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linux/arch/x86/kvm/cpuid.h
Sean Christopherson 8f2a27752e KVM: x86: Replace (almost) all guest CPUID feature queries with cpu_caps 
Switch all queries (except XSAVES) of guest features from guest CPUID to
guest capabilities, i.e. replace all calls to guest_cpuid_has() with calls
to guest_cpu_cap_has().

Keep guest_cpuid_has() around for XSAVES, but subsume its helper
guest_cpuid_get_register() and add a compile-time assertion to prevent
using guest_cpuid_has() for any other feature.  Add yet another comment
for XSAVE to explain why KVM is allowed to query its raw guest CPUID.

Opportunistically drop the unused guest_cpuid_clear(), as there should be
no circumstance in which KVM needs to _clear_ a guest CPUID feature now
that everything is tracked via cpu_caps.  E.g. KVM may need to _change_
a feature to emulate dynamic CPUID flags, but KVM should never need to
clear a feature in guest CPUID to prevent it from being used by the guest.

Delete the last remnants of the governed features framework, as the lone
holdout was vmx_adjust_secondary_exec_control()'s divergent behavior for
governed vs. ungoverned features.

Note, replacing guest_cpuid_has() checks with guest_cpu_cap_has() when
computing reserved CR4 bits is a nop when viewed as a whole, as KVM's
capabilities are already incorporated into the calculation, i.e. if a
feature is present in guest CPUID but unsupported by KVM, its CR4 bit
was already being marked as reserved, checking guest_cpu_cap_has() simply
double-stamps that it's a reserved bit.

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20241128013424.4096668-51-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
2024-12-18 14:20:15 -08:00

