Re: [RFC PATCH v2 7/7] KVM: KVM: don't break vcpu 'halt' state due to apfs

Xiao Guangrong
2010-11-02T02:25:47Z

On 11/01/2010 08:55 PM, Gleb Natapov wrote:

> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 2cfdf2d..f7aed95 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5295,8 +5295,9 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
> {
> switch(vcpu->arch.mp_state) {
> case KVM_MP_STATE_HALTED:
> - vcpu->arch.mp_state =
> - KVM_MP_STATE_RUNNABLE;
> + if (list_empty_careful(&vcpu->async_pf.done))
> + vcpu->arch.mp_state =
> + KVM_MP_STATE_RUNNABLE;

if nmi/interrupt and apfs completed event occur at the same time, we will miss to
exit halt sate. Maybe we can check the pending event here, see below patch please.

> case KVM_MP_STATE_RUNNABLE:
> vcpu->arch.apf.halted = false;
> break;
> @@ -6279,6 +6280,7 @@ void kvm_arch_async_page_present(struct kvm_vcpu *vcpu,
> vcpu->arch.fault.error_code = 0;
> vcpu->arch.fault.address = work->arch.token;
> kvm_inject_page_fault(vcpu);
> + vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
> }
> }

Have a stupid question, why we make the vcpu runnable here? Sorry i don't know
kvm pv guest to much. :-(

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2044302..27a712b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5267,6 +5267,12 @@ out:
return r;
}

+static bool kvm_vcpu_leave_halt_state(struct kvm_vcpu *vcpu)
+{
+ return vcpu->arch.nmi_pending ||
+ (kvm_arch_interrupt_allowed(vcpu) &&
+ kvm_cpu_has_interrupt(vcpu));
+}

static int __vcpu_run(struct kvm_vcpu *vcpu)
{
@@ -5299,8 +5305,9 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
{
switch(vcpu->arch.mp_state) {
case KVM_MP_STATE_HALTED:
- vcpu->arch.mp_state =
- KVM_MP_STATE_RUNNABLE;
+ if (kvm_vcpu_leave_halt_state(vcpu))
+ vcpu->arch.mp_state =
+ KVM_MP_STATE_RUNNABLE;
case KVM_MP_STATE_RUNNABLE:
vcpu->arch.apf.halted = false;
break;
@@ -6113,9 +6120,7 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
!vcpu->arch.apf.halted)
|| !list_empty_careful(&vcpu->async_pf.done)
|| vcpu->arch.mp_state == KVM_MP_STATE_SIPI_RECEIVED
- || vcpu->arch.nmi_pending ||
- (kvm_arch_interrupt_allowed(vcpu) &&
- kvm_cpu_has_interrupt(vcpu));
+ || kvm_vcpu_leave_halt_state(vcpu);
}

void kvm_vcpu_kick(struct kvm_vcpu *vcpu)