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-rw-r--r--Documentation/lguest/lguest.c25
1 files changed, 21 insertions, 4 deletions
diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c
index 84bbb190bf7b..ba9373f82ab5 100644
--- a/Documentation/lguest/lguest.c
+++ b/Documentation/lguest/lguest.c
@@ -134,6 +134,9 @@ struct device {
/* Is it operational */
bool running;
+ /* Does Guest want an intrrupt on empty? */
+ bool irq_on_empty;
+
/* Device-specific data. */
void *priv;
};
@@ -624,10 +627,13 @@ static void trigger_irq(struct virtqueue *vq)
return;
vq->pending_used = 0;
- /* If they don't want an interrupt, don't send one, unless empty. */
- if ((vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
- && lg_last_avail(vq) != vq->vring.avail->idx)
- return;
+ /* If they don't want an interrupt, don't send one... */
+ if (vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT) {
+ /* ... unless they've asked us to force one on empty. */
+ if (!vq->dev->irq_on_empty
+ || lg_last_avail(vq) != vq->vring.avail->idx)
+ return;
+ }
/* Send the Guest an interrupt tell them we used something up. */
if (write(lguest_fd, buf, sizeof(buf)) != 0)
@@ -1043,6 +1049,15 @@ static void create_thread(struct virtqueue *vq)
close(vq->eventfd);
}
+static bool accepted_feature(struct device *dev, unsigned int bit)
+{
+ const u8 *features = get_feature_bits(dev) + dev->feature_len;
+
+ if (dev->feature_len < bit / CHAR_BIT)
+ return false;
+ return features[bit / CHAR_BIT] & (1 << (bit % CHAR_BIT));
+}
+
static void start_device(struct device *dev)
{
unsigned int i;
@@ -1056,6 +1071,8 @@ static void start_device(struct device *dev)
verbose(" %02x", get_feature_bits(dev)
[dev->feature_len+i]);
+ dev->irq_on_empty = accepted_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY);
+
for (vq = dev->vq; vq; vq = vq->next) {
if (vq->service)
create_thread(vq);