On Tue, Aug 20, 2024 at 3:33 PM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote:
>
> 1. this commit hardens dma unmap for indirect
I think we need to explain why we need such hardening. For example
indirect use stream mapping which is read-only from the device. So it
looks to me like it doesn't require hardening by itself.
> 2. the subsequent commit uses the struct extra to record whether the
> buffers need to be unmapped or not.
It's better to explain why such a decision could not be implied with
the existing metadata.
> So we need a struct extra for
> every desc, whatever it is indirect or not.
If this is the real reason, we need to tweak the title.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
> ---
> drivers/virtio/virtio_ring.c | 122 ++++++++++++++++-------------------
> 1 file changed, 57 insertions(+), 65 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 228e9fbcba3f..582d2c05498a 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -67,9 +67,16 @@
> #define LAST_ADD_TIME_INVALID(vq)
> #endif
>
> +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_state_split {
> void *data; /* Data for callback. */
> - struct vring_desc *indir_desc; /* Indirect descriptor, if any. */
> + struct vring_desc_extra *indir; /* Indirect descriptor, if any. */
Btw, it might be worth explaining that this will be allocated with an
indirect descriptor table so we won't stress more to the memory
allocator.
Thanks
