synthetic range
Reject userspace attempts to set the Xen hypercall page MSR to an index
outside of the "standard" virtualization range [0x40000000, 0x4fffffff],
as KVM is not equipped to handle collisions with real MSRs, e.g. KVM
doesn't update MSR interception, conflicts with VMCS/VMCB fields, special
case writes in KVM, etc.

While the MSR index isn't strictly ABI, i.e. can theoretically float to
any value, in practice no known VMM sets the MSR index to anything other
than 0x40000000 or 0x40000200.

Cc: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
Link: https://lore.kernel.org/r/20250215011437.1203084-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
2025-02-24 08:59:55 -08:00
James Houghton
61d65f2dc7 KVM: x86/mmu: Don't force atomic update if only the Accessed bit is volatile
Don't force SPTE modifications to be done atomically if the only volatile
bit in the SPTE is the Accessed bit.  KVM and the primary MMU tolerate
stale aging state, and the probability of an Accessed bit A/D assist being
clobbered *and* affecting again is likely far lower than the probability
of consuming stale information due to not flushing TLBs when aging.

Rename spte_has_volatile_bits() to spte_needs_atomic_update() to better
capture the nature of the helper.

Opportunstically do s/write/update on the TDP MMU wrapper, as it's not
simply the "write" that needs to be done atomically, it's the entire
update, i.e. the entire read-modify-write operation needs to be done
atomically so that KVM has an accurate view of the old SPTE.

Leave kvm_tdp_mmu_write_spte_atomic() as is.  While the name is imperfect,
it pairs with kvm_tdp_mmu_write_spte(), which in turn pairs with
kvm_tdp_mmu_read_spte().  And renaming all of those isn't obviously a net
positive, and would require significant churn.

Signed-off-by: James Houghton <jthoughton@google.com>
Link: https://lore.kernel.org/r/20250204004038.1680123-6-jthoughton@google.com
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
2025-02-14 07:16:45 -08:00
Claudio Imbrenda
413c98f24c KVM: s390: fake memslot for ucontrol VMs
Create a fake memslot for ucontrol VMs. The fake memslot identity-maps
userspace.

Now memslots will always be present, and ucontrol is not a special case
anymore.

Suggested-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Link: https://lore.kernel.org/r/20250123144627.312456-4-imbrenda@linux.ibm.com
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20250123144627.312456-4-imbrenda@linux.ibm.com>
2025-01-31 12:03:52 +01:00
Linus Torvalds
e2ee2e9b15 KVM/arm64 updates for 6.14
* New features:
 
   - Support for non-protected guest in protected mode, achieving near
     feature parity with the non-protected mode
 
   - Support for the EL2 timers as part of the ongoing NV support
 
   - Allow control of hardware tracing for nVHE/hVHE
 
 * Improvements, fixes and cleanups:
 
   - Massive cleanup of the debug infrastructure, making it a bit less
     awkward and definitely easier to maintain. This should pave the
     way for further optimisations
 
   - Complete rewrite of pKVM's fixed-feature infrastructure, aligning
     it with the rest of KVM and making the code easier to follow
 
   - Large simplification of pKVM's memory protection infrastructure
 
   - Better handling of RES0/RES1 fields for memory-backed system
     registers
 
   - Add a workaround for Qualcomm's Snapdragon X CPUs, which suffer
     from a pretty nasty timer bug
 
   - Small collection of cleanups and low-impact fixes
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Merge tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

Pull KVM/arm64 updates from Will Deacon:
 "New features:

   - Support for non-protected guest in protected mode, achieving near
     feature parity with the non-protected mode

   - Support for the EL2 timers as part of the ongoing NV support

   - Allow control of hardware tracing for nVHE/hVHE

  Improvements, fixes and cleanups:

   - Massive cleanup of the debug infrastructure, making it a bit less
     awkward and definitely easier to maintain. This should pave the way
     for further optimisations

   - Complete rewrite of pKVM's fixed-feature infrastructure, aligning
     it with the rest of KVM and making the code easier to follow

   - Large simplification of pKVM's memory protection infrastructure

   - Better handling of RES0/RES1 fields for memory-backed system
     registers

   - Add a workaround for Qualcomm's Snapdragon X CPUs, which suffer
     from a pretty nasty timer bug

   - Small collection of cleanups and low-impact fixes"

* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (87 commits)
  arm64/sysreg: Get rid of TRFCR_ELx SysregFields
  KVM: arm64: nv: Fix doc header layout for timers
  KVM: arm64: nv: Apply RESx settings to sysreg reset values
  KVM: arm64: nv: Always evaluate HCR_EL2 using sanitising accessors
  KVM: arm64: Fix selftests after sysreg field name update
  coresight: Pass guest TRFCR value to KVM
  KVM: arm64: Support trace filtering for guests
  KVM: arm64: coresight: Give TRBE enabled state to KVM
  coresight: trbe: Remove redundant disable call
  arm64/sysreg/tools: Move TRFCR definitions to sysreg
  tools: arm64: Update sysreg.h header files
  KVM: arm64: Drop pkvm_mem_transition for host/hyp donations
  KVM: arm64: Drop pkvm_mem_transition for host/hyp sharing
  KVM: arm64: Drop pkvm_mem_transition for FF-A
  KVM: arm64: Explicitly handle BRBE traps as UNDEFINED
  KVM: arm64: vgic: Use str_enabled_disabled() in vgic_v3_probe()
  arm64: kvm: Introduce nvhe stack size constants
  KVM: arm64: Fix nVHE stacktrace VA bits mask
  KVM: arm64: Fix FEAT_MTE in pKVM
  Documentation: Update the behaviour of "kvm-arm.mode"
  ...
2025-01-28 09:01:36 -08:00
Linus Torvalds
0f8e26b38d Loongarch:
* Clear LLBCTL if secondary mmu mapping changes.
 
 * Add hypercall service support for usermode VMM.
 
 x86:
 
 * Add a comment to kvm_mmu_do_page_fault() to explain why KVM performs a
   direct call to kvm_tdp_page_fault() when RETPOLINE is enabled.
 
 * Ensure that all SEV code is compiled out when disabled in Kconfig, even
   if building with less brilliant compilers.
 
 * Remove a redundant TLB flush on AMD processors when guest CR4.PGE changes.
 
 * Use str_enabled_disabled() to replace open coded strings.
 
 * Drop kvm_x86_ops.hwapic_irr_update() as KVM updates hardware's APICv cache
   prior to every VM-Enter.
 
 * Overhaul KVM's CPUID feature infrastructure to track all vCPU capabilities
   instead of just those where KVM needs to manage state and/or explicitly
   enable the feature in hardware.  Along the way, refactor the code to make
   it easier to add features, and to make it more self-documenting how KVM
   is handling each feature.
 
 * Rework KVM's handling of VM-Exits during event vectoring; this plugs holes
   where KVM unintentionally puts the vCPU into infinite loops in some scenarios
   (e.g. if emulation is triggered by the exit), and brings parity between VMX
   and SVM.
 
 * Add pending request and interrupt injection information to the kvm_exit and
   kvm_entry tracepoints respectively.
 
 * Fix a relatively benign flaw where KVM would end up redoing RDPKRU when
   loading guest/host PKRU, due to a refactoring of the kernel helpers that
   didn't account for KVM's pre-checking of the need to do WRPKRU.
 
 * Make the completion of hypercalls go through the complete_hypercall
   function pointer argument, no matter if the hypercall exits to
   userspace or not.  Previously, the code assumed that KVM_HC_MAP_GPA_RANGE
   specifically went to userspace, and all the others did not; the new code
   need not special case KVM_HC_MAP_GPA_RANGE and in fact does not care at
   all whether there was an exit to userspace or not.
 