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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef ARCH_X86_KVM_CPUID_H
#define ARCH_X86_KVM_CPUID_H
#include "reverse_cpuid.h"
#include <asm/cpu.h>
#include <asm/processor.h>
#include <uapi/asm/kvm_para.h>
extern u32 kvm_cpu_caps[NR_KVM_CPU_CAPS] __read_mostly;
void kvm_set_cpu_caps(void);
void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu);
void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu);
struct kvm_cpuid_entry2 *kvm_find_cpuid_entry_index(struct kvm_vcpu *vcpu,
u32 function, u32 index);
struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,
u32 function);
int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,
struct kvm_cpuid_entry2 __user *entries,
unsigned int type);
int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
struct kvm_cpuid *cpuid,
struct kvm_cpuid_entry __user *entries);
int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
struct kvm_cpuid2 *cpuid,
struct kvm_cpuid_entry2 __user *entries);
int kvm_vcpu_ioctl_get_cpuid2(struct kvm_vcpu *vcpu,
struct kvm_cpuid2 *cpuid,
struct kvm_cpuid_entry2 __user *entries);
bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,
u32 *ecx, u32 *edx, bool exact_only);
void __init kvm_init_xstate_sizes(void);
u32 xstate_required_size(u64 xstate_bv, bool compacted);
int cpuid_query_maxphyaddr(struct kvm_vcpu *vcpu);
u64 kvm_vcpu_reserved_gpa_bits_raw(struct kvm_vcpu *vcpu);
static inline int cpuid_maxphyaddr(struct kvm_vcpu *vcpu)
{
return vcpu->arch.maxphyaddr;
}
static inline bool kvm_vcpu_is_legal_gpa(struct kvm_vcpu *vcpu, gpa_t gpa)
{
return !(gpa & vcpu->arch.reserved_gpa_bits);
}
static inline bool kvm_vcpu_is_legal_aligned_gpa(struct kvm_vcpu *vcpu,
gpa_t gpa, gpa_t alignment)
{
return IS_ALIGNED(gpa, alignment) && kvm_vcpu_is_legal_gpa(vcpu, gpa);
}
static inline bool page_address_valid(struct kvm_vcpu *vcpu, gpa_t gpa)
{
return kvm_vcpu_is_legal_aligned_gpa(vcpu, gpa, PAGE_SIZE);
}
static __always_inline void cpuid_entry_override(struct kvm_cpuid_entry2 *entry,
unsigned int leaf)
{
u32 *reg = cpuid_entry_get_reg(entry, leaf * 32);
BUILD_BUG_ON(leaf >= ARRAY_SIZE(kvm_cpu_caps));
*reg = kvm_cpu_caps[leaf];
}
static __always_inline bool guest_cpuid_has(struct kvm_vcpu *vcpu,
unsigned int x86_feature)
{
const struct cpuid_reg cpuid = x86_feature_cpuid(x86_feature);
struct kvm_cpuid_entry2 *entry;
u32 *reg;
/*
* XSAVES is a special snowflake. Due to lack of a dedicated intercept
* on SVM, KVM must assume that XSAVES (and thus XRSTORS) is usable by
* the guest if the host supports XSAVES and *XSAVE* is exposed to the
* guest. Because the guest can execute XSAVES and XRSTORS, i.e. can
* indirectly consume XSS, KVM must ensure XSS is zeroed when running
* the guest, i.e. must set XSAVES in vCPU capabilities. But to reject
* direct XSS reads and writes (to minimize the virtualization hole and
* honor userspace's CPUID), KVM needs to check the raw guest CPUID,
* not KVM's view of guest capabilities.
*
* For all other features, guest capabilities are accurate. Expand
* this allowlist with extreme vigilance.
*/
BUILD_BUG_ON(x86_feature != X86_FEATURE_XSAVES);
entry = kvm_find_cpuid_entry_index(vcpu, cpuid.function, cpuid.index);
if (!entry)
return NULL;
reg = __cpuid_entry_get_reg(entry, cpuid.reg);
if (!reg)
return false;
return *reg & __feature_bit(x86_feature);
}
static inline bool guest_cpuid_is_amd_compatible(struct kvm_vcpu *vcpu)
{
return vcpu->arch.is_amd_compatible;
}
static inline bool guest_cpuid_is_intel_compatible(struct kvm_vcpu *vcpu)
{
return !guest_cpuid_is_amd_compatible(vcpu);
}
static inline int guest_cpuid_family(struct kvm_vcpu *vcpu)
{
struct kvm_cpuid_entry2 *best;
best = kvm_find_cpuid_entry(vcpu, 0x1);
if (!best)
return -1;
return x86_family(best->eax);
}
static inline int guest_cpuid_model(struct kvm_vcpu *vcpu)
{
struct kvm_cpuid_entry2 *best;
best = kvm_find_cpuid_entry(vcpu, 0x1);
if (!best)
return -1;
return x86_model(best->eax);
}
static inline bool cpuid_model_is_consistent(struct kvm_vcpu *vcpu)
{
return boot_cpu_data.x86_model == guest_cpuid_model(vcpu);
}
static inline int guest_cpuid_stepping(struct kvm_vcpu *vcpu)
{
struct kvm_cpuid_entry2 *best;
best = kvm_find_cpuid_entry(vcpu, 0x1);
if (!best)
return -1;
return x86_stepping(best->eax);
}
static inline bool supports_cpuid_fault(struct kvm_vcpu *vcpu)
{
return vcpu->arch.msr_platform_info & MSR_PLATFORM_INFO_CPUID_FAULT;
}
static inline bool cpuid_fault_enabled(struct kvm_vcpu *vcpu)
{
return vcpu->arch.msr_misc_features_enables &
MSR_MISC_FEATURES_ENABLES_CPUID_FAULT;
}
static __always_inline void kvm_cpu_cap_clear(unsigned int x86_feature)
{
unsigned int x86_leaf = __feature_leaf(x86_feature);
kvm_cpu_caps[x86_leaf] &= ~__feature_bit(x86_feature);
}
static __always_inline void kvm_cpu_cap_set(unsigned int x86_feature)
{
unsigned int x86_leaf = __feature_leaf(x86_feature);
kvm_cpu_caps[x86_leaf] |= __feature_bit(x86_feature);
}
static __always_inline u32 kvm_cpu_cap_get(unsigned int x86_feature)
{
unsigned int x86_leaf = __feature_leaf(x86_feature);
return kvm_cpu_caps[x86_leaf] & __feature_bit(x86_feature);
}
static __always_inline bool kvm_cpu_cap_has(unsigned int x86_feature)
{
return !!kvm_cpu_cap_get(x86_feature);
}
static __always_inline void kvm_cpu_cap_check_and_set(unsigned int x86_feature)
{
if (boot_cpu_has(x86_feature))
kvm_cpu_cap_set(x86_feature);
}
static __always_inline bool guest_pv_has(struct kvm_vcpu *vcpu,
unsigned int kvm_feature)
{
if (!vcpu->arch.pv_cpuid.enforce)
return true;
return vcpu->arch.pv_cpuid.features & (1u << kvm_feature);
}
static __always_inline void guest_cpu_cap_set(struct kvm_vcpu *vcpu,
unsigned int x86_feature)
{
unsigned int x86_leaf = __feature_leaf(x86_feature);
vcpu->arch.cpu_caps[x86_leaf] |= __feature_bit(x86_feature);
}
static __always_inline void guest_cpu_cap_clear(struct kvm_vcpu *vcpu,
unsigned int x86_feature)
{
unsigned int x86_leaf = __feature_leaf(x86_feature);
vcpu->arch.cpu_caps[x86_leaf] &= ~__feature_bit(x86_feature);
}
static __always_inline void guest_cpu_cap_change(struct kvm_vcpu *vcpu,
unsigned int x86_feature,
bool guest_has_cap)
{
if (guest_has_cap)
guest_cpu_cap_set(vcpu, x86_feature);
else
guest_cpu_cap_clear(vcpu, x86_feature);
}
static __always_inline bool guest_cpu_cap_has(struct kvm_vcpu *vcpu,
unsigned int x86_feature)
{
unsigned int x86_leaf = __feature_leaf(x86_feature);
return vcpu->arch.cpu_caps[x86_leaf] & __feature_bit(x86_feature);
}
static inline bool kvm_vcpu_is_legal_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
{
if (guest_cpu_cap_has(vcpu, X86_FEATURE_LAM))
cr3 &= ~(X86_CR3_LAM_U48 | X86_CR3_LAM_U57);
return kvm_vcpu_is_legal_gpa(vcpu, cr3);
}
static inline bool guest_has_spec_ctrl_msr(struct kvm_vcpu *vcpu)
{
return (guest_cpu_cap_has(vcpu, X86_FEATURE_SPEC_CTRL) ||
guest_cpu_cap_has(vcpu, X86_FEATURE_AMD_STIBP) ||
guest_cpu_cap_has(vcpu, X86_FEATURE_AMD_IBRS) ||
guest_cpu_cap_has(vcpu, X86_FEATURE_AMD_SSBD));
}
static inline bool guest_has_pred_cmd_msr(struct kvm_vcpu *vcpu)
{
return (guest_cpu_cap_has(vcpu, X86_FEATURE_SPEC_CTRL) ||
guest_cpu_cap_has(vcpu, X86_FEATURE_AMD_IBPB) ||
guest_cpu_cap_has(vcpu, X86_FEATURE_SBPB));
}
#endif
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