linux-kernel - Re: [PATCH 1/4] KVM: x86: ignore APICv if LAPIC is not enabled

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Date:   Thu, 25 Nov 2021 01:36:54 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH 1/4] KVM: x86: ignore APICv if LAPIC is not enabled

On Mon, Nov 22, 2021, Paolo Bonzini wrote:
> Synchronize the condition for the two calls to kvm_x86_sync_pir_to_irr.
> The one in the reenter-guest fast path invoked the callback
> unconditionally even if LAPIC is disabled.
> 
> Cc: stable@...r.kernel.org
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  arch/x86/kvm/x86.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 5a403d92833f..441f4769173e 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -9849,7 +9849,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
>  		if (likely(exit_fastpath != EXIT_FASTPATH_REENTER_GUEST))
>  			break;
>  
> -		if (vcpu->arch.apicv_active)
> +		if (kvm_lapic_enabled(vcpu) && vcpu->arch.apicv_active)

Ooooh, lapic _enabled_, not just present.  That took me far too long to read...

Reviewed-by: Sean Christopherson <seanjc@...gle.com>

>  			static_call(kvm_x86_sync_pir_to_irr)(vcpu);
>  
>  		if (unlikely(kvm_vcpu_exit_request(vcpu))) {
> -- 
> 2.27.0
> 
>