linux-kernel - Re: [PATCH v2] KVM: apic: reuse smp_wmb() in kvm_make

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Message-ID: <4202948e-1c12-9ab0-5bba-d63846da8001@redhat.com>
Date:   Wed, 12 Feb 2020 12:55:36 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linmiaohe <linmiaohe@...wei.com>, rkrcmar@...hat.com,
        sean.j.christopherson@...el.com, vkuznets@...hat.com,
        wanpengli@...cent.com, jmattson@...gle.com, joro@...tes.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v2] KVM: apic: reuse smp_wmb() in kvm_make_request()

On 07/02/20 16:22, linmiaohe wrote:
> From: Miaohe Lin <linmiaohe@...wei.com>
> 
> kvm_make_request() provides smp_wmb() so pending_events changes are
> guaranteed to be visible.
> 
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> ---
> v1->v2:
> Collected Vitaly's R-b
> Use Vitaly's alternative wording
> Drop unnecessary comment as suggested by Sean Christopherson
> ---
>  arch/x86/kvm/lapic.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index eafc631d305c..afcd30d44cbb 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1080,9 +1080,6 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
>  			result = 1;
>  			/* assumes that there are only KVM_APIC_INIT/SIPI */
>  			apic->pending_events = (1UL << KVM_APIC_INIT);
> -			/* make sure pending_events is visible before sending
> -			 * the request */
> -			smp_wmb();
>  			kvm_make_request(KVM_REQ_EVENT, vcpu);
>  			kvm_vcpu_kick(vcpu);
>  		}
> 


Queued, thanks.

Paolo