 * As part of enabling TDX virtual machines, support support separation of
   private/shared EPT into separate roots.  When TDX will be enabled, operations
   on private pages will need to go through the privileged TDX Module via SEAMCALLs;
   as a result, they are limited and relatively slow compared to reading a PTE.
   The patches included in 6.14 allow KVM to keep a mirror of the private EPT in
   host memory, and define entries in kvm_x86_ops to operate on external page
   tables such as the TDX private EPT.
 
 * The recently introduced conversion of the NX-page reclamation kthread to
   vhost_task moved the task under the main process.  The task is created as
   soon as KVM_CREATE_VM was invoked and this, of course, broke userspace that
   didn't expect to see any child task of the VM process until it started
   creating its own userspace threads.  In particular crosvm refuses to fork()
   if procfs shows any child task, so unbreak it by creating the task lazily.
   This is arguably a userspace bug, as there can be other kinds of legitimate
   worker tasks and they wouldn't impede fork(); but it's not like userspace
   has a way to distinguish kernel worker tasks right now.  Should they show
   as "Kthread: 1" in proc/.../status?
 
 x86 - Intel:
 
 * Fix a bug where KVM updates hardware's APICv cache of the highest ISR bit
   while L2 is active, while ultimately results in a hardware-accelerated L1
   EOI effectively being lost.
 
 * Honor event priority when emulating Posted Interrupt delivery during nested
   VM-Enter by queueing KVM_REQ_EVENT instead of immediately handling the
   interrupt.
 
 * Rework KVM's processing of the Page-Modification Logging buffer to reap
   entries in the same order they were created, i.e. to mark gfns dirty in the
   same order that hardware marked the page/PTE dirty.
 
 * Misc cleanups.
 
 Generic:
 
 * Cleanup and harden kvm_set_memory_region(); add proper lockdep assertions when
   setting memory regions and add a dedicated API for setting KVM-internal
   memory regions.  The API can then explicitly disallow all flags for
   KVM-internal memory regions.
 
 * Explicitly verify the target vCPU is online in kvm_get_vcpu() to fix a bug
   where KVM would return a pointer to a vCPU prior to it being fully online,
   and give kvm_for_each_vcpu() similar treatment to fix a similar flaw.
 
 * Wait for a vCPU to come online prior to executing a vCPU ioctl, to fix a
   bug where userspace could coerce KVM into handling the ioctl on a vCPU that
   isn't yet onlined.
 
 * Gracefully handle xarray insertion failures; even though such failures are
   impossible in practice after xa_reserve(), reserving an entry is always followed
   by xa_store() which does not know (or differentiate) whether there was an
   xa_reserve() before or not.
 
 RISC-V:
 
 * Zabha, Svvptc, and Ziccrse extension support for guests.  None of them
   require anything in KVM except for detecting them and marking them
   as supported; Zabha adds byte and halfword atomic operations, while the
   others are markers for specific operation of the TLB and of LL/SC
   instructions respectively.
 
 * Virtualize SBI system suspend extension for Guest/VM
 
 * Support firmware counters which can be used by the guests to collect
   statistics about traps that occur in the host.
 
 Selftests:
 
 * Rework vcpu_get_reg() to return a value instead of using an out-param, and
   update all affected arch code accordingly.
 
 * Convert the max_guest_memory_test into a more generic mmu_stress_test.
   The basic gist of the "conversion" is to have the test do mprotect() on
   guest memory while vCPUs are accessing said memory, e.g. to verify KVM
   and mmu_notifiers are working as intended.
 
 * Play nice with treewrite builds of unsupported architectures, e.g. arm
   (32-bit), as KVM selftests' Makefile doesn't do anything to ensure the
   target architecture is actually one KVM selftests supports.
 
 * Use the kernel's $(ARCH) definition instead of the target triple for arch
   specific directories, e.g. arm64 instead of aarch64, mainly so as not to
   be different from the rest of the kernel.
 
 * Ensure that format strings for logging statements are checked by the
   compiler even when the logging statement itself is disabled.
 
 * Attempt to whack the last LLC references/misses mole in the Intel PMU
   counters test by adding a data load and doing CLFLUSH{OPT} on the data
   instead of the code being executed.  It seems that modern Intel CPUs
   have learned new code prefetching tricks that bypass the PMU counters.
 
 * Fix a flaw in the Intel PMU counters test where it asserts that events
   are counting correctly without actually knowing what the events count
   given the underlying hardware; this can happen if Intel reuses a
   formerly microarchitecture-specific event encoding as an architectural
   event, as was the case for Top-Down Slots.
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull kvm updates from Paolo Bonzini:
 "Loongarch:

   - Clear LLBCTL if secondary mmu mapping changes

   - Add hypercall service support for usermode VMM

  x86:

   - Add a comment to kvm_mmu_do_page_fault() to explain why KVM
     performs a direct call to kvm_tdp_page_fault() when RETPOLINE is
     enabled

   - Ensure that all SEV code is compiled out when disabled in Kconfig,
     even if building with less brilliant compilers

   - Remove a redundant TLB flush on AMD processors when guest CR4.PGE
     changes

   - Use str_enabled_disabled() to replace open coded strings

   - Drop kvm_x86_ops.hwapic_irr_update() as KVM updates hardware's
     APICv cache prior to every VM-Enter

   - Overhaul KVM's CPUID feature infrastructure to track all vCPU
     capabilities instead of just those where KVM needs to manage state
     and/or explicitly enable the feature in hardware. Along the way,
     refactor the code to make it easier to add features, and to make it
     more self-documenting how KVM is handling each feature

   - Rework KVM's handling of VM-Exits during event vectoring; this
     plugs holes where KVM unintentionally puts the vCPU into infinite
     loops in some scenarios (e.g. if emulation is triggered by the
     exit), and brings parity between VMX and SVM

   - Add pending request and interrupt injection information to the
     kvm_exit and kvm_entry tracepoints respectively

   - Fix a relatively benign flaw where KVM would end up redoing RDPKRU
     when loading guest/host PKRU, due to a refactoring of the kernel
     helpers that didn't account for KVM's pre-checking of the need to
     do WRPKRU

   - Make the completion of hypercalls go through the complete_hypercall
     function pointer argument, no matter if the hypercall exits to
     userspace or not.

     Previously, the code assumed that KVM_HC_MAP_GPA_RANGE specifically
     went to userspace, and all the others did not; the new code need
     not special case KVM_HC_MAP_GPA_RANGE and in fact does not care at
     all whether there was an exit to userspace or not

   - As part of enabling TDX virtual machines, support support
     separation of private/shared EPT into separate roots.

     When TDX will be enabled, operations on private pages will need to
     go through the privileged TDX Module via SEAMCALLs; as a result,
     they are limited and relatively slow compared to reading a PTE.

     The patches included in 6.14 allow KVM to keep a mirror of the
     private EPT in host memory, and define entries in kvm_x86_ops to
     operate on external page tables such as the TDX private EPT

   - The recently introduced conversion of the NX-page reclamation
     kthread to vhost_task moved the task under the main process. The
     task is created as soon as KVM_CREATE_VM was invoked and this, of
     course, broke userspace that didn't expect to see any child task of
     the VM process until it started creating its own userspace threads.

