lguest: notify on empty
This is the lguest implementation of the VIRTIO_F_NOTIFY_ON_EMPTY feature.
It is currently only published for network devices, but it is turned on for
everyone.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c
index 3be8ab2..82fafe0 100644
--- a/Documentation/lguest/lguest.c
+++ b/Documentation/lguest/lguest.c
@@ -157,6 +157,9 @@
/* The routine to call when the Guest pings us. */
void (*handle_output)(int fd, struct virtqueue *me);
+
+ /* Outstanding buffers */
+ unsigned int inflight;
};
/* Remember the arguments to the program so we can "reboot" */
@@ -702,6 +705,7 @@
errx(1, "Looped descriptor");
} while ((i = next_desc(vq, i)) != vq->vring.num);
+ vq->inflight++;
return head;
}
@@ -719,6 +723,7 @@
/* Make sure buffer is written before we update index. */
wmb();
vq->vring.used->idx++;
+ vq->inflight--;
}
/* This actually sends the interrupt for this virtqueue */
@@ -726,8 +731,9 @@
{
unsigned long buf[] = { LHREQ_IRQ, vq->config.irq };
- /* If they don't want an interrupt, don't send one. */
- if (vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
+ /* If they don't want an interrupt, don't send one, unless empty. */
+ if ((vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
+ && vq->inflight)
return;
/* Send the Guest an interrupt tell them we used something up. */
@@ -1107,6 +1113,7 @@
vq->next = NULL;
vq->last_avail_idx = 0;
vq->dev = dev;
+ vq->inflight = 0;
/* Initialize the configuration. */
vq->config.num = num_descs;
@@ -1368,6 +1375,7 @@
/* Tell Guest what MAC address to use. */
add_feature(dev, VIRTIO_NET_F_MAC);
+ add_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY);
set_config(dev, sizeof(conf), &conf);
/* We don't need the socket any more; setup is done. */