linux-kernel - Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the interrupt is not single-destination

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Date:	Thu, 21 Jan 2016 17:19:50 +0100
From:	Radim Krčmář <rkrcmar@...hat.com>
To:	Feng Wu <feng.wu@...el.com>
Cc:	pbonzini@...hat.com, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Subject: Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the
 interrupt is not single-destination

2016-01-20 09:42+0800, Feng Wu:
> When the interrupt is not single destination any more, we need
> to change back IRTE to remapped mode explicitly.
> 
> Signed-off-by: Feng Wu <feng.wu@...el.com>
> ---
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> @@ -10764,8 +10764,17 @@ static int vmx_update_pi_irte(struct kvm *kvm, unsigned int host_irq,
> -		if (!kvm_intr_is_single_vcpu(kvm, &irq, &vcpu))
> +		if (!kvm_intr_is_single_vcpu(kvm, &irq, &vcpu)) {
> +			/*
> +			 * Make sure the IRTE is in remapped mode if
> +			 * we don't handle it in posted mode.
> +			 */
> +			pi_set_sn(vcpu_to_pi_desc(vcpu));

What could go wrong if we didn't suppress notifications here?

Thanks.

> +			ret = irq_set_vcpu_affinity(host_irq, NULL);
> +			pi_clear_sn(vcpu_to_pi_desc(vcpu));
> +
>  			continue;
> +		}