linux-kernel - Re: [PATCH v3 2/2] powerpc/pseries: pass MSI affinity to irq_create

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Date:   Wed, 25 Nov 2020 18:34:12 +0100
From:   Greg Kurz <groug@...d.org>
To:     Marc Zyngier <maz@...nel.org>
CC:     Laurent Vivier <lvivier@...hat.com>,
        Denis Kirjanov <kda@...ux-powerpc.org>,
        <linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        Christoph Hellwig <hch@....de>,
        Paul Mackerras <paulus@...ba.org>,
        <linuxppc-dev@...ts.ozlabs.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        <linux-block@...r.kernel.org>,
        "Michael S . Tsirkin" <mst@...hat.com>
Subject: Re: [PATCH v3 2/2] powerpc/pseries: pass MSI affinity to
 irq_create_mapping()

On Wed, 25 Nov 2020 16:42:30 +0000
Marc Zyngier <maz@...nel.org> wrote:

> On 2020-11-25 16:24, Laurent Vivier wrote:
> > On 25/11/2020 17:05, Denis Kirjanov wrote:
> >> On 11/25/20, Laurent Vivier <lvivier@...hat.com> wrote:
> >>> With virtio multiqueue, normally each queue IRQ is mapped to a CPU.
> >>> 
> >>> But since commit 0d9f0a52c8b9f ("virtio_scsi: use virtio IRQ 
> >>> affinity")
> >>> this is broken on pseries.
> >> 
> >> Please add "Fixes" tag.
> > 
> > In fact, the code in commit 0d9f0a52c8b9f is correct.
> > 
> > The problem is with MSI/X irq affinity and pseries. So this patch
> > fixes more than virtio_scsi. I put this information because this
> > commit allows to clearly show the problem. Perhaps I should remove
> > this line in fact?
> 
> This patch does not fix virtio_scsi at all, which as you noticed, is
> correct. It really fixes the PPC MSI setup, which is starting to show
> its age. So getting rid of the reference seems like the right thing to 
> do.
> 
> I'm also not keen on the BugId thing. It should really be a lore link.
> I also cannot find any such tag in the kernel, nor is it a documented
> practice. The last reference to a Bugzilla entry seems to have happened
> with 786b5219081ff16 (five years ago).
> 

My bad, I suggested BugId to Laurent but the intent was actually BugLink,
which seems to be commonly used in the kernel.

Cheers,

--
Greg

> Thanks,
> 
>          M.