On Wed, Mar 27, 2024 at 3:16 PM Xuan Zhuo [off-list ref] wrote:

On Tue, 26 Mar 2024 14:35:21 +0800, Jason Wang [off-list ref] wrote:

quoted

On Mon, Mar 25, 2024 at 4:54 PM Xuan Zhuo [off-list ref] wrote:

quoted

As discussed:

http://lore.kernel.org/all/CACGkMEvq0No8QGC46U4mGsMtuD44fD_cfLcPaVmJ3rHYqRZxYg@mail.gmail.com (local)

If the virtio is premapped mode, the driver should manage the dma info by self.
So the virtio core should not store the dma info. We can release the memory used
to store the dma info.

For virtio-net xmit queue, if the virtio-net maintains the dma info,
the virtio-net must allocate too much memory(19 * queue_size for per-queue), so
we do not plan to make the virtio-net to maintain the dma info by default. The
virtio-net xmit queue only maintain the dma info when premapped mode is enable
(such as AF_XDP is enable).

So this patch set try to do:

1. make the virtio core to do not store the dma info when driver can do that
    - But if the desc_extra has not dma info, we face a new question,
      it is hard to get the dma info of the desc with indirect flag.
      For split mode, that is easy from desc, but for the packed mode,
      it is hard to get the dma info from the desc. And hardening
      the dma unmap is safe, we should store the dma info of indirect
      descs when the virtio core does not store the bufer dma info.

      The follow patches to this:
         * virtio_ring: packed: structure the indirect desc table
         * virtio_ring: split: structure the indirect desc table

    - On the other side, in the umap handle, we mix the indirect descs with
      other descs. That make things too complex. I found if we we distinguish
      the descs with VRING_DESC_F_INDIRECT before unmap, thing will be clearer.

      The follow patches do this.
         * virtio_ring: packed: remove double check of the unmap ops
         * virtio_ring: split: structure the indirect desc table

2. make the virtio core to enable premapped mode by find_vqs() params
    - Because the find_vqs() will try to allocate memory for the dma info.
      If we set the premapped mode after find_vqs() and release the
      dma info, that is odd.


Please review.

Thanks

This doesn't apply cleany on vhost.git linux-next branch.

Which tree is this based on?

Sorry. That is on the top of "[PATCH vhost v5 0/6] refactor the params of
find_vqs()".

Lore-URL: http://lore.kernel.org/all/20240325090419.33677-1-xuanzhuo@linux.alibaba.com (local)

Thanks.

I've tried that but it doesn't work:

% git am ~/Downloads/\[PATCH\ vhost\ v5\ 01_10\]\ virtio_ring_\
introduce\ vring_need_unmap_buffer.eml
Applying: virtio_ring: introduce vring_need_unmap_buffer
error: patch failed: drivers/virtio/virtio_ring.c:2080
error: drivers/virtio/virtio_ring.c: patch does not apply
Patch failed at 0001 virtio_ring: introduce vring_need_unmap_buffer
hint: Use 'git am --show-current-patch=diff' to see the failed patch
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

I'm using vhost.git linux-next branch, HEAD is

commit 56e71885b0349241c07631a7b979b61e81afab6a
Author: Maxime Coquelin [off-list ref]
Date:   Tue Jan 9 12:10:24 2024 +0100

    vduse: Temporarily fail if control queue feature requested

Thanks

quoted

Thanks