在 2022/8/17 21:57, Guo Zhi 写道:
Follow VIRTIO 1.1 spec, only writing out a single used ring for a batch
of descriptors.
Signed-off-by: Guo Zhi <qtxuning1999@xxxxxxxxxxx>
---
drivers/vhost/vhost.c | 14 ++++++++++++--
drivers/vhost/vhost.h | 1 +
2 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 40097826cff0..7b20fa5a46c3 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -2376,10 +2376,20 @@ static int __vhost_add_used_n(struct vhost_virtqueue *vq,
vring_used_elem_t __user *used;
u16 old, new;
int start;
+ int copy_n = count;
+ /**
+ * If in order feature negotiated, devices can notify the use of a batch of buffers to
+ * the driver by only writing out a single used ring entry with the id corresponding
+ * to the head entry of the descriptor chain describing the last buffer in the batch.
+ */
+ if (vhost_has_feature(vq, VIRTIO_F_IN_ORDER)) {
+ copy_n = 1;
+ heads = &heads[count - 1];
Do we need to check whether or not the buffer is fully used before doing
this?
+ }
start = vq->last_used_idx & (vq->num - 1);
used = vq->used->ring + start;
- if (vhost_put_used(vq, heads, start, count)) {
+ if (vhost_put_used(vq, heads, start, copy_n)) {
vq_err(vq, "Failed to write used");
return -EFAULT;
}
@@ -2410,7 +2420,7 @@ int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
start = vq->last_used_idx & (vq->num - 1);
n = vq->num - start;
- if (n < count) {
+ if (n < count && !vhost_has_feature(vq, VIRTIO_F_IN_ORDER)) {
r = __vhost_add_used_n(vq, heads, n);
if (r < 0)
return r;
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index d9109107af08..0d5c49a30421 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -236,6 +236,7 @@ enum {
VHOST_FEATURES = (1ULL << VIRTIO_F_NOTIFY_ON_EMPTY) |
(1ULL << VIRTIO_RING_F_INDIRECT_DESC) |
(1ULL << VIRTIO_RING_F_EVENT_IDX) |
+ (1ULL << VIRTIO_F_IN_ORDER) |
(1ULL << VHOST_F_LOG_ALL) |
Are we sure all vhost devices can support in-order (especially the SCSI)?
It looks better to start from a device specific one.
Thanks
(1ULL << VIRTIO_F_ANY_LAYOUT) |
(1ULL << VIRTIO_F_VERSION_1)
