| Message ID | 20250224174156.2362059-1-seanjc@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | KVM: x86: Always set mp_state to RUNNABLE on wakeup from HLT | expand |
On Mon, 24 Feb 2025 09:41:56 -0800, Sean Christopherson wrote: > When emulating HLT and a wake event is already pending, explicitly mark > the vCPU RUNNABLE (via kvm_set_mp_state()) instead of assuming the vCPU is > already in the appropriate state. Barring a KVM bug, it should be > impossible for the vCPU to be in a non-RUNNABLE state, but there is no > advantage to relying on that to hold true, and ensuring the vCPU is made > RUNNABLE avoids non-deterministic behavior with respect to pv_unhalted. > > [...] Applied to kvm-x86 misc, thanks! [1/1] KVM: x86: Always set mp_state to RUNNABLE on wakeup from HLT https://github.com/kvm-x86/linux/commit/2a289aed3fcd -- https://github.com/kvm-x86/linux/tree/next
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 58b82d6fd77c..7f5abdaab935 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -11310,9 +11310,8 @@ static int __kvm_emulate_halt(struct kvm_vcpu *vcpu, int state, int reason) ++vcpu->stat.halt_exits; if (lapic_in_kernel(vcpu)) { if (kvm_vcpu_has_events(vcpu)) - vcpu->arch.pv.pv_unhalted = false; - else - kvm_set_mp_state(vcpu, state); + state = KVM_MP_STATE_RUNNABLE; + kvm_set_mp_state(vcpu, state); return 1; } else { vcpu->run->exit_reason = reason;
When emulating HLT and a wake event is already pending, explicitly mark the vCPU RUNNABLE (via kvm_set_mp_state()) instead of assuming the vCPU is already in the appropriate state. Barring a KVM bug, it should be impossible for the vCPU to be in a non-RUNNABLE state, but there is no advantage to relying on that to hold true, and ensuring the vCPU is made RUNNABLE avoids non-deterministic behavior with respect to pv_unhalted. E.g. if the vCPU is not already RUNNABLE, then depending on when pv_unhalted is set, KVM could either leave the vCPU in the non-RUNNABLE state (set before __kvm_emulate_halt()), or transition the vCPU to HALTED and then RUNNABLE (pv_unhalted set after the kvm_vcpu_has_events() check). Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kvm/x86.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) base-commit: fed48e2967f402f561d80075a20c5c9e16866e53