     In particular crosvm refuses to fork() if procfs shows any child
     task, so unbreak it by creating the task lazily. This is arguably a
     userspace bug, as there can be other kinds of legitimate worker
     tasks and they wouldn't impede fork(); but it's not like userspace
     has a way to distinguish kernel worker tasks right now. Should they
     show as "Kthread: 1" in proc/.../status?

  x86 - Intel:

   - Fix a bug where KVM updates hardware's APICv cache of the highest
     ISR bit while L2 is active, while ultimately results in a
     hardware-accelerated L1 EOI effectively being lost

   - Honor event priority when emulating Posted Interrupt delivery
     during nested VM-Enter by queueing KVM_REQ_EVENT instead of
     immediately handling the interrupt

   - Rework KVM's processing of the Page-Modification Logging buffer to
     reap entries in the same order they were created, i.e. to mark gfns
     dirty in the same order that hardware marked the page/PTE dirty

   - Misc cleanups

  Generic:

   - Cleanup and harden kvm_set_memory_region(); add proper lockdep
     assertions when setting memory regions and add a dedicated API for
     setting KVM-internal memory regions. The API can then explicitly
     disallow all flags for KVM-internal memory regions

   - Explicitly verify the target vCPU is online in kvm_get_vcpu() to
     fix a bug where KVM would return a pointer to a vCPU prior to it
     being fully online, and give kvm_for_each_vcpu() similar treatment
     to fix a similar flaw

   - Wait for a vCPU to come online prior to executing a vCPU ioctl, to
     fix a bug where userspace could coerce KVM into handling the ioctl
     on a vCPU that isn't yet onlined

   - Gracefully handle xarray insertion failures; even though such
     failures are impossible in practice after xa_reserve(), reserving
     an entry is always followed by xa_store() which does not know (or
     differentiate) whether there was an xa_reserve() before or not

  RISC-V:

   - Zabha, Svvptc, and Ziccrse extension support for guests. None of
     them require anything in KVM except for detecting them and marking
     them as supported; Zabha adds byte and halfword atomic operations,
     while the others are markers for specific operation of the TLB and
     of LL/SC instructions respectively

   - Virtualize SBI system suspend extension for Guest/VM

   - Support firmware counters which can be used by the guests to
     collect statistics about traps that occur in the host

  Selftests:

   - Rework vcpu_get_reg() to return a value instead of using an
     out-param, and update all affected arch code accordingly

   - Convert the max_guest_memory_test into a more generic
     mmu_stress_test. The basic gist of the "conversion" is to have the
     test do mprotect() on guest memory while vCPUs are accessing said
     memory, e.g. to verify KVM and mmu_notifiers are working as
     intended

   - Play nice with treewrite builds of unsupported architectures, e.g.
     arm (32-bit), as KVM selftests' Makefile doesn't do anything to
     ensure the target architecture is actually one KVM selftests
     supports

   - Use the kernel's $(ARCH) definition instead of the target triple
     for arch specific directories, e.g. arm64 instead of aarch64,
     mainly so as not to be different from the rest of the kernel

   - Ensure that format strings for logging statements are checked by
     the compiler even when the logging statement itself is disabled

   - Attempt to whack the last LLC references/misses mole in the Intel
     PMU counters test by adding a data load and doing CLFLUSH{OPT} on
     the data instead of the code being executed. It seems that modern
     Intel CPUs have learned new code prefetching tricks that bypass the
     PMU counters

   - Fix a flaw in the Intel PMU counters test where it asserts that
     events are counting correctly without actually knowing what the
     events count given the underlying hardware; this can happen if
     Intel reuses a formerly microarchitecture-specific event encoding
     as an architectural event, as was the case for Top-Down Slots"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (151 commits)
  kvm: defer huge page recovery vhost task to later
  KVM: x86/mmu: Return RET_PF* instead of 1 in kvm_mmu_page_fault()
  KVM: Disallow all flags for KVM-internal memslots
  KVM: x86: Drop double-underscores from __kvm_set_memory_region()
  KVM: Add a dedicated API for setting KVM-internal memslots
  KVM: Assert slots_lock is held when setting memory regions
  KVM: Open code kvm_set_memory_region() into its sole caller (ioctl() API)
  LoongArch: KVM: Add hypercall service support for usermode VMM
  LoongArch: KVM: Clear LLBCTL if secondary mmu mapping is changed
  KVM: SVM: Use str_enabled_disabled() helper in svm_hardware_setup()
  KVM: VMX: read the PML log in the same order as it was written
  KVM: VMX: refactor PML terminology
  KVM: VMX: Fix comment of handle_vmx_instruction()
  KVM: VMX: Reinstate __exit attribute for vmx_exit()
  KVM: SVM: Use str_enabled_disabled() helper in sev_hardware_setup()
  KVM: x86: Avoid double RDPKRU when loading host/guest PKRU
  KVM: x86: Use LVT_TIMER instead of an open coded literal
  RISC-V: KVM: Add new exit statstics for redirected traps
  RISC-V: KVM: Update firmware counters for various events
  RISC-V: KVM: Redirect instruction access fault trap to guest
  ...
2025-01-25 09:55:09 -08:00
Linus Torvalds
382e391365 hyperv-next for v6.14
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Merge tag 'hyperv-next-signed-20250123' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux

Pull hyperv updates from Wei Liu:

 - Introduce a new set of Hyper-V headers in include/hyperv and replace
   the old hyperv-tlfs.h with the new headers (Nuno Das Neves)

 - Fixes for the Hyper-V VTL mode (Roman Kisel)

 - Fixes for cpu mask usage in Hyper-V code (Michael Kelley)

 - Document the guest VM hibernation behaviour (Michael Kelley)

 - Miscellaneous fixes and cleanups (Jacob Pan, John Starks, Naman Jain)

* tag 'hyperv-next-signed-20250123' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux:
  Documentation: hyperv: Add overview of guest VM hibernation
  hyperv: Do not overlap the hvcall IO areas in hv_vtl_apicid_to_vp_id()
  hyperv: Do not overlap the hvcall IO areas in get_vtl()
  hyperv: Enable the hypercall output page for the VTL mode
  hv_balloon: Fallback to generic_online_page() for non-HV hot added mem
  Drivers: hv: vmbus: Log on missing offers if any
  Drivers: hv: vmbus: Wait for boot-time offers during boot and resume
  uio_hv_generic: Add a check for HV_NIC for send, receive buffers setup
  iommu/hyper-v: Don't assume cpu_possible_mask is dense
  Drivers: hv: Don't assume cpu_possible_mask is dense
  x86/hyperv: Don't assume cpu_possible_mask is dense
  hyperv: Remove the now unused hyperv-tlfs.h files
  hyperv: Switch from hyperv-tlfs.h to hyperv/hvhdk.h
  hyperv: Add new Hyper-V headers in include/hyperv
  hyperv: Clean up unnecessary #includes
  hyperv: Move hv_connection_id to hyperv-tlfs.h
2025-01-25 09:22:55 -08:00
Linus Torvalds
d0f93ac2c3 Documentation changes this time around include:
- Quite a bit of Chinese and Spanish translation work.
 
 - Clarifying that Git commit IDs >12chars are OK
 
 - A new nvme-multipath document
 
 - A reorganization of the admin-guide top-level page to make it readable
 
 - Clarification of the role of Acked-by and maintainer discretion on their
   acceptance.
 
 - Some reorganization of debugging-oriented docs.
 
 ...and typo fixes, documentation updates, etc. as usual.
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Merge tag 'docs-6.14' of git://git.lwn.net/linux

Pull Documentation updates from Jonathan Corbet:

 - Quite a bit of Chinese and Spanish translation work

 - Clarifying that Git commit IDs >12chars are OK

 - A new nvme-multipath document

 - A reorganization of the admin-guide top-level page to make it
   readable

 - Clarification of the role of Acked-by and maintainer discretion on
   their acceptance

 - Some reorganization of debugging-oriented docs

... and typo fixes, documentation updates, etc as usual

* tag 'docs-6.14' of git://git.lwn.net/linux: (50 commits)
  Documentation: Fix x86_64 UEFI outdated references to elilo
  Documentation/sysctl: Add timer_migration to kernel.rst
  docs/mm: Physical memory: Remove zone_t
  docs: submitting-patches: clarify that signers may use their discretion on tags
  docs: submitting-patches: clarify difference between Acked-by and Reviewed-by
  docs: submitting-patches: clarify Acked-by and introduce "# Suffix"
  Documentation: bug-hunting.rst: remove odd contact information
  docs/zh_CN: Add sak index Chinese translation
  doc: module: DEFAULT_SYMBOL_NAMESPACE must be defined before #includes
  doc: module: Fix documented type of namespace
  Documentation/kernel-parameters: Fix a reference to vga-softcursor.rst
  docs/zh_CN: Add landlock index Chinese translation
  Documentation: Fix typo localmodonfig -> localmodconfig
  overlayfs.rst: Fix and improve grammar
  docs/zh_CN: Add siphash index Chinese translation
  docs/zh_CN: Add security IMA-templates Chinese translation
  docs/zh_CN: Add security digsig Chinese translation
  Align git commit ID abbreviation guidelines and checks
  docs: process: submitting-patches: split canonical patch format section
  docs/zh_CN: Add security lsm Chinese translation
  ...
2025-01-21 18:00:00 -08:00
Paolo Bonzini
4f7ff70c05 KVM x86 misc changes for 6.14:
- Overhaul KVM's CPUID feature infrastructure to replace "governed" features
    with per-vCPU tracking of the vCPU's capabailities for all features.  Along
    the way, refactor the code to make it easier to add/modify features, and
    add a variety of self-documenting macro types to again simplify adding new
    features and to help readers understand KVM's handling of existing features.
 
