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KVM: x86: Ensure vcpu->mode is loaded from memory in kvm_vcpu_exit_request()

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Wrap kvm_vcpu_exit_request()'s load of vcpu->mode with READ_ONCE() to
ensure the variable is re-loaded from memory, as there is no guarantee the
caller provides the necessary annotations to ensure KVM sees a fresh value,
e.g. the VM-Exit fastpath could theoretically reuse the pre-VM-Enter value.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/20240828232013.768446-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2024-08-28 16:20:13 -07:00
parent 6e44d2427b
commit 3ffe874ea3
1 changed files with 3 additions and 2 deletions
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5
arch/x86/kvm/x86.c
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@ -2144,8 +2144,9 @@ EXPORT_SYMBOL_GPL(kvm_emulate_monitor);
static inline bool kvm_vcpu_exit_request(struct kvm_vcpu *vcpu)
{
xfer_to_guest_mode_prepare();
return vcpu->mode == EXITING_GUEST_MODE || kvm_request_pending(vcpu) ||
xfer_to_guest_mode_work_pending();
return READ_ONCE(vcpu->mode) == EXITING_GUEST_MODE ||
kvm_request_pending(vcpu) || xfer_to_guest_mode_work_pending();
}
/*