[Qemu-devel] [PATCH 1/3] virtio: introduce virtqueue_unmap_sg()

[Qemu-devel] [PATCH 1/3] virtio: introduce virtqueue_unmap_sg()

[Jason Wang]

Factor out sg unmapping logic. This will be reused by the patch that
can discard descriptor.

Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 hw/virtio/virtio.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 0832db9..eb8d5ca 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -243,15 +243,12 @@ int virtio_queue_empty(VirtQueue *vq)
     return vring_avail_idx(vq) == vq->last_avail_idx;
 }
 
-void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
-                    unsigned int len, unsigned int idx)
+static void virtqueue_unmap_sg(VirtQueue *vq, const VirtQueueElement *elem,
+                               unsigned int len)
 {
     unsigned int offset;
     int i;
 
-    trace_virtqueue_fill(vq, elem, len, idx);
-
-    offset = 0;
     for (i = 0; i < elem->in_num; i++) {
         size_t size = MIN(len - offset, elem->in_sg[i].iov_len);
 
@@ -266,6 +263,14 @@ void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
         cpu_physical_memory_unmap(elem->out_sg[i].iov_base,
                                   elem->out_sg[i].iov_len,
                                   0, elem->out_sg[i].iov_len);
+}
+
+void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
+                    unsigned int len, unsigned int idx)
+{
+    trace_virtqueue_fill(vq, elem, len, idx);
+
+    virtqueue_unmap_sg(vq, elem, len);
 
     idx = (idx + vring_used_idx(vq)) % vq->vring.num;
 
-- 
2.1.4

[Qemu-devel] [PATCH 2/3] virtio: introduce virtqueue_discard()

[Jason Wang]

This patch introduces virtqueue_discard() to discard a descriptor and
unmap the sgs. This will be used by the patch that will discard
descriptor when packet is truncated.

Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 hw/virtio/virtio.c         | 7 +++++++
 include/hw/virtio/virtio.h | 2 ++
 2 files changed, 9 insertions(+)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index eb8d5ca..d24ee80 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -265,6 +265,13 @@ static void virtqueue_unmap_sg(VirtQueue *vq, const VirtQueueElement *elem,
                                   0, elem->out_sg[i].iov_len);
 }
 
+void virtqueue_discard(VirtQueue *vq, const VirtQueueElement *elem,
+                       unsigned int len)
+{
+    vq->last_avail_idx--;
+    virtqueue_unmap_sg(vq, elem, len);
+}
+
 void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
                     unsigned int len, unsigned int idx)
 {
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 6201ee8..9d09115 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -146,6 +146,8 @@ void virtio_del_queue(VirtIODevice *vdev, int n);
 void virtqueue_push(VirtQueue *vq, const VirtQueueElement *elem,
                     unsigned int len);
 void virtqueue_flush(VirtQueue *vq, unsigned int count);
+void virtqueue_discard(VirtQueue *vq, const VirtQueueElement *elem,
+                       unsigned int len);
 void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
                     unsigned int len, unsigned int idx);
 
-- 
2.1.4

[Qemu-devel] [PATCH 3/3] virtio-net: correctly drop truncated packets

[Jason Wang]

When packet is truncated during receiving, we drop the packets but
neither discard the descriptor nor add and signal used
descriptor. This will lead several issues:

- sg mappings are leaked
- rx will be stalled if a lots of packets were truncated

In order to be consistent with vhost, fix by discarding the descriptor
in this case.

Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 hw/net/virtio-net.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index f72eebf..038a18b 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1086,13 +1086,7 @@ static ssize_t virtio_net_receive(NetClientState *nc, const uint8_t *buf, size_t
          * must have consumed the complete packet.
          * Otherwise, drop it. */
         if (!n->mergeable_rx_bufs && offset < size) {
-#if 0
-            error_report("virtio-net truncated non-mergeable packet: "
-                         "i %zd mergeable %d offset %zd, size %zd, "
-                         "guest hdr len %zd, host hdr len %zd",
-                         i, n->mergeable_rx_bufs,
-                         offset, size, n->guest_hdr_len, n->host_hdr_len);
-#endif
+            virtqueue_discard(q->rx_vq, &elem, total);
             return size;
         }
 
-- 
2.1.4

Re: [Qemu-devel] [PATCH 1/3] virtio: introduce virtqueue_unmap_sg()

[Andrew James]

On 09/18/2015 02:01 AM, Jason Wang wrote:
> Factor out sg unmapping logic. This will be reused by the patch that
> can discard descriptor.
> 
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
>  hw/virtio/virtio.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 0832db9..eb8d5ca 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -243,15 +243,12 @@ int virtio_queue_empty(VirtQueue *vq)
>      return vring_avail_idx(vq) == vq->last_avail_idx;
>  }
>  
> -void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
> -                    unsigned int len, unsigned int idx)
> +static void virtqueue_unmap_sg(VirtQueue *vq, const VirtQueueElement *elem,
> +                               unsigned int len)
>  {
>      unsigned int offset;
>      int i;
>  
> -    trace_virtqueue_fill(vq, elem, len, idx);
> -
> -    offset = 0;
>      for (i = 0; i < elem->in_num; i++) {
>          size_t size = MIN(len - offset, elem->in_sg[i].iov_len);
>  

Should the "offset = 0" really be dropped here? Seems like it ends
up uninitialized. GCC thinks it might too.