  - Rework KVM's handling of VM-Exits during event vectoring to plug holes where
    KVM unintentionally puts the vCPU into infinite loops in some scenarios,
    e.g. if emulation is triggered by the exit, and to bring parity between VMX
    and SVM.
 
  - Add pending request and interrupt injection information to the kvm_exit and
    kvm_entry tracepoints respectively.
 
  - Fix a relatively benign flaw where KVM would end up redoing RDPKRU when
    loading guest/host PKRU due to a refactoring of the kernel helpers that
    didn't account for KVM's pre-checking of the need to do WRPKRU.
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Merge tag 'kvm-x86-misc-6.14' of https://github.com/kvm-x86/linux into HEAD

KVM x86 misc changes for 6.14:

 - Overhaul KVM's CPUID feature infrastructure to track all vCPU capabilities
   instead of just those where KVM needs to manage state and/or explicitly
   enable the feature in hardware.  Along the way, refactor the code to make
   it easier to add features, and to make it more self-documenting how KVM
   is handling each feature.

 - Rework KVM's handling of VM-Exits during event vectoring; this plugs holes
   where KVM unintentionally puts the vCPU into infinite loops in some scenarios
   (e.g. if emulation is triggered by the exit), and brings parity between VMX
   and SVM.

 - Add pending request and interrupt injection information to the kvm_exit and
   kvm_entry tracepoints respectively.

 - Fix a relatively benign flaw where KVM would end up redoing RDPKRU when
   loading guest/host PKRU, due to a refactoring of the kernel helpers that
   didn't account for KVM's pre-checking of the need to do WRPKRU.
2025-01-20 06:49:39 -05:00
Marc Zyngier
544786361d KVM: arm64: nv: Fix doc header layout for timers
Stephen reports that 'make htmldocs' spits out a warning
("Documentation/virt/kvm/devices/vcpu.rst:147: WARNING: Definition
list ends without a blank line; unexpected unindent.").

Fix it by keeping all the timer attributes on a single line.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Marc Zyngier <maz@kernel.org>
2025-01-16 10:27:10 +00:00
Michael Kelley
2e03358be7 Documentation: hyperv: Add overview of guest VM hibernation
Add documentation on how hibernation works in a guest VM on Hyper-V.
Describe how VMBus devices and the VMBus itself are hibernated and
resumed, along with various limitations.

Signed-off-by: Michael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/20250113145645.1320942-1-mhklinux@outlook.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20250113145645.1320942-1-mhklinux@outlook.com>
2025-01-13 19:17:59 +00:00
Christoph Schlameuss
5021fd77d6 KVM: s390: Reject KVM_SET_GSI_ROUTING on ucontrol VMs
Prevent null pointer dereference when processing
KVM_IRQ_ROUTING_S390_ADAPTER routing entries.
The ioctl cannot be processed for ucontrol VMs.

Fixes: f65470661f ("KVM: s390/interrupt: do not pin adapter interrupt pages")
Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Tested-by: Hariharan Mari <hari55@linux.ibm.com>
Reviewed-by: Hariharan Mari <hari55@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Link: https://lore.kernel.org/r/20241216092140.329196-4-schlameuss@linux.ibm.com
Message-ID: <20241216092140.329196-4-schlameuss@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
2025-01-07 16:36:11 +01:00
Christoph Schlameuss
df989238fa KVM: s390: Reject setting flic pfault attributes on ucontrol VMs
Prevent null pointer dereference when processing the
KVM_DEV_FLIC_APF_ENABLE and KVM_DEV_FLIC_APF_DISABLE_WAIT ioctls in the
interrupt controller.

Fixes: 3c038e6be0 ("KVM: async_pf: Async page fault support on s390")
Reported-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Reviewed-by: Hariharan Mari <hari55@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Link: https://lore.kernel.org/r/20241216092140.329196-2-schlameuss@linux.ibm.com
Message-ID: <20241216092140.329196-2-schlameuss@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
2025-01-07 16:36:10 +01:00
Marc Zyngier
affd1c83e0 KVM: arm64: nv: Document EL2 timer API
Acked-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20241217142321.763801-13-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
2025-01-02 19:19:10 +00:00
Sean Christopherson
9be4ec35d6 KVM: x86: Advertise TSC_DEADLINE_TIMER in KVM_GET_SUPPORTED_CPUID
Unconditionally advertise TSC_DEADLINE_TIMER via KVM_GET_SUPPORTED_CPUID,
as KVM always emulates deadline mode, *if* the VM has an in-kernel local
APIC.  The odds of a VMM emulating the local APIC in userspace, not
emulating the TSC deadline timer, _and_ reflecting
KVM_GET_SUPPORTED_CPUID back into KVM_SET_CPUID2, i.e. the risk of
over-advertising and breaking any setups, is extremely low.

KVM has _unconditionally_ advertised X2APIC via CPUID since commit
0d1de2d901 ("KVM: Always report x2apic as supported feature"), and it
is completely impossible for userspace to emulate X2APIC as KVM doesn't
support forwarding the MSR accesses to userspace.  I.e. KVM has relied on
userspace VMMs to not misreport local APIC capabilities for nearly 13
years.

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20241128013424.4096668-38-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
2024-12-18 14:20:01 -08:00
Sean Christopherson
04cd8f8628 KVM: x86: Disallow KVM_CAP_X86_DISABLE_EXITS after vCPU creation
Reject KVM_CAP_X86_DISABLE_EXITS if vCPUs have been created, as disabling
PAUSE/MWAIT/HLT exits after vCPUs have been created is broken and useless,
e.g. except for PAUSE on SVM, the relevant intercepts aren't updated after
vCPU creation.  vCPUs may also end up with an inconsistent configuration
if exits are disabled between creation of multiple vCPUs.

Cc: Hou Wenlong <houwenlong.hwl@antgroup.com>
Link: https://lore.kernel.org/all/9227068821b275ac547eb2ede09ec65d2281fe07.1680179693.git.houwenlong.hwl@antgroup.com
Link: https://lore.kernel.org/all/20230121020738.2973-2-kechenl@nvidia.com
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Link: https://lore.kernel.org/r/20241128013424.4096668-14-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
2024-12-18 14:19:35 -08:00
Gianfranco Trad
311cf7164a Documentation: kvm: fix typo in api.rst
Fix minor typo in api.rst where the word physical was misspelled
as physcial.

Signed-off-by: Gianfranco Trad <gianf.trad@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20241115011831.300705-5-gianf.trad@gmail.com
2024-12-11 09:07:40 -07:00
Linus Torvalds
9f16d5e6f2 The biggest change here is eliminating the awful idea that KVM had, of
essentially guessing which pfns are refcounted pages.  The reason to
 do so was that KVM needs to map both non-refcounted pages (for example
 BARs of VFIO devices) and VM_PFNMAP/VM_MIXMEDMAP VMAs that contain
 refcounted pages.  However, the result was security issues in the past,
 and more recently the inability to map VM_IO and VM_PFNMAP memory
 that _is_ backed by struct page but is not refcounted.  In particular
 this broke virtio-gpu blob resources (which directly map host graphics
 buffers into the guest as "vram" for the virtio-gpu device) with the
 amdgpu driver, because amdgpu allocates non-compound higher order pages
 and the tail pages could not be mapped into KVM.
 
