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authorRusty Russell <rusty@rustcorp.com.au>2008-02-04 23:49:59 -0500
committerRusty Russell <rusty@rustcorp.com.au>2008-02-04 23:50:00 +1100
commit426e3e0af5d2473e67d4256fc1340b7faebd1cc7 (patch)
tree29912e63889e45307f41ef08116ecd895b17e21c /Documentation/lguest
parent3309daaad724dd08eb598bf9c12b7bb9daddd706 (diff)
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virtio: clarify NO_NOTIFY flag usage
The other side (host) can set the NO_NOTIFY flag as an optimization, to say "no need to kick me when you add things". Make it clear that this is advisory only; especially that we should always notify when the ring is full. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Diffstat (limited to 'Documentation/lguest')
-rw-r--r--Documentation/lguest/lguest.c9
1 files changed, 5 insertions, 4 deletions
diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c
index 4df1804169dc..8ff2d8bc690a 100644
--- a/Documentation/lguest/lguest.c
+++ b/Documentation/lguest/lguest.c
@@ -923,10 +923,10 @@ static void handle_output(int fd, unsigned long addr)
/* Check each virtqueue. */
for (i = devices.dev; i; i = i->next) {
for (vq = i->vq; vq; vq = vq->next) {
- if (vq->config.pfn == addr/getpagesize()
- && vq->handle_output) {
+ if (vq->config.pfn == addr/getpagesize()) {
verbose("Output to %s\n", vq->dev->name);
- vq->handle_output(fd, vq);
+ if (vq->handle_output)
+ vq->handle_output(fd, vq);
return;
}
}
@@ -1068,7 +1068,8 @@ static void add_virtqueue(struct device *dev, unsigned int num_descs,
* virtqueue. */
vq->handle_output = handle_output;
- /* Set the "Don't Notify Me" flag if we don't have a handler */
+ /* As an optimization, set the advisory "Don't Notify Me" flag if we
+ * don't have a handler */
if (!handle_output)
vq->vring.used->flags = VRING_USED_F_NO_NOTIFY;
}