linux-kernel - Re: [PATCH v4 11/15] KVM: SVM: Do not throw warning when calling avic_vcpu

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Date:   Mon, 9 May 2022 15:40:00 +0200
From:   "Gupta, Pankaj" <pankaj.gupta@....com>
To:     Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     pbonzini@...hat.com, mlevitsk@...hat.com, seanjc@...gle.com,
        joro@...tes.org, jon.grimm@....com, wei.huang2@....com,
        terry.bowman@....com
Subject: Re: [PATCH v4 11/15] KVM: SVM: Do not throw warning when calling
 avic_vcpu_load on a running vcpu

On 5/8/2022 4:39 AM, Suravee Suthikulpanit wrote:
> Originalliy, this WARN_ON is designed to detect when calling
> avic_vcpu_load() on an already running vcpu in AVIC mode (i.e. the AVIC
> is_running bit is set).
> 
> However, for x2AVIC, the vCPU can switch from xAPIC to x2APIC mode while in
> running state, in which the avic_vcpu_load() will be called from
> svm_refresh_apicv_exec_ctrl().
> 
> Therefore, remove this warning since it is no longer appropriate.
> 
> Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
> ---
>   arch/x86/kvm/svm/avic.c | 1 -
>   1 file changed, 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> index ad2ef6c00559..8e90c659de2d 100644
> --- a/arch/x86/kvm/svm/avic.c
> +++ b/arch/x86/kvm/svm/avic.c
> @@ -1059,7 +1059,6 @@ void __avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>   		return;
>   
>   	entry = READ_ONCE(*(svm->avic_physical_id_cache));
> -	WARN_ON(entry & AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK);
>   
>   	entry &= ~AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK;
>   	entry |= (h_physical_id & AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK);

Looks good to me.

Reviewed-by: Pankaj Gupta <pankaj.gupta@....com>