Messages in this thread Patch in this message | | | Date | Tue, 9 Jan 2024 17:27:01 -0800 | Subject | [PATCH 2/6] KVM: VMX: Re-enter guest in fastpath for "spurious" preemption timer exits | From | Sean Christopherson <> |
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Re-enter the guest in the fast path if VMX preeemption timer VM-Exit was "spurious", i.e. if KVM "soft disabled" the timer by writing -1u and by some miracle the timer expired before any other VM-Exit occurred. This is just an intermediate step to cleaning up the preemption timer handling, optimizing these types of spurious VM-Exits is not interesting as they are extremely rare/infrequent.
Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kvm/vmx/vmx.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 51d0f3985463..4caad881d9a0 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -5995,8 +5995,15 @@ static fastpath_t handle_fastpath_preemption_timer(struct kvm_vcpu *vcpu) { struct vcpu_vmx *vmx = to_vmx(vcpu); - if (!vmx->req_immediate_exit && - !unlikely(vmx->loaded_vmcs->hv_timer_soft_disabled)) { + /* + * In the *extremely* unlikely scenario that this is a spurious VM-Exit + * due to the timer expiring while it was "soft" disabled, just eat the + * exit and re-enter the guest. + */ + if (unlikely(vmx->loaded_vmcs->hv_timer_soft_disabled)) + return EXIT_FASTPATH_REENTER_GUEST; + + if (!vmx->req_immediate_exit) { kvm_lapic_expired_hv_timer(vcpu); return EXIT_FASTPATH_REENTER_GUEST; } -- 2.43.0.472.g3155946c3a-goog
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