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KVM: arm64: vgic: Explicitly implement vgic_dist::ready ordering

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In preparation to remove synchronize_srcu() from MMIO registration,
remove the distributor's dependency on this implicit barrier by
direct acquire-release synchronization on the flag write and its
lock-free check.

Signed-off-by: Keir Fraser <keirf@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Keir Fraser
2025-09-09 10:00:05 +00:00
committed by Marc Zyngier
parent 8810c6e7cc
commit 11490b5ec6
1 changed files with 2 additions and 9 deletions
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11
arch/arm64/kvm/vgic/vgic-init.c
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@@ -562,7 +562,7 @@ int kvm_vgic_map_resources(struct kvm *kvm)
gpa_t dist_base;
int ret = 0;
if (likely(dist->ready))
if (likely(smp_load_acquire(&dist->ready)))
return 0;
mutex_lock(&kvm->slots_lock);
@@ -593,14 +593,7 @@ int kvm_vgic_map_resources(struct kvm *kvm)
goto out_slots;
}
/*
* kvm_io_bus_register_dev() guarantees all readers see the new MMIO
* registration before returning through synchronize_srcu(), which also
* implies a full memory barrier. As such, marking the distributor as
* 'ready' here is guaranteed to be ordered after all vCPUs having seen
* a completely configured distributor.
*/
dist->ready = true;
smp_store_release(&dist->ready, true);
goto out_slots;
out:
mutex_unlock(&kvm->arch.config_lock);