Patchwork [9/9] virtio-serial: Handle scatter/gather input from the guest

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Submitter Amit Shah
Date March 23, 2010, 2:30 p.m.
Message ID <1269354619-10201-10-git-send-email-amit.shah@redhat.com>
Download mbox | patch
Permalink /patch/48351/
State New
Headers show

Comments

Amit Shah - March 23, 2010, 2:30 p.m.
Current guests don't send more than one iov but it can change later.
Ensure we handle that case.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
CC: Avi Kivity <avi@redhat.com>
---
 hw/virtio-serial-bus.c |   22 +++++++++++++++-------
 1 files changed, 15 insertions(+), 7 deletions(-)
Amit Shah - March 23, 2010, 3:49 p.m.
On (Tue) Mar 23 2010 [20:00:19], Amit Shah wrote:
> @@ -369,16 +370,23 @@ static void handle_output(VirtIODevice *vdev, VirtQueue *vq)
>           * with it. Just ignore the data in that case.
>           */
>          if (!port->info->have_data) {
> -            ret = 0;
>              goto next_buf;
>          }
>  
> -        /* The guest always sends only one sg */
> -        ret = port->info->have_data(port, elem.out_sg[0].iov_base,
> -                                    elem.out_sg[0].iov_len);
> +        for (i = 0; i < elem.out_num; i++) {
> +            size_t ret;
> +
> +            ret = port->info->have_data(port, elem.out_sg[0].iov_base,
> +                                        elem.out_sg[0].iov_len);
> +            if (ret < elem.out_sg[0].iov_len) {
> +                /* We couldn't write the entire iov; stop processing now */
> +                break;

We should increment len here if ret > 0.

I'll post a followup patch that does this.

> +            }
> +            len += ret;
> +        }
>  
>      next_buf:
> -        virtqueue_push(vq, &elem, ret);
> +        virtqueue_push(vq, &elem, len);
>      }
>      virtio_notify(vdev, vq);
>  }
> -- 
> 1.6.2.5
> 

		Amit

Patch

diff --git a/hw/virtio-serial-bus.c b/hw/virtio-serial-bus.c
index fe976ec..2ca3c0a 100644
--- a/hw/virtio-serial-bus.c
+++ b/hw/virtio-serial-bus.c
@@ -355,11 +355,12 @@  static void handle_output(VirtIODevice *vdev, VirtQueue *vq)
 
     while (virtqueue_pop(vq, &elem)) {
         VirtIOSerialPort *port;
-        size_t ret;
+        size_t len;
+        unsigned int i;
 
+        len = 0;
         port = find_port_by_vq(vser, vq);
         if (!port) {
-            ret = 0;
             goto next_buf;
         }
 
@@ -369,16 +370,23 @@  static void handle_output(VirtIODevice *vdev, VirtQueue *vq)
          * with it. Just ignore the data in that case.
          */
         if (!port->info->have_data) {
-            ret = 0;
             goto next_buf;
         }
 
-        /* The guest always sends only one sg */
-        ret = port->info->have_data(port, elem.out_sg[0].iov_base,
-                                    elem.out_sg[0].iov_len);
+        for (i = 0; i < elem.out_num; i++) {
+            size_t ret;
+
+            ret = port->info->have_data(port, elem.out_sg[0].iov_base,
+                                        elem.out_sg[0].iov_len);
+            if (ret < elem.out_sg[0].iov_len) {
+                /* We couldn't write the entire iov; stop processing now */
+                break;
+            }
+            len += ret;
+        }
 
     next_buf:
-        virtqueue_push(vq, &elem, ret);
+        virtqueue_push(vq, &elem, len);
     }
     virtio_notify(vdev, vq);
 }