linux-kernel - Re: [PATCH] KVM: x86: Sync the pending Posted-Interrupts

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Message-ID: <20190125163329.GA41385@Konrads-MacBook-Pro.local>
Date:   Fri, 25 Jan 2019 11:33:36 -0500
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     Luwei Kang <luwei.kang@...el.com>
Cc:     kvm@...r.kernel.org, pbonzini@...hat.com, rkrcmar@...hat.com,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: x86: Sync the pending Posted-Interrupts

On Fri, Jan 18, 2019 at 02:34:00PM +0800, Luwei Kang wrote:
> Some Posted-Interrupts from passthrough devices may be lost or
> overwritten when the vCPU is in runnable state.
> 
> The SN (Suppress Notification) of PID (Posted Interrupt Descriptor) will
> be set when the vCPU is preempted (vCPU in KVM_MP_STATE_RUNNABLE state
> but not running on physical CPU). If a posted interrupt coming at this
> time, the irq remmaping facility will set the bit of PIR (Posted
> Interrupt Requests) but ON (Outstanding Notification).

s/but ON/and ON is set too/?
> So this interrupt can't be sync to APIC virtualization register and
> will not be handled by Guest because ON is zero.
> 
> Signed-off-by: Luwei Kang <luwei.kang@...el.com>
> ---
>  arch/x86/kvm/vmx/vmx.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index f6915f1..820a03b 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -6048,7 +6048,7 @@ static int vmx_sync_pir_to_irr(struct kvm_vcpu *vcpu)
>  	bool max_irr_updated;
>  
>  	WARN_ON(!vcpu->arch.apicv_active);
> -	if (pi_test_on(&vmx->pi_desc)) {
> +	if (!bitmap_empty((unsigned long *)vmx->pi_desc.pir, NR_VECTORS)) {
>  		pi_clear_on(&vmx->pi_desc);
>  		/*
>  		 * IOMMU can write to PIR.ON, so the barrier matters even on UP.