On Fri, Mar 22, 2024 at 3:58 PM Xuan Zhuo [off-list ref] wrote:

On Fri, 22 Mar 2024 13:15:10 +0800, Jason Wang [off-list ref] wrote:

quoted

On Thu, Mar 21, 2024 at 4:29 PM Xuan Zhuo [off-list ref] wrote:

quoted

On Thu, 21 Mar 2024 12:47:18 +0800, Jason Wang [off-list ref] wrote:

quoted

On Tue, Mar 12, 2024 at 11:36 AM Xuan Zhuo [off-list ref] wrote:

quoted

This commit structure the indirect desc table.
Then we can get the desc num directly when doing unmap.

And save the dma info to the struct, then the indirect
will not use the dma fields of the desc_extra. The subsequent
commits will make the dma fields are optional. But for
the indirect case, we must record the dma info.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
 drivers/virtio/virtio_ring.c | 66 +++++++++++++++++++++---------------
 1 file changed, 38 insertions(+), 28 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 0dfbd17e5a87..22a588bba166 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c

@@ -72,9 +72,16 @@ struct vring_desc_state_split {
        struct vring_desc *indir_desc;  /* Indirect descriptor, if any. */
 };

+struct vring_packed_desc_indir {
+       dma_addr_t addr;                /* Descriptor Array DMA addr. */
+       u32 len;                        /* Descriptor Array length. */
+       u32 num;
+       struct vring_packed_desc desc[];
+};
+
 struct vring_desc_state_packed {
        void *data;                     /* Data for callback. */
-       struct vring_packed_desc *indir_desc; /* Indirect descriptor, if any. */
+       struct vring_packed_desc_indir *indir_desc; /* Indirect descriptor, if any. */

Maybe it's better just to have a vring_desc_extra here.

Do you mean replacing vring_packed_desc_indir by vring_desc_extra?

Just add a vring_desc_extra in vring_desc_state_packed.

quoted

I am ok for that. But vring_desc_extra has two extra items:

        u16 flags;                      /* Descriptor flags. */
        u16 next;                       /* The next desc state in a list. */

vring_packed_desc_indir has "desc". I think that is more convenient.

So, I think vring_packed_desc_indir is appropriate.

It reuses the existing structure so we had the chance to reuse the
helper.

Do you mean vring_unmap_extra_packed()?

Yes.

After last commit(virtio_ring: packed: remove double check of the unmap ops):

        /* caller must check vring_need_unmap_buffer() */
        static void vring_unmap_extra_packed(const struct vring_virtqueue *vq,
                                             const struct vring_desc_extra *extra)
        {
                u16 flags;

                flags = extra->flags;

                dma_unmap_page(vring_dma_dev(vq),
                               extra->addr, extra->len,
                               (flags & VRING_DESC_F_WRITE) ?
                               DMA_FROM_DEVICE : DMA_TO_DEVICE);
        }

But we should call dma_unmap_single() for indirect desc.

We know, dma_unmap_single() and dma_unmap_page() are same in essence.

Yes, it's worth tweaking in the future.

So if we call dma_unmap_page for the indirect desc, we can reuse
this function. But I do not prefer doing this.

Ok.

Thanks

Thanks.

quoted

And it could be used for future chained indirect (if it turns
out to be necessary).

Thanks

quoted

Or I missed something.


Thanks.

quoted

Thanks