On Fri, Mar 22, 2024 at 3:58 PM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote:
>
> On Fri, 22 Mar 2024 13:15:10 +0800, Jason Wang <jasowang@xxxxxxxxxx> wrote:
> > On Thu, Mar 21, 2024 at 4:29 PM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote:
> > >
> > > On Thu, 21 Mar 2024 12:47:18 +0800, Jason Wang <jasowang@xxxxxxxxxx> wrote:
> > > > On Tue, Mar 12, 2024 at 11:36 AM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote:
> > > > >
> > > > > 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@xxxxxxxxxxxxxxxxx>
> > > > > ---
> > > > > 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.
> >
> > >
> > > 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.
>
>
> > And it could be used for future chained indirect (if it turns
> > out to be necessary).
> >
> > Thanks
> >
> > > Or I missed something.
> > >
> > >
> > > Thanks.
> > >
> > >
> > > >
> > > > Thanks
> > > >
> > >
> >
> >
>
