Re: [PATCH 4/4] KVM: async_pf: Let host know whether the guest support delivery async_pf as #PF vmexit

Wanpeng Li
2017-06-14T01:01:36Z

2017-06-14 2:19 GMT+08:00 Radim Krčmář <rkrcmar@redhat.com>:
> 2017-06-12 23:08-0700, Wanpeng Li:
>> From: Wanpeng Li <wanpeng.li@hotmail.com>
>>
>> Adds another flag bit (bit 2) to MSR_KVM_ASYNC_PF_EN. If bit 2 is 1, async
>> page faults are delivered to L1 as #PF vmexits; if bit 2 is 0, kvm_can_do_async_pf
>> returns 0 if in guest mode.
>>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: Radim Krčmář <rkrcmar@redhat.com>
>> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
>> ---
>
> I think KVM (L1) should also do something like
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index dd274db9bf77..c15a9f178e60 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -7991,7 +7991,7 @@ static bool nested_vmx_exit_handled(struct kvm_vcpu *vcpu)
> if (is_nmi(intr_info))
> return false;
> else if (is_page_fault(intr_info))
> - return enable_ept;
> + return !vmx->apf_reason && enable_ept;
> else if (is_no_device(intr_info) &&
> !(vmcs12->guest_cr0 & X86_CR0_TS))
> return false;
>
> so it doesn't pass the APF directed towards it (L1) into L2 if there is
> L3 at the moment.

Agreed. I will do this in v2.

Regards,
Wanpeng Li