> @@ -266,6 +263,14 @@ void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
>          cpu_physical_memory_unmap(elem->out_sg[i].iov_base,
>                                    elem->out_sg[i].iov_len,
>                                    0, elem->out_sg[i].iov_len);
> +}
> +
> +void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
> +                    unsigned int len, unsigned int idx)
> +{
> +    trace_virtqueue_fill(vq, elem, len, idx);
> +
> +    virtqueue_unmap_sg(vq, elem, len);
>  
>      idx = (idx + vring_used_idx(vq)) % vq->vring.num;
>  
> 

Thanks,
-- 
Andrew James

Re: [Qemu-devel] [PATCH 1/3] virtio: introduce virtqueue_unmap_sg()

[Andrew James]

On 09/18/2015 02:01 AM, Jason Wang wrote:
> Factor out sg unmapping logic. This will be reused by the patch that
> can discard descriptor.
> 
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
>  hw/virtio/virtio.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 0832db9..eb8d5ca 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -243,15 +243,12 @@ int virtio_queue_empty(VirtQueue *vq)
>      return vring_avail_idx(vq) == vq->last_avail_idx;
>  }
>  
> -void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
> -                    unsigned int len, unsigned int idx)
> +static void virtqueue_unmap_sg(VirtQueue *vq, const VirtQueueElement *elem,
> +                               unsigned int len)
>  {
>      unsigned int offset;
>      int i;
>  
> -    trace_virtqueue_fill(vq, elem, len, idx);
> -
> -    offset = 0;
>      for (i = 0; i < elem->in_num; i++) {
>          size_t size = MIN(len - offset, elem->in_sg[i].iov_len);
>  

Should the "offset = 0" really be dropped here? Seems like it ends
up uninitialized. GCC thinks it might too.

> @@ -266,6 +263,14 @@ void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
>          cpu_physical_memory_unmap(elem->out_sg[i].iov_base,
>                                    elem->out_sg[i].iov_len,
>                                    0, elem->out_sg[i].iov_len);
> +}
> +
> +void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
> +                    unsigned int len, unsigned int idx)
> +{
> +    trace_virtqueue_fill(vq, elem, len, idx);
> +
> +    virtqueue_unmap_sg(vq, elem, len);
>  
>      idx = (idx + vring_used_idx(vq)) % vq->vring.num;
>  
> 

Thanks,
-- 
Andrew James

Re: [Qemu-devel] [PATCH 1/3] virtio: introduce virtqueue_unmap_sg()

[Jason Wang]

On 09/25/2015 12:19 AM, Andrew James wrote:
> On 09/18/2015 02:01 AM, Jason Wang wrote:
>> > Factor out sg unmapping logic. This will be reused by the patch that
>> > can discard descriptor.
>> > 
>> > Cc: Michael S. Tsirkin <mst@redhat.com>
>> > Signed-off-by: Jason Wang <jasowang@redhat.com>
>> > ---
>> >  hw/virtio/virtio.c | 15 ++++++++++-----
>> >  1 file changed, 10 insertions(+), 5 deletions(-)
>> > 
>> > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
>> > index 0832db9..eb8d5ca 100644
>> > --- a/hw/virtio/virtio.c
>> > +++ b/hw/virtio/virtio.c
>> > @@ -243,15 +243,12 @@ int virtio_queue_empty(VirtQueue *vq)
>> >      return vring_avail_idx(vq) == vq->last_avail_idx;
>> >  }
>> >  
>> > -void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
>> > -                    unsigned int len, unsigned int idx)
>> > +static void virtqueue_unmap_sg(VirtQueue *vq, const VirtQueueElement *elem,
>> > +                               unsigned int len)
>> >  {
>> >      unsigned int offset;
>> >      int i;
>> >  
>> > -    trace_virtqueue_fill(vq, elem, len, idx);
>> > -
>> > -    offset = 0;
>> >      for (i = 0; i < elem->in_num; i++) {
>> >          size_t size = MIN(len - offset, elem->in_sg[i].iov_len);
>> >  
> Should the "offset = 0" really be dropped here? 

Probably not.

> Seems like it ends
> up uninitialized. GCC thinks it might too.
>

Yes, will keep the offset initialization in V2.

Thanks