 This requires adjusting all uses of struct page in the per-architecture
 code, to always work on the pfn whenever possible.  The large series that
 did this, from David Stevens and Sean Christopherson, also cleaned up
 substantially the set of functions that provided arch code with the
 pfn for a host virtual addresses.  The previous maze of twisty little
 passages, all different, is replaced by five functions (__gfn_to_page,
 __kvm_faultin_pfn, the non-__ versions of these two, and kvm_prefetch_pages)
 saving almost 200 lines of code.
 
 ARM:
 
 * Support for stage-1 permission indirection (FEAT_S1PIE) and
   permission overlays (FEAT_S1POE), including nested virt + the
   emulated page table walker
 
 * Introduce PSCI SYSTEM_OFF2 support to KVM + client driver. This call
   was introduced in PSCIv1.3 as a mechanism to request hibernation,
   similar to the S4 state in ACPI
 
 * Explicitly trap + hide FEAT_MPAM (QoS controls) from KVM guests. As
   part of it, introduce trivial initialization of the host's MPAM
   context so KVM can use the corresponding traps
 
 * PMU support under nested virtualization, honoring the guest
   hypervisor's trap configuration and event filtering when running a
   nested guest
 
 * Fixes to vgic ITS serialization where stale device/interrupt table
   entries are not zeroed when the mapping is invalidated by the VM
 
 * Avoid emulated MMIO completion if userspace has requested synchronous
   external abort injection
 
 * Various fixes and cleanups affecting pKVM, vCPU initialization, and
   selftests
 
 LoongArch:
 
 * Add iocsr and mmio bus simulation in kernel.
 
 * Add in-kernel interrupt controller emulation.
 
 * Add support for virtualization extensions to the eiointc irqchip.
 
 PPC:
 
 * Drop lingering and utterly obsolete references to PPC970 KVM, which was
   removed 10 years ago.
 
 * Fix incorrect documentation references to non-existing ioctls
 
 RISC-V:
 
 * Accelerate KVM RISC-V when running as a guest
 
 * Perf support to collect KVM guest statistics from host side
 
 s390:
 
 * New selftests: more ucontrol selftests and CPU model sanity checks
 
 * Support for the gen17 CPU model
 
 * List registers supported by KVM_GET/SET_ONE_REG in the documentation
 
 x86:
 
 * Cleanup KVM's handling of Accessed and Dirty bits to dedup code, improve
   documentation, harden against unexpected changes.  Even if the hardware
   A/D tracking is disabled, it is possible to use the hardware-defined A/D
   bits to track if a PFN is Accessed and/or Dirty, and that removes a lot
   of special cases.
 
 * Elide TLB flushes when aging secondary PTEs, as has been done in x86's
   primary MMU for over 10 years.
 
 * Recover huge pages in-place in the TDP MMU when dirty page logging is
   toggled off, instead of zapping them and waiting until the page is
   re-accessed to create a huge mapping.  This reduces vCPU jitter.
 
 * Batch TLB flushes when dirty page logging is toggled off.  This reduces
   the time it takes to disable dirty logging by ~3x.
 
 * Remove the shrinker that was (poorly) attempting to reclaim shadow page
   tables in low-memory situations.
 
 * Clean up and optimize KVM's handling of writes to MSR_IA32_APICBASE.
 
 * Advertise CPUIDs for new instructions in Clearwater Forest
 
 * Quirk KVM's misguided behavior of initialized certain feature MSRs to
   their maximum supported feature set, which can result in KVM creating
   invalid vCPU state.  E.g. initializing PERF_CAPABILITIES to a non-zero
   value results in the vCPU having invalid state if userspace hides PDCM
   from the guest, which in turn can lead to save/restore failures.
 
 * Fix KVM's handling of non-canonical checks for vCPUs that support LA57
   to better follow the "architecture", in quotes because the actual
   behavior is poorly documented.  E.g. most MSR writes and descriptor
   table loads ignore CR4.LA57 and operate purely on whether the CPU
   supports LA57.
 
 * Bypass the register cache when querying CPL from kvm_sched_out(), as
   filling the cache from IRQ context is generally unsafe; harden the
   cache accessors to try to prevent similar issues from occuring in the
   future.  The issue that triggered this change was already fixed in 6.12,
   but was still kinda latent.
 
 * Advertise AMD_IBPB_RET to userspace, and fix a related bug where KVM
   over-advertises SPEC_CTRL when trying to support cross-vendor VMs.
 
 * Minor cleanups
 
 * Switch hugepage recovery thread to use vhost_task.  These kthreads can
   consume significant amounts of CPU time on behalf of a VM or in response
   to how the VM behaves (for example how it accesses its memory); therefore
   KVM tried to place the thread in the VM's cgroups and charge the CPU
   time consumed by that work to the VM's container.  However the kthreads
   did not process SIGSTOP/SIGCONT, and therefore cgroups which had KVM
   instances inside could not complete freezing.  Fix this by replacing the
   kthread with a PF_USER_WORKER thread, via the vhost_task abstraction.
   Another 100+ lines removed, with generally better behavior too like
   having these threads properly parented in the process tree.
 
 * Revert a workaround for an old CPU erratum (Nehalem/Westmere) that didn't
   really work; there was really nothing to work around anyway: the broken
   patch was meant to fix nested virtualization, but the PERF_GLOBAL_CTRL
   MSR is virtualized and therefore unaffected by the erratum.
 
 * Fix 6.12 regression where CONFIG_KVM will be built as a module even
   if asked to be builtin, as long as neither KVM_INTEL nor KVM_AMD is 'y'.
 
 x86 selftests:
 
 * x86 selftests can now use AVX.
 
 Documentation:
 
 * Use rST internal links
 
 * Reorganize the introduction to the API document
 
 Generic:
 
 * Protect vcpu->pid accesses outside of vcpu->mutex with a rwlock instead
   of RCU, so that running a vCPU on a different task doesn't encounter long
   due to having to wait for all CPUs become quiescent.  In general both reads
   and writes are rare, but userspace that supports confidential computing is
   introducing the use of "helper" vCPUs that may jump from one host processor
   to another.  Those will be very happy to trigger a synchronize_rcu(), and
   the effect on performance is quite the disaster.
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull kvm updates from Paolo Bonzini:
 "The biggest change here is eliminating the awful idea that KVM had of
  essentially guessing which pfns are refcounted pages.

  The reason to do so was that KVM needs to map both non-refcounted
  pages (for example BARs of VFIO devices) and VM_PFNMAP/VM_MIXMEDMAP
  VMAs that contain refcounted pages.

  However, the result was security issues in the past, and more recently
  the inability to map VM_IO and VM_PFNMAP memory that _is_ backed by
  struct page but is not refcounted. In particular this broke virtio-gpu
  blob resources (which directly map host graphics buffers into the
  guest as "vram" for the virtio-gpu device) with the amdgpu driver,
  because amdgpu allocates non-compound higher order pages and the tail
  pages could not be mapped into KVM.

  This requires adjusting all uses of struct page in the
  per-architecture code, to always work on the pfn whenever possible.
  The large series that did this, from David Stevens and Sean
  Christopherson, also cleaned up substantially the set of functions
  that provided arch code with the pfn for a host virtual addresses.

  The previous maze of twisty little passages, all different, is
  replaced by five functions (__gfn_to_page, __kvm_faultin_pfn, the
  non-__ versions of these two, and kvm_prefetch_pages) saving almost
  200 lines of code.

