linux-kernel - Re: [PATCH] x86/kvm/vmx: Don't halt vcpu when L1 is injecting events to L2

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Message-ID: <7de4e758-08cc-2c45-b0aa-dfe28dfef398@redhat.com>
Date:   Thu, 8 Feb 2018 11:29:49 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Chao Gao <chao.gao@...el.com>, kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Liran Alon <liran.alon@...cle.com>
Subject: Re: [PATCH] x86/kvm/vmx: Don't halt vcpu when L1 is injecting events
 to L2

On 08/02/2018 06:13, Chao Gao wrote:
> Although L2 is in halt state, it will be in the active state after
> VM entry if the VM entry is vectoring. 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.
> 
> Because virtual interrupt delivery may wake L2 vcpu, if VID is enabled,
> do the same thing -- don't halt L2.

This second part seems wrong to me, or at least overly general.  Perhaps
you mean if RVI>0?

Thanks,

Paolo

> Signed-off-by: Chao Gao <chao.gao@...el.com>
> ---
>  arch/x86/kvm/vmx.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index bb5b488..e1fe4e4 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -10985,8 +10985,14 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
>  	if (ret)
>  		return ret;
>  
> -	if (vmcs12->guest_activity_state == GUEST_ACTIVITY_HLT)
> -		return kvm_vcpu_halt(vcpu);
> +	if (vmcs12->guest_activity_state == GUEST_ACTIVITY_HLT) {
> +		u32 intr_info = vmcs_read32(VM_ENTRY_INTR_INFO_FIELD);
> +		u32 exec_control = vmcs_read32(SECONDARY_VM_EXEC_CONTROL);
> +
> +		if (!(intr_info & VECTORING_INFO_VALID_MASK) &&
> +			!(exec_control & SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY))
> +			return kvm_vcpu_halt(vcpu);
> +	}

>  	vmx->nested.nested_run_pending = 1;
>  
>