linux-kernel - Re: [PATCH v2 03/11] vdpa: Add set_irq_affinity callback in vdpa_config

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Message-ID: <CACGkMEvYpBz6wdOPFvRveT=0AO=g-nzaeJt3y99oqWDLHUs=qw@mail.gmail.com>
Date:   Fri, 16 Dec 2022 11:58:15 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Xie Yongji <xieyongji@...edance.com>
Cc:     mst@...hat.com, tglx@...utronix.de, hch@....de,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 03/11] vdpa: Add set_irq_affinity callback in vdpa_config_ops

On Mon, Dec 5, 2022 at 4:43 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         | 8 ++++++++
>  2 files changed, 12 insertions(+)
>
> diff --git a/drivers/virtio/virtio_vdpa.c b/drivers/virtio/virtio_vdpa.c
> index 08084b49e5a1..4731e4616ee0 100644
> --- a/drivers/virtio/virtio_vdpa.c
> +++ b/drivers/virtio/virtio_vdpa.c
> @@ -275,9 +275,13 @@ 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);

I wonder if we need to do this in vhost-vDPA. Or it's better to have a
default affinity by the vDPA parent itself.

(Looking at virtio-pci, it doesn't do something like this).

Thanks

> +
>         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 0ff6c9363356..482ff7d0206f 100644
> --- a/include/linux/vdpa.h
> +++ b/include/linux/vdpa.h
> @@ -256,6 +256,12 @@ struct vdpa_map_file {
>   *                             @vdev: vdpa device
>   *                             @idx: virtqueue index
>   *                             Returns the irq affinity mask
> + * @set_irq_affinity:          Pass the irq affinity hint from the virtio
> + *                             device driver to vdpa driver (optional).
> + *                             Needed by the interrupt affinity spreading
> + *                             mechanism.
> + *                             @vdev: vdpa device
> + *                             @desc: irq affinity hint
>   * @set_group_asid:            Set address space identifier for a
>   *                             virtqueue group (optional)
>   *                             @vdev: vdpa device
> @@ -344,6 +350,8 @@ struct vdpa_config_ops {
>                                const struct cpumask *cpu_mask);
>         const struct cpumask *(*get_vq_affinity)(struct vdpa_device *vdev,
>                                                  u16 idx);
> +       void (*set_irq_affinity)(struct vdpa_device *vdev,
> +                                struct irq_affinity *desc);
>
>         /* DMA ops */
>         int (*set_map)(struct vdpa_device *vdev, unsigned int asid,
> --
> 2.20.1
>