  ARM:

   - Support for stage-1 permission indirection (FEAT_S1PIE) and
     permission overlays (FEAT_S1POE), including nested virt + the
     emulated page table walker

   - Introduce PSCI SYSTEM_OFF2 support to KVM + client driver. This
     call was introduced in PSCIv1.3 as a mechanism to request
     hibernation, similar to the S4 state in ACPI

   - Explicitly trap + hide FEAT_MPAM (QoS controls) from KVM guests. As
     part of it, introduce trivial initialization of the host's MPAM
     context so KVM can use the corresponding traps

   - PMU support under nested virtualization, honoring the guest
     hypervisor's trap configuration and event filtering when running a
     nested guest

   - Fixes to vgic ITS serialization where stale device/interrupt table
     entries are not zeroed when the mapping is invalidated by the VM

   - Avoid emulated MMIO completion if userspace has requested
     synchronous external abort injection

   - Various fixes and cleanups affecting pKVM, vCPU initialization, and
     selftests

  LoongArch:

   - Add iocsr and mmio bus simulation in kernel.

   - Add in-kernel interrupt controller emulation.

   - Add support for virtualization extensions to the eiointc irqchip.

  PPC:

   - Drop lingering and utterly obsolete references to PPC970 KVM, which
     was removed 10 years ago.

   - Fix incorrect documentation references to non-existing ioctls

  RISC-V:

   - Accelerate KVM RISC-V when running as a guest

   - Perf support to collect KVM guest statistics from host side

  s390:

   - New selftests: more ucontrol selftests and CPU model sanity checks

   - Support for the gen17 CPU model

   - List registers supported by KVM_GET/SET_ONE_REG in the
     documentation

  x86:

   - Cleanup KVM's handling of Accessed and Dirty bits to dedup code,
     improve documentation, harden against unexpected changes.

     Even if the hardware A/D tracking is disabled, it is possible to
     use the hardware-defined A/D bits to track if a PFN is Accessed
     and/or Dirty, and that removes a lot of special cases.

   - Elide TLB flushes when aging secondary PTEs, as has been done in
     x86's primary MMU for over 10 years.

   - Recover huge pages in-place in the TDP MMU when dirty page logging
     is toggled off, instead of zapping them and waiting until the page
     is re-accessed to create a huge mapping. This reduces vCPU jitter.

   - Batch TLB flushes when dirty page logging is toggled off. This
     reduces the time it takes to disable dirty logging by ~3x.

   - Remove the shrinker that was (poorly) attempting to reclaim shadow
     page tables in low-memory situations.

   - Clean up and optimize KVM's handling of writes to
     MSR_IA32_APICBASE.

   - Advertise CPUIDs for new instructions in Clearwater Forest

   - Quirk KVM's misguided behavior of initialized certain feature MSRs
     to their maximum supported feature set, which can result in KVM
     creating invalid vCPU state. E.g. initializing PERF_CAPABILITIES to
     a non-zero value results in the vCPU having invalid state if
     userspace hides PDCM from the guest, which in turn can lead to
     save/restore failures.

   - Fix KVM's handling of non-canonical checks for vCPUs that support
     LA57 to better follow the "architecture", in quotes because the
     actual behavior is poorly documented. E.g. most MSR writes and
     descriptor table loads ignore CR4.LA57 and operate purely on
     whether the CPU supports LA57.

   - Bypass the register cache when querying CPL from kvm_sched_out(),
     as filling the cache from IRQ context is generally unsafe; harden
     the cache accessors to try to prevent similar issues from occuring
     in the future. The issue that triggered this change was already
     fixed in 6.12, but was still kinda latent.

   - Advertise AMD_IBPB_RET to userspace, and fix a related bug where
     KVM over-advertises SPEC_CTRL when trying to support cross-vendor
     VMs.

   - Minor cleanups

   - Switch hugepage recovery thread to use vhost_task.

     These kthreads can consume significant amounts of CPU time on
     behalf of a VM or in response to how the VM behaves (for example
     how it accesses its memory); therefore KVM tried to place the
     thread in the VM's cgroups and charge the CPU time consumed by that
     work to the VM's container.

     However the kthreads did not process SIGSTOP/SIGCONT, and therefore
     cgroups which had KVM instances inside could not complete freezing.

     Fix this by replacing the kthread with a PF_USER_WORKER thread, via
     the vhost_task abstraction. Another 100+ lines removed, with
     generally better behavior too like having these threads properly
     parented in the process tree.

   - Revert a workaround for an old CPU erratum (Nehalem/Westmere) that
     didn't really work; there was really nothing to work around anyway:
     the broken patch was meant to fix nested virtualization, but the
     PERF_GLOBAL_CTRL MSR is virtualized and therefore unaffected by the
     erratum.

   - Fix 6.12 regression where CONFIG_KVM will be built as a module even
     if asked to be builtin, as long as neither KVM_INTEL nor KVM_AMD is
     'y'.

  x86 selftests:

   - x86 selftests can now use AVX.

  Documentation:

   - Use rST internal links

   - Reorganize the introduction to the API document

  Generic:

   - Protect vcpu->pid accesses outside of vcpu->mutex with a rwlock
     instead of RCU, so that running a vCPU on a different task doesn't
     encounter long due to having to wait for all CPUs become quiescent.

     In general both reads and writes are rare, but userspace that
     supports confidential computing is introducing the use of "helper"
     vCPUs that may jump from one host processor to another. Those will
     be very happy to trigger a synchronize_rcu(), and the effect on
     performance is quite the disaster"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (298 commits)
  KVM: x86: Break CONFIG_KVM_X86's direct dependency on KVM_INTEL || KVM_AMD
  KVM: x86: add back X86_LOCAL_APIC dependency
  Revert "KVM: VMX: Move LOAD_IA32_PERF_GLOBAL_CTRL errata handling out of setup_vmcs_config()"
  KVM: x86: switch hugepage recovery thread to vhost_task
  KVM: x86: expose MSR_PLATFORM_INFO as a feature MSR
  x86: KVM: Advertise CPUIDs for new instructions in Clearwater Forest
  Documentation: KVM: fix malformed table
  irqchip/loongson-eiointc: Add virt extension support
  LoongArch: KVM: Add irqfd support
  LoongArch: KVM: Add PCHPIC user mode read and write functions
  LoongArch: KVM: Add PCHPIC read and write functions
  LoongArch: KVM: Add PCHPIC device support
  LoongArch: KVM: Add EIOINTC user mode read and write functions
  LoongArch: KVM: Add EIOINTC read and write functions
  LoongArch: KVM: Add EIOINTC device support
  LoongArch: KVM: Add IPI user mode read and write function
  LoongArch: KVM: Add IPI read and write function
  LoongArch: KVM: Add IPI device support
  LoongArch: KVM: Add iocsr and mmio bus simulation in kernel
  KVM: arm64: Pass on SVE mapping failures
  ...
2024-11-23 16:00:50 -08:00
Linus Torvalds
0338cd9c22 s390 updates for 6.13 merge window
- Add firmware sysfs interface which allows user space to retrieve the dump
   area size of the machine
 
 - Add 'measurement_chars_full' CHPID sysfs attribute to make the complete
   associated Channel-Measurements Characteristics Block available
 
 - Add virtio-mem support
 
 - Move gmap aka KVM page fault handling from the main fault handler to KVM
   code. This is the first step to make s390 KVM page fault handling similar
   to other architectures. With this first step the main fault handler does
   not have any special handling anymore, and therefore convert it to
   support LOCK_MM_AND_FIND_VMA
 
 - With gcc 14 s390 support for flag output operand support for inline
   assemblies was added. This allows for several optimizations
 
   - Provide a cmpxchg inline assembly which makes use of this, and provide
     all variants of arch_try_cmpxchg() so that the compiler can generate
     slightly better code
 
   - Convert a few cmpxchg() loops to try_cmpxchg() loops
 
   - Similar to x86 add a CC_OUT() helper macro (and other macros), and
     convert all inline assemblies to make use of them, so that depending on
     compiler version better code can be generated
 
