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Date:   Fri, 9 Feb 2018 16:31:22 -0800 (PST)
From:   Liran Alon <liran.alon@oracle.com>
To:     <chao.gao@intel.com>
Cc:     <mingo@redhat.com>, <x86@kernel.org>, <tglx@linutronix.de>,
        <rkrcmar@redhat.com>, <pbonzini@redhat.com>,
        <linux-kernel@vger.kernel.org>, <hpa@zytor.com>,
        <kvm@vger.kernel.org>
Subject: Re: [PATCH v2] x86/kvm/vmx: Don't halt vcpu when L1 is injecting
 events to L2
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----- chao.gao@intel.com wrote:

> Although L2 is in halt state, it will be in the active state after
> VM entry if the VM entry is vectoring according to SDM 26.6.2
> Activity
> State. Halting the vcpu here means the event won't be injected to L2
> and this decision isn't reported to L1. Thus L0 drops an event that
> should be injected to L2.
>=20
> Cc: Liran Alon <liran.alon@oracle.com>
> Signed-off-by: Chao Gao <chao.gao@intel.com>
> ---
> Changes in v2:
>  - Remove VID stuff. Only handle event injection in this patch.
> ---
>  arch/x86/kvm/vmx.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>=20
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index bb5b488..42f39d9 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -10985,7 +10985,12 @@ static int nested_vmx_run(struct kvm_vcpu
> *vcpu, bool launch)
>  =09if (ret)
>  =09=09return ret;
> =20
> -=09if (vmcs12->guest_activity_state =3D=3D GUEST_ACTIVITY_HLT)
> +=09/*
> +=09 * If we're entering a halted L2 vcpu and the L2 vcpu won't be
> woken
> +=09 * by event injection, halt vcpu for optimization.

I would remove the "for optimization." from the comment.

> +=09 */
> +=09if ((vmcs12->guest_activity_state =3D=3D GUEST_ACTIVITY_HLT) &&
> +=09    !(vmcs12->vm_entry_intr_info_field &
> VECTORING_INFO_VALID_MASK))

VECTORING_INFO_VALID_MASK is used in KVM code against vmcs12->idt_vectoring=
_info_field.
I think you should use INTR_INFO_VALID_MASK to be consistent with rest of c=
ode.

>  =09=09return kvm_vcpu_halt(vcpu);
> =20
>  =09vmx->nested.nested_run_pending =3D 1;
> --=20
> 1.9.1

In addition, commit title should be written in format of:
"KVM: VMX: Don't halt vcpu when L1 is injecting events to L2"
(Makes it easier to grep in git log).

Other than that, seems good to me. :)

Reviewed-by: Liran Alon <liran.alon@oracle.com>

Thanks,
-Liran