[RFC PATCH 1/7] virtio-ring: maintain next in extra state for packed virtqueue

From: Jason Wang
Date: Tue Apr 20 2021 - 23:22:06 EST


This patch moves next from vring_desc_state_packed to
vring_desc_desc_extra_packed. This makes it simpler to let extra state
to be reused by split virtqueue.

Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
---
drivers/virtio/virtio_ring.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 71e16b53e9c1..e1e9ed42e637 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -74,7 +74,6 @@ struct vring_desc_state_packed {
void *data; /* Data for callback. */
struct vring_packed_desc *indir_desc; /* Indirect descriptor, if any. */
u16 num; /* Descriptor list length. */
- u16 next; /* The next desc state in a list. */
u16 last; /* The last desc state in a list. */
};

@@ -82,6 +81,7 @@ struct vring_desc_extra_packed {
dma_addr_t addr; /* Buffer DMA addr. */
u32 len; /* Buffer length. */
u16 flags; /* Descriptor flags. */
+ u16 next; /* The next desc state in a list. */
};

struct vring_virtqueue {
@@ -1061,7 +1061,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
1 << VRING_PACKED_DESC_F_USED;
}
vq->packed.next_avail_idx = n;
- vq->free_head = vq->packed.desc_state[id].next;
+ vq->free_head = vq->packed.desc_extra[id].next;

/* Store token and indirect buffer state. */
vq->packed.desc_state[id].num = 1;
@@ -1169,7 +1169,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
le16_to_cpu(flags);
}
prev = curr;
- curr = vq->packed.desc_state[curr].next;
+ curr = vq->packed.desc_extra[curr].next;

if ((unlikely(++i >= vq->packed.vring.num))) {
i = 0;
@@ -1290,7 +1290,7 @@ static void detach_buf_packed(struct vring_virtqueue *vq,
/* Clear data ptr. */
state->data = NULL;

- vq->packed.desc_state[state->last].next = vq->free_head;
+ vq->packed.desc_extra[state->last].next = vq->free_head;
vq->free_head = id;
vq->vq.num_free += state->num;

@@ -1299,7 +1299,7 @@ static void detach_buf_packed(struct vring_virtqueue *vq,
for (i = 0; i < state->num; i++) {
vring_unmap_state_packed(vq,
&vq->packed.desc_extra[curr]);
- curr = vq->packed.desc_state[curr].next;
+ curr = vq->packed.desc_extra[curr].next;
}
}

@@ -1649,8 +1649,6 @@ static struct virtqueue *vring_create_virtqueue_packed(

/* Put everything in free lists. */
vq->free_head = 0;
- for (i = 0; i < num-1; i++)
- vq->packed.desc_state[i].next = i + 1;

vq->packed.desc_extra = kmalloc_array(num,
sizeof(struct vring_desc_extra_packed),
@@ -1661,6 +1659,9 @@ static struct virtqueue *vring_create_virtqueue_packed(
memset(vq->packed.desc_extra, 0,
num * sizeof(struct vring_desc_extra_packed));

+ for (i = 0; i < num - 1; i++)
+ vq->packed.desc_extra[i].next = i + 1;
+
/* No callback? Tell other side not to bother us. */
if (!callback) {
vq->packed.event_flags_shadow = VRING_PACKED_EVENT_FLAG_DISABLE;
--
2.25.1