[PATCH net-next 5/8] vhost: track zero copy failures using DMA length

Michael S. Tsirkin
2012-10-29T15:56:03Z

This will be used to disable zerocopy when error rate
is high.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
drivers/vhost/vhost.c | 7 ++++---
drivers/vhost/vhost.h | 4 ++++
2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 906fd9f..5affce3 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -425,7 +425,7 @@ int vhost_zerocopy_signal_used(struct vhost_virtqueue *vq)
int j = 0;

for (i = vq->done_idx; i != vq->upend_idx; i = (i + 1) % UIO_MAXIOV) {
- if ((vq->heads[i].len == VHOST_DMA_DONE_LEN)) {
+ if (VHOST_DMA_IS_DONE(vq->heads[i].len)) {
vq->heads[i].len = VHOST_DMA_CLEAR_LEN;
vhost_add_used_and_signal(vq->dev, vq,
vq->heads[i].id, 0);
@@ -1600,13 +1600,14 @@ void vhost_ubuf_put_and_wait(struct vhost_ubuf_ref *ubufs)
kfree(ubufs);
}

-void vhost_zerocopy_callback(struct ubuf_info *ubuf, int zerocopy_status)
+void vhost_zerocopy_callback(struct ubuf_info *ubuf, int status)
{
struct vhost_ubuf_ref *ubufs = ubuf->ctx;
struct vhost_virtqueue *vq = ubufs->vq;

vhost_poll_queue(&vq->poll);
/* set len to mark this desc buffers done DMA */
- vq->heads[ubuf->desc].len = VHOST_DMA_DONE_LEN;
+ vq->heads[ubuf->desc].len = status ?
+ VHOST_DMA_FAILED_LEN : VHOST_DMA_DONE_LEN;
kref_put(&ubufs->kref, vhost_zerocopy_done_signal);
}
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index ad72a1f..6fdf31d 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -17,6 +17,8 @@
* For transmit, used buffer len is unused; we override it to track buffer
* status internally; used for zerocopy tx only.
*/
+/* Lower device DMA failed */
+#define VHOST_DMA_FAILED_LEN 3
/* Lower device DMA done */
#define VHOST_DMA_DONE_LEN 2
/* Lower device DMA in progress */
@@ -24,6 +26,8 @@
/* Buffer unused */
#define VHOST_DMA_CLEAR_LEN 0

+#define VHOST_DMA_IS_DONE(len) ((len) >= VHOST_DMA_DONE_LEN)
+
struct vhost_device;

struct vhost_work;
--
MST