linux-kernel - Re: [PATCH MANUALSEL 5.10 2/4] KVM: VMX: clear vmx_x86_ops.sync_pir_to

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Message-ID: <283f2ad2-2991-38fb-2d9d-51230c7994f0@redhat.com>
Date:   Mon, 13 Dec 2021 15:29:02 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, kvm@...r.kernel.org
Subject: Re: [PATCH MANUALSEL 5.10 2/4] KVM: VMX: clear
 vmx_x86_ops.sync_pir_to_irr if APICv is disabled

On 12/13/21 15:20, Sasha Levin wrote:
> From: Paolo Bonzini <pbonzini@...hat.com>
> 
> [ Upstream commit e90e51d5f01d2baae5dcce280866bbb96816e978 ]
> 
> There is nothing to synchronize if APICv is disabled, since neither
> other vCPUs nor assigned devices can set PIR.ON.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>   arch/x86/kvm/vmx/vmx.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 5b7664d51dc2b..dff8ab5a53280 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7814,10 +7814,10 @@ static __init int hardware_setup(void)
>   		ple_window_shrink = 0;
>   	}
>   
> -	if (!cpu_has_vmx_apicv()) {
> +	if (!cpu_has_vmx_apicv())
>   		enable_apicv = 0;
> +	if (!enable_apicv)
>   		vmx_x86_ops.sync_pir_to_irr = NULL;
> -	}
>   
>   	if (cpu_has_vmx_tsc_scaling()) {
>   		kvm_has_tsc_control = true;
> 

NACK - the patch is only okay to backport for 5.15

Paolo