linux-kernel - Re: [PATCH v3 03/11] vdpa: Add set_irq_affinity callback in vdpa_config

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Date:   Mon, 20 Mar 2023 17:31:29 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Yongji Xie <xieyongji@...edance.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Christoph Hellwig <hch@....de>,
        virtualization <virtualization@...ts.linux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 03/11] vdpa: Add set_irq_affinity callback in vdpa_config_ops

On Fri, Mar 17, 2023 at 3:45 PM Yongji Xie <xieyongji@...edance.com> wrote:
>
> On Thu, Mar 16, 2023 at 12:03 PM Jason Wang <jasowang@...hat.com> wrote:
> >
> > On Tue, Feb 28, 2023 at 5:42 PM Xie Yongji <xieyongji@...edance.com> wrote:
> > >
> > > This introduces set_irq_affinity callback in
> > > vdpa_config_ops so that vdpa device driver can
> > > get the interrupt affinity hint from the virtio
> > > device driver. The interrupt affinity hint would
> > > be needed by the interrupt affinity spreading
> > > mechanism.
> > >
> > > Signed-off-by: Xie Yongji <xieyongji@...edance.com>
> > > ---
> > >  drivers/virtio/virtio_vdpa.c | 4 ++++
> > >  include/linux/vdpa.h         | 9 +++++++++
> > >  2 files changed, 13 insertions(+)
> > >
> > > diff --git a/drivers/virtio/virtio_vdpa.c b/drivers/virtio/virtio_vdpa.c
> > > index f72696b4c1c2..9eee8afabda8 100644
> > > --- a/drivers/virtio/virtio_vdpa.c
> > > +++ b/drivers/virtio/virtio_vdpa.c
> > > @@ -282,9 +282,13 @@ static int virtio_vdpa_find_vqs(struct virtio_device *vdev, unsigned int nvqs,
> > >         struct virtio_vdpa_device *vd_dev = to_virtio_vdpa_device(vdev);
> > >         struct vdpa_device *vdpa = vd_get_vdpa(vdev);
> > >         const struct vdpa_config_ops *ops = vdpa->config;
> > > +       struct irq_affinity default_affd = { 0 };
> > >         struct vdpa_callback cb;
> > >         int i, err, queue_idx = 0;
> > >
> > > +       if (ops->set_irq_affinity)
> > > +               ops->set_irq_affinity(vdpa, desc ? desc : &default_affd);
> > > +
> > >         for (i = 0; i < nvqs; ++i) {
> > >                 if (!names[i]) {
> > >                         vqs[i] = NULL;
> > > diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
> > > index d61f369f9cd6..10bd22387276 100644
> > > --- a/include/linux/vdpa.h
> > > +++ b/include/linux/vdpa.h
> > > @@ -259,6 +259,13 @@ struct vdpa_map_file {
> > >   *                             @vdev: vdpa device
> > >   *                             @idx: virtqueue index
> > >   *                             Returns the irq affinity mask
> > > + * @set_irq_affinity:          Pass the irq affinity hint (best effort)
> >
> > Note that this could easily confuse the users. I wonder if we can
> > unify it with set_irq_affinity. Looking at vduse's implementation, it
> > should be possible.
> >
>
> Do you mean unify set_irq_affinity() with set_vq_affinity()? Actually
> I didn't get how to achieve that. The set_vq_affinity() callback is
> called by virtio_config_ops.set_vq_affinity() but the set_irq_affinity
> is called by virtio_config_ops.find_vqs(), I don't know where to call
> the unified callback.

I meant, can we stick a single per vq affinity config ops then use
that in virtio-vpda's find_vqs() by something like:

masks = create_affinity_masks(dev->vq_num, desc);
for (i = 0; i < dev->vq_num; i++)
        config->set_vq_affinity()
...

?

Thanks

>
> Thanks,
> Yongji
>