linux-kernel - Re: [PATCH 1/2] virtio_pci: Don't make an extra copy of cpu affinity mask

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Message-ID: <1697720122.49851-2-xuanzhuo@linux.alibaba.com>
Date:   Thu, 19 Oct 2023 20:55:22 +0800
From:   Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To:     Jakub Sitnicki <jakub@...udflare.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>, linux-kernel@...r.kernel.org,
        kernel-team@...udflare.com, Caleb Raitto <caraitto@...gle.com>,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH 1/2] virtio_pci: Don't make an extra copy of cpu affinity mask

On Thu, 19 Oct 2023 12:16:24 +0200, Jakub Sitnicki <jakub@...udflare.com> wrote:
> Since commit 19e226e8cc5d ("virtio: Make vp_set_vq_affinity() take a
> mask.") it is actually not needed to have a local copy of the cpu mask.


Could you give more info to prove this?

If you are right, I think you should delete all code about msix_affinity_masks?

Thanks.

>
> Pass the cpu mask we got as argument to set the irq affinity hint.
>
> Cc: Caleb Raitto <caraitto@...gle.com>
> Signed-off-by: Jakub Sitnicki <jakub@...udflare.com>
> ---
>  drivers/virtio/virtio_pci_common.c | 9 +--------
>  1 file changed, 1 insertion(+), 8 deletions(-)
>
> diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
> index c2524a7207cf..8927bc338f06 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -433,21 +433,14 @@ int vp_set_vq_affinity(struct virtqueue *vq, const struct cpumask *cpu_mask)
>  	struct virtio_device *vdev = vq->vdev;
>  	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
>  	struct virtio_pci_vq_info *info = vp_dev->vqs[vq->index];
> -	struct cpumask *mask;
>  	unsigned int irq;
>
>  	if (!vq->callback)
>  		return -EINVAL;
>
>  	if (vp_dev->msix_enabled) {
> -		mask = vp_dev->msix_affinity_masks[info->msix_vector];
>  		irq = pci_irq_vector(vp_dev->pci_dev, info->msix_vector);
> -		if (!cpu_mask)
> -			irq_set_affinity_hint(irq, NULL);
> -		else {
> -			cpumask_copy(mask, cpu_mask);
> -			irq_set_affinity_hint(irq, mask);
> -		}
> +		irq_set_affinity_hint(irq, cpu_mask);
>  	}
>  	return 0;
>  }
> --
> 2.41.0
>