netdev - Re: [PATCH 1/2] KVM: not register a IRQ bypass producer if unsupported or disabled

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Date:   Tue, 20 Oct 2020 14:23:14 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Zhenzhong Duan <zhenzhong.duan@...il.com>,
        linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org
Cc:     netdev@...r.kernel.org, pbonzini@...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, mst@...hat.com
Subject: Re: [PATCH 1/2] KVM: not register a IRQ bypass producer if
 unsupported or disabled


On 2020/10/19 下午5:06, Zhenzhong Duan wrote:
> If Post interrupt is disabled due to hardware limit or forcely disabled
> by "intremap=nopost" parameter, return -EINVAL so that the legacy mode IRQ
> isn't registered as IRQ bypass producer.


Is there any side effect if it was still registered?


>
> With this change, below message is printed:
> "vfio-pci 0000:db:00.0: irq bypass producer (token 0000000060c8cda5) registration fails: -22"


I may miss something, but the patch only touches vhost-vDPA instead of VFIO?

Thanks


>
> ..which also hints us if a vfio or vdpa device works in PI mode or legacy
> remapping mode.
>
> Add a print to vdpa code just like what vfio_msi_set_vector_signal() does.
>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@...il.com>
> ---
>   arch/x86/kvm/svm/avic.c | 3 +--
>   arch/x86/kvm/vmx/vmx.c  | 5 ++---
>   drivers/vhost/vdpa.c    | 5 +++++
>   3 files changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> index ac830cd..316142a 100644
> --- a/arch/x86/kvm/svm/avic.c
> +++ b/arch/x86/kvm/svm/avic.c
> @@ -814,7 +814,7 @@ int svm_update_pi_irte(struct kvm *kvm, unsigned int host_irq,
>   
>   	if (!kvm_arch_has_assigned_device(kvm) ||
>   	    !irq_remapping_cap(IRQ_POSTING_CAP))
> -		return 0;
> +		return ret;
>   
>   	pr_debug("SVM: %s: host_irq=%#x, guest_irq=%#x, set=%#x\n",
>   		 __func__, host_irq, guest_irq, set);
> @@ -899,7 +899,6 @@ int svm_update_pi_irte(struct kvm *kvm, unsigned int host_irq,
>   		}
>   	}
>   
> -	ret = 0;
>   out:
>   	srcu_read_unlock(&kvm->irq_srcu, idx);
>   	return ret;
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index f0a9954..1fed6d6 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7716,12 +7716,12 @@ static int vmx_update_pi_irte(struct kvm *kvm, unsigned int host_irq,
>   	struct kvm_lapic_irq irq;
>   	struct kvm_vcpu *vcpu;
>   	struct vcpu_data vcpu_info;
> -	int idx, ret = 0;
> +	int idx, ret = -EINVAL;
>   
>   	if (!kvm_arch_has_assigned_device(kvm) ||
>   		!irq_remapping_cap(IRQ_POSTING_CAP) ||
>   		!kvm_vcpu_apicv_active(kvm->vcpus[0]))
> -		return 0;
> +		return ret;
>   
>   	idx = srcu_read_lock(&kvm->irq_srcu);
>   	irq_rt = srcu_dereference(kvm->irq_routing, &kvm->irq_srcu);
> @@ -7787,7 +7787,6 @@ static int vmx_update_pi_irte(struct kvm *kvm, unsigned int host_irq,
>   		}
>   	}
>   
> -	ret = 0;
>   out:
>   	srcu_read_unlock(&kvm->irq_srcu, idx);
>   	return ret;
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 62a9bb0..b20060a 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -107,6 +107,11 @@ static void vhost_vdpa_setup_vq_irq(struct vhost_vdpa *v, u16 qid)
>   	vq->call_ctx.producer.token = vq->call_ctx.ctx;
>   	vq->call_ctx.producer.irq = irq;
>   	ret = irq_bypass_register_producer(&vq->call_ctx.producer);
> +	if (unlikely(ret))
> +		dev_info(&vdpa->dev,
> +		"irq bypass producer (token %p) registration fails: %d\n",
> +		vq->call_ctx.producer.token, ret);
> +
>   	spin_unlock(&vq->call_ctx.ctx_lock);
>   }
>