Re: [PATCH 1/2] KVM: x86: Introduce kvm_set_mp_state()

Sean Christopherson
2025-02-12T16:42:30Z

On Mon, Jan 13, 2025, Jim Mattson wrote:
> @@ -11288,7 +11287,7 @@ static int __kvm_emulate_halt(struct kvm_vcpu *vcpu, int state, int reason)
> if (kvm_vcpu_has_events(vcpu))
> vcpu->arch.pv.pv_unhalted = false;
> else
> - vcpu->arch.mp_state = state;
> + kvm_set_mp_state(vcpu, state);

It wouldn't be appropriate in this patch, but I think it makes sense to invoke
kvm_set_mp_state() instead of open coding the pv.pv_unhalted change. E.g. if
the vCPU is somehow not already RUNNABLE (which is a bug?), 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).

Untested, but this? I'll test and post a patch (assuming it works).

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0aca2a5dac7e..c51499c66cfa 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11292,9 +11292,8 @@ 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;