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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 /include/linux/virtio_ring.h
parent3309daaad724dd08eb598bf9c12b7bb9daddd706 (diff)
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 'include/linux/virtio_ring.h')
-rw-r--r--include/linux/virtio_ring.h8
1 files changed, 6 insertions, 2 deletions
diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h
index ea3be89a0e83..abe481ed990e 100644
--- a/include/linux/virtio_ring.h
+++ b/include/linux/virtio_ring.h
@@ -15,9 +15,13 @@
/* This marks a buffer as write-only (otherwise read-only). */
#define VRING_DESC_F_WRITE 2
-/* This means don't notify other side when buffer added. */
+/* The Host uses this in used->flags to advise the Guest: don't kick me when
+ * you add a buffer. It's unreliable, so it's simply an optimization. Guest
+ * will still kick if it's out of buffers. */
#define VRING_USED_F_NO_NOTIFY 1
-/* This means don't interrupt guest when buffer consumed. */
+/* The Guest uses this in avail->flags to advise the Host: don't interrupt me
+ * when you consume a buffer. It's unreliable, so it's simply an
+ * optimization. */
#define VRING_AVAIL_F_NO_INTERRUPT 1
/* Virtio ring descriptors: 16 