 - List installed host-key hashes in sysfs if the machine supports the Query
   Ultravisor Keys UVC
 
 - Add 'Retrieve Secret' ioctl which allows user space in protected
   execution guests to retrieve previously stored secrets from the
   Ultravisor
 
 - Add pkey-uv module which supports the conversion of Ultravisor
   retrievable secrets to protected keys
 
 - Extend the existing paes cipher to exploit the full AES-XTS hardware
   acceleration introduced with message-security assist extension 10
 
 - Convert hopefully all sysfs show functions to use sysfs_emit() so that
   the constant flow of such patches stop
 
 - For PCI devices make use of the newly added Topology ID attribute to
   enable whole card multi-function support despite the change to PCHID per
   port. Additionally improve the overall robustness and usability of
   the multifunction support
 
 - Various other small improvements, fixes, and cleanups
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Merge tag 's390-6.13-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

Pull s390 updates from Heiko Carstens:

 - Add firmware sysfs interface which allows user space to retrieve the
   dump area size of the machine

 - Add 'measurement_chars_full' CHPID sysfs attribute to make the
   complete associated Channel-Measurements Characteristics Block
   available

 - Add virtio-mem support

 - Move gmap aka KVM page fault handling from the main fault handler to
   KVM code. This is the first step to make s390 KVM page fault handling
   similar to other architectures. With this first step the main fault
   handler does not have any special handling anymore, and therefore
   convert it to support LOCK_MM_AND_FIND_VMA

 - With gcc 14 s390 support for flag output operand support for inline
   assemblies was added. This allows for several optimizations:

     - Provide a cmpxchg inline assembly which makes use of this, and
       provide all variants of arch_try_cmpxchg() so that the compiler
       can generate slightly better code

     - Convert a few cmpxchg() loops to try_cmpxchg() loops

     - Similar to x86 add a CC_OUT() helper macro (and other macros),
       and convert all inline assemblies to make use of them, so that
       depending on compiler version better code can be generated

 - List installed host-key hashes in sysfs if the machine supports the
   Query Ultravisor Keys UVC

 - Add 'Retrieve Secret' ioctl which allows user space in protected
   execution guests to retrieve previously stored secrets from the
   Ultravisor

 - Add pkey-uv module which supports the conversion of Ultravisor
   retrievable secrets to protected keys

 - Extend the existing paes cipher to exploit the full AES-XTS hardware
   acceleration introduced with message-security assist extension 10

 - Convert hopefully all sysfs show functions to use sysfs_emit() so
   that the constant flow of such patches stop

 - For PCI devices make use of the newly added Topology ID attribute to
   enable whole card multi-function support despite the change to PCHID
   per port. Additionally improve the overall robustness and usability
   of the multifunction support

 - Various other small improvements, fixes, and cleanups

* tag 's390-6.13-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (133 commits)
  s390/cio/ioasm: Convert to use flag output macros
  s390/cio/qdio: Convert to use flag output macros
  s390/sclp: Convert to use flag output macros
  s390/dasd: Convert to use flag output macros
  s390/boot/physmem: Convert to use flag output macros
  s390/pci: Convert to use flag output macros
  s390/kvm: Convert to use flag output macros
  s390/extmem: Convert to use flag output macros
  s390/string: Convert to use flag output macros
  s390/diag: Convert to use flag output macros
  s390/irq: Convert to use flag output macros
  s390/smp: Convert to use flag output macros
  s390/uv: Convert to use flag output macros
  s390/pai: Convert to use flag output macros
  s390/mm: Convert to use flag output macros
  s390/cpu_mf: Convert to use flag output macros
  s390/cpcmd: Convert to use flag output macros
  s390/topology: Convert to use flag output macros
  s390/time: Convert to use flag output macros
  s390/pageattr: Convert to use flag output macros
  ...
2024-11-18 17:45:41 -08:00
Paolo Bonzini
7b541d557f KVM/arm64 changes for 6.13, part #1
- Support for stage-1 permission indirection (FEAT_S1PIE) and
    permission overlays (FEAT_S1POE), including nested virt + the
    emulated page table walker
 
  - Introduce PSCI SYSTEM_OFF2 support to KVM + client driver. This call
    was introduced in PSCIv1.3 as a mechanism to request hibernation,
    similar to the S4 state in ACPI
 
  - Explicitly trap + hide FEAT_MPAM (QoS controls) from KVM guests. As
    part of it, introduce trivial initialization of the host's MPAM
    context so KVM can use the corresponding traps
 
  - PMU support under nested virtualization, honoring the guest
    hypervisor's trap configuration and event filtering when running a
    nested guest
 
  - Fixes to vgic ITS serialization where stale device/interrupt table
    entries are not zeroed when the mapping is invalidated by the VM
 
  - Avoid emulated MMIO completion if userspace has requested synchronous
    external abort injection
 
  - Various fixes and cleanups affecting pKVM, vCPU initialization, and
    selftests
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Merge tag 'kvmarm-6.13' of https://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD

KVM/arm64 changes for 6.13, part #1

 - Support for stage-1 permission indirection (FEAT_S1PIE) and
   permission overlays (FEAT_S1POE), including nested virt + the
   emulated page table walker

 - Introduce PSCI SYSTEM_OFF2 support to KVM + client driver. This call
   was introduced in PSCIv1.3 as a mechanism to request hibernation,
   similar to the S4 state in ACPI

 - Explicitly trap + hide FEAT_MPAM (QoS controls) from KVM guests. As
   part of it, introduce trivial initialization of the host's MPAM
   context so KVM can use the corresponding traps

 - PMU support under nested virtualization, honoring the guest
   hypervisor's trap configuration and event filtering when running a
   nested guest

 - Fixes to vgic ITS serialization where stale device/interrupt table
   entries are not zeroed when the mapping is invalidated by the VM

 - Avoid emulated MMIO completion if userspace has requested synchronous
   external abort injection

 - Various fixes and cleanups affecting pKVM, vCPU initialization, and
   selftests
2024-11-14 07:05:36 -05:00
Paolo Bonzini
35ff7bfb04 Documentation: KVM: fix malformed table
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Fixes: 5f6a3badbb ("KVM: x86/mmu: Mark page/folio accessed only when zapping leaf SPTEs")
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-11-13 07:20:01 -05:00
Paolo Bonzini
2e9a2c624e Merge branch 'kvm-docs-6.13' into HEAD
- Drop obsolete references to PPC970 KVM, which was removed 10 years ago.

- Fix incorrect references to non-existing ioctls

- List registers supported by KVM_GET/SET_ONE_REG on s390

- Use rST internal links

- Reorganize the introduction to the API document
2024-11-13 07:18:12 -05:00
Paolo Bonzini
bb4409a9e7 KVM x86 misc changes for 6.13
- Clean up and optimize KVM's handling of writes to MSR_IA32_APICBASE.
 
  - Quirk KVM's misguided behavior of initialized certain feature MSRs to
    their maximum supported feature set, which can result in KVM creating
    invalid vCPU state.  E.g. initializing PERF_CAPABILITIES to a non-zero
    value results in the vCPU having invalid state if userspace hides PDCM
    from the guest, which can lead to save/restore failures.
 
  - Fix KVM's handling of non-canonical checks for vCPUs that support LA57
    to better follow the "architecture", in quotes because the actual
    behavior is poorly documented.  E.g. most MSR writes and descriptor
    table loads ignore CR4.LA57 and operate purely on whether the CPU
    supports LA57.
 
  - Bypass the register cache when querying CPL from kvm_sched_out(), as
    filling the cache from IRQ context is generally unsafe, and harden the
    cache accessors to try to prevent similar issues from occuring in the
    future.
 
  - Advertise AMD_IBPB_RET to userspace, and fix a related bug where KVM
    over-advertises SPEC_CTRL when trying to support cross-vendor VMs.
 
