netdev - Re: [PATCH vhost v6 06/10] virtio_ring: no store dma info when unmap is not needed

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Message-ID: <CACGkMEsmnzEUmaffn3ueY1JtbJ4UzLpr9o0s4j1jwoVuO-yy8Q@mail.gmail.com>
Date: Thu, 28 Mar 2024 15:06:33 +0800
From: Jason Wang <jasowang@...hat.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc: virtualization@...ts.linux.dev, "Michael S. Tsirkin" <mst@...hat.com>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org
Subject: Re: [PATCH vhost v6 06/10] virtio_ring: no store dma info when unmap
 is not needed

On Wed, Mar 27, 2024 at 7:14 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
>
> As discussed:
> http://lore.kernel.org/all/CACGkMEug-=C+VQhkMYSgUKMC==04m7-uem_yC21bgGkKZh845w@mail.gmail.com
>
> When the vq is premapped mode, the driver manages the dma
> info is a good way.
>
> So this commit make the virtio core not to store the dma
> info and release the memory which is used to store the dma
> info.
>
> If the use_dma_api is false, the memory is also not allocated.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> ---
>  drivers/virtio/virtio_ring.c | 120 ++++++++++++++++++++++++++++-------
>  1 file changed, 97 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 1f7c96543d58..08e4f6e1d722 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -69,23 +69,26 @@
>
>  struct vring_desc_state_split {
>         void *data;                     /* Data for callback. */
> -       struct vring_desc_extra *indir_desc;    /* Indirect descriptor, if any. */
> +       struct vring_desc_dma *indir_desc;      /* Indirect descriptor, if any. */
>  };
>
>  struct vring_desc_state_packed {
>         void *data;                     /* Data for callback. */
> -       struct vring_desc_extra *indir_desc; /* Indirect descriptor, if any. */
> +       struct vring_desc_dma *indir_desc; /* Indirect descriptor, if any. */
>         u16 num;                        /* Descriptor list length. */
>         u16 last;                       /* The last desc state in a list. */
>  };
>
>  struct vring_desc_extra {
> -       dma_addr_t addr;                /* Descriptor DMA addr. */
> -       u32 len;                        /* Descriptor length. */
>         u16 flags;                      /* Descriptor flags. */
>         u16 next;                       /* The next desc state in a list. */
>  };
>
> +struct vring_desc_dma {
> +       dma_addr_t addr;                /* Descriptor DMA addr. */
> +       u32 len;                        /* Descriptor length. */

This seems to be odd, flag should be part of dma info.

To reduce the changeset, I would split out next.

Thank