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From:   Zhenzhong Duan <zhenzhong.duan@gmail.com>
Date:   Tue, 20 Oct 2020 18:05:16 +0800
Message-ID: <CAFH1YnNsoPeOe6fVZOasy_GiLE7-tiSKeezSEoxv4+wTU+FUAg@mail.gmail.com>
Subject: Re: [PATCH 1/2] KVM: not register a IRQ bypass producer if
 unsupported or disabled
To:     Jason Wang <jasowang@redhat.com>
Cc:     linux-kernel <linux-kernel@vger.kernel.org>,
        virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
        netdev@vger.kernel.org, pbonzini@redhat.com,
        sean.j.christopherson@intel.com, vkuznets@redhat.com,
        wanpengli@tencent.com, jmattson@google.com,
        Joerg Roedel <joro@8bytes.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        mst@redhat.com
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On Tue, Oct 20, 2020 at 2:23 PM Jason Wang <jasowang@redhat.com> wrote:
>
>
> On 2020/10/19 =E4=B8=8B=E5=8D=885:06, Zhenzhong Duan wrote:
> > If Post interrupt is disabled due to hardware limit or forcely disabled
> > by "intremap=3Dnopost" parameter, return -EINVAL so that the legacy mod=
e IRQ
> > isn't registered as IRQ bypass producer.
>
>
> Is there any side effect if it was still registered?

Not much side effect in theory, just some legacy mode IRQs in producer
list and it's not easy to distinguish them with PI interrupt mode IRQ.
The main purpose of this patch is to provide a way for people to know
if a device IRQ is really offloaded from kernel by a print.
>
>
> >
> > With this change, below message is printed:
> > "vfio-pci 0000:db:00.0: irq bypass producer (token 0000000060c8cda5) re=
gistration fails: -22"
>
>
> I may miss something, but the patch only touches vhost-vDPA instead of VF=
IO?

VFIO already has above print in vfio_msi_set_vector_signal() but vhost-vDPA=
 not.

Regards
Zhenzhong