linux-kernel - Re: [PATCH v2 01/11] genirq/affinity:: Export irq_create_affinity

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Message-ID: <CACycT3u=vULuZ9-ZakBjxmbu88iUb+xB2mHJUnHA_8SuUV7H4w@mail.gmail.com>
Date:   Mon, 30 Jan 2023 19:53:55 +0800
From:   Yongji Xie <xieyongji@...edance.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Christoph Hellwig <hch@....de>, Jason Wang <jasowang@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        virtualization <virtualization@...ts.linux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 01/11] genirq/affinity:: Export irq_create_affinity_masks()

On Fri, Jan 27, 2023 at 4:22 PM Michael S. Tsirkin <mst@...hat.com> wrote:
>
> On Mon, Dec 19, 2022 at 05:36:02PM +0800, Yongji Xie wrote:
> > On Mon, Dec 19, 2022 at 3:33 PM Michael S. Tsirkin <mst@...hat.com> wrote:
> > >
> > > On Mon, Dec 05, 2022 at 04:41:17PM +0800, Xie Yongji wrote:
> > > > Export irq_create_affinity_masks() so that some modules
> > > > can make use of it to implement interrupt affinity
> > > > spreading mechanism.
> > > >
> > > > Signed-off-by: Xie Yongji <xieyongji@...edance.com>
> > >
> > > So this got nacked, what's the plan now?
> > >
> >
> > I‘d like to check with Christoph again first.
> >
> > Hi Christoph,
> >
> > Jason will post some patches to get rid of the DMA API for vDPA
> > simulators. And the irq affinity algorithm is independent of the IRQ
> > subsystem IIUC. So could you allow this patch so that we can reuse the
> > algorithm to select the best CPU (per-cpu affinity if possible, or at
> > least per-node) to run the virtqueue's irq callback.
> >
> > Thanks,
> > Yongji
>
> I think you need to explain why you are building low level
> affinity masks.

In VDUSE case, we use workqueue to run the virtqueue's irq callback.
Now I want to queue the irq callback kwork to one specific CPU to get
per-cpu affinity if possible, or at least per-node. So I need to use
this function to build the low level affinity masks for each
virtqueue.

> what's the plan now?
>

If there is no objection, I'll post a new version.

Thanks,
Yongji