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authorAmit Shah <amit.shah@redhat.com>2010-11-23 17:01:15 +0530
committerMichael S. Tsirkin <mst@redhat.com>2011-01-12 17:55:30 +0200
commita01a9cb821a29852abb142ec52b26c8488ced6e8 (patch)
treed8214953bd37f5b715e6977e0753c3b3f7721f7f
parentc2e08bddcd1fa32415c0ee5aa6d3c88a258db4c0 (diff)
virtio-serial-bus: bump up control vq size to 32
The current default of 16 buffers for the control vq is too small. We can get more entries in there, for example when asking the guest to add max. allowed ports. Note: a more robust solution would involve some kind of event queueing in host to guarantee no event loss. Added a TODO to look into this later. Signed-off-by: Amit Shah <amit.shah@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
-rw-r--r--hw/virtio-serial-bus.c10
1 files changed, 8 insertions, 2 deletions
diff --git a/hw/virtio-serial-bus.c b/hw/virtio-serial-bus.c
index 74ba5ec3d3..b728040f3a 100644
--- a/hw/virtio-serial-bus.c
+++ b/hw/virtio-serial-bus.c
@@ -769,10 +769,16 @@ VirtIODevice *virtio_serial_init(DeviceState *dev, uint32_t max_nr_ports)
/* Add a queue for guest to host transfers for port 0 (backward compat) */
vser->ovqs[0] = virtio_add_queue(vdev, 128, handle_output);
+ /* TODO: host to guest notifications can get dropped
+ * if the queue fills up. Implement queueing in host,
+ * this might also make it possible to reduce the control
+ * queue size: as guest preposts buffers there,
+ * this will save 4Kbyte of guest memory per entry. */
+
/* control queue: host to guest */
- vser->c_ivq = virtio_add_queue(vdev, 16, control_in);
+ vser->c_ivq = virtio_add_queue(vdev, 32, control_in);
/* control queue: guest to host */
- vser->c_ovq = virtio_add_queue(vdev, 16, control_out);
+ vser->c_ovq = virtio_add_queue(vdev, 32, control_out);
for (i = 1; i < vser->bus->max_nr_ports; i++) {
/* Add a per-port queue for host to guest transfers */