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 11:05:46 +0800
From:	Yang Zhang <yang.zhang.wz@...il.com>
To:	Feng Wu <feng.wu@...el.com>, pbonzini@...hat.com,
	rkrcmar@...hat.com
Cc:	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

On 2016/1/20 9:42, Feng Wu wrote:
> 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>
> ---
>   arch/x86/kvm/vmx.c | 11 ++++++++++-
>   1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index e2951b6..13d14d4 100644
> --- 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,
>   		 */
>
>   		kvm_set_msi_irq(e, &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));
> +			ret = irq_set_vcpu_affinity(host_irq, NULL);
> +			pi_clear_sn(vcpu_to_pi_desc(vcpu));
> +
>   			continue;
> +		}
>
>   		vcpu_info.pi_desc_addr = __pa(vcpu_to_pi_desc(vcpu));
>   		vcpu_info.vector = irq.vector;
>

I am still feel weird with this change: according the semantic of VT-d 
posted interrupt, the interrupt will injected to guest through posted 
notification and /proc/interrupts shows the same meaning. But now, 
without being aware of user, the interrupt changes to legacy way and it 
appears on different entry on /proc/interrupts. It looks weird.

Any comments? Paolo.

-- 
best regards
yang