  - Minor cleanups
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Merge tag 'kvm-x86-misc-6.13' of https://github.com/kvm-x86/linux into HEAD

KVM x86 misc changes for 6.13

 - Clean up and optimize KVM's handling of writes to MSR_IA32_APICBASE.

 - Quirk KVM's misguided behavior of initialized certain feature MSRs to
   their maximum supported feature set, which can result in KVM creating
   invalid vCPU state.  E.g. initializing PERF_CAPABILITIES to a non-zero
   value results in the vCPU having invalid state if userspace hides PDCM
   from the guest, which can lead to save/restore failures.

 - Fix KVM's handling of non-canonical checks for vCPUs that support LA57
   to better follow the "architecture", in quotes because the actual
   behavior is poorly documented.  E.g. most MSR writes and descriptor
   table loads ignore CR4.LA57 and operate purely on whether the CPU
   supports LA57.

 - Bypass the register cache when querying CPL from kvm_sched_out(), as
   filling the cache from IRQ context is generally unsafe, and harden the
   cache accessors to try to prevent similar issues from occuring in the
   future.

 - Advertise AMD_IBPB_RET to userspace, and fix a related bug where KVM
   over-advertises SPEC_CTRL when trying to support cross-vendor VMs.

 - Minor cleanups
2024-11-13 06:33:00 -05:00
Oliver Upton
7ccd615bc6 Merge branch kvm-arm64/psci-1.3 into kvmarm/next
* kvm-arm64/psci-1.3:
  : PSCI v1.3 support, courtesy of David Woodhouse
  :
  : Bump KVM's PSCI implementation up to v1.3, with the added bonus of
  : implementing the SYSTEM_OFF2 call. Like other system-scoped PSCI calls,
  : this gets relayed to userspace for further processing with a new
  : KVM_SYSTEM_EVENT_SHUTDOWN flag.
  :
  : As an added bonus, implement client-side support for hibernation with
  : the SYSTEM_OFF2 call.
  arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate
  KVM: arm64: nvhe: Pass through PSCI v1.3 SYSTEM_OFF2 call
  KVM: selftests: Add test for PSCI SYSTEM_OFF2
  KVM: arm64: Add support for PSCI v1.2 and v1.3
  KVM: arm64: Add PSCI v1.3 SYSTEM_OFF2 function for hibernation
  firmware/psci: Add definitions for PSCI v1.3 specification

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
2024-11-11 18:36:46 +00:00
Paolo Bonzini
5b47f5a725 Documentation: kvm: reorganize introduction
Reorganize the text to mention file descriptors as early as possible.
Also mention capabilities early as they are a central part of KVM's
API.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241023124507.280382-5-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-11-08 05:57:13 -05:00
Paolo Bonzini
badd5372ec Documentation: kvm: replace section numbers with links
In order to simplify further introduction of hyperlinks, replace explicit
section numbers with rST hyperlinks.  The section numbers could actually
be removed now, but I'm not going to do a huge change throughout the file
for an RFC...

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241023124507.280382-4-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-11-08 05:57:13 -05:00
Paolo Bonzini
aae7527ea9 Documentation: kvm: fix a few mistakes
The only occurrence "Capability: none" actually meant the same as "basic".
Fix that and a few more aesthetic or content issues in the document.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241023124507.280382-3-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-11-08 05:57:13 -05:00
Paolo Bonzini
e16e018e82 KVM: powerpc: remove remaining traces of KVM_CAP_PPC_RMA
This was only needed for PPC970 support, which is long gone: the
implementation was removed in 2014.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241023124507.280382-2-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-11-08 05:57:13 -05:00
David Hildenbrand
e5d94902e4 Documentation: s390-diag.rst: Document diag500(STORAGE LIMIT) subfunction
Let's document our new diag500 subfunction that can be implemented by
userspace.

Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Tested-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Link: https://lore.kernel.org/r/20241025141453.1210600-3-david@redhat.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
2024-11-07 10:26:24 +01:00
David Hildenbrand
b7cfc04548 Documentation: s390-diag.rst: Make diag500 a generic KVM hypercall
Let's make it a generic KVM hypercall, allowing other subfunctions to
be more independent of virtio.

While at it, document that unsupported/unimplemented subfunctions result
in a SPECIFICATION exception.

This is a preparation for documenting a new subfunction.

Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Tested-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Link: https://lore.kernel.org/r/20241025141453.1210600-2-david@redhat.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
2024-11-07 10:26:24 +01:00
Sean Christopherson
dcb988cdac KVM: x86: Quirk initialization of feature MSRs to KVM's max configuration
Add a quirk to control KVM's misguided initialization of select feature
MSRs to KVM's max configuration, as enabling features by default violates
KVM's approach of letting userspace own the vCPU model, and is actively
problematic for MSRs that are conditionally supported, as the vCPU will
end up with an MSR value that userspace can't restore.  E.g. if the vCPU
is configured with PDCM=0, userspace will save and attempt to restore a
non-zero PERF_CAPABILITIES, thanks to KVM's meddling.

Link: https://lore.kernel.org/r/20240802185511.305849-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
2024-11-01 09:22:31 -07:00
Sean Christopherson
0e3b70aa13 KVM: x86: Document an erratum in KVM_SET_VCPU_EVENTS on Intel CPUs
Document a flaw in KVM's ABI which lets userspace attempt to inject a
"bad" hardware exception event, and thus induce VM-Fail on Intel CPUs.
Fixing the flaw is a fool's errand, as AMD doesn't sanity check the
validity of the error code, Intel CPUs that support CET relax the check
for Protected Mode, userspace can change the mode after queueing an
exception, KVM ignores the error code when emulating Real Mode exceptions,
and so on and so forth.

The VM-Fail itself doesn't harm KVM or the kernel beyond triggering a
ratelimited pr_warn(), so just document the oddity.

Link: https://lore.kernel.org/r/20240802200420.330769-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
2024-11-01 09:22:28 -07:00
Sean Christopherson
e2d2ca71ac KVM: Drop @atomic param from gfn=>pfn and hva=>pfn APIs
Drop @atomic from the myriad "to_pfn" APIs now that all callers pass
"false", and remove a comment blurb about KVM running only the "GUP fast"
part in atomic context.

No functional change intended.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-13-seanjc@google.com>
2024-10-25 12:57:58 -04:00
Sean Christopherson
5f6a3badbb KVM: x86/mmu: Mark page/folio accessed only when zapping leaf SPTEs
Now that KVM doesn't clobber Accessed bits of shadow-present SPTEs,
e.g. when prefetching, mark folios as accessed only when zapping leaf
SPTEs, which is a rough heuristic for "only in response to an mmu_notifier
invalidation".  Page aging and LRUs are tolerant of false negatives, i.e.
KVM doesn't need to be precise for correctness, and re-marking folios as
accessed when zapping entire roots or when zapping collapsible SPTEs is
expensive and adds very little value.

E.g. when a VM is dying, all of its memory is being freed; marking folios
accessed at that time provides no known value.  Similarly, because KVM
marks folios as accessed when creating SPTEs, marking all folios as
accessed when userspace happens to delete a memslot doesn't add value.
The folio was marked access when the old SPTE was created, and will be
marked accessed yet again if a vCPU accesses the pfn again after reloading
a new root.  Zapping collapsible SPTEs is a similar story; marking folios
accessed just because userspace disable dirty logging is a side effect of
KVM behavior, not a deliberate goal.

As an intermediate step, a.k.a. bisection point, towards *never* marking
folios accessed when dropping SPTEs, mark folios accessed when the primary
MMU might be invalidating mappings, as such zappings are not KVM initiated,
i.e. might actually be related to page aging and LRU activity.

Note, x86 is the only KVM architecture that "double dips"; every other
arch marks pfns as accessed only when mapping into the guest, not when
mapping into the guest _and_ when removing from the guest.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-10-seanjc@google.com>
2024-10-25 12:54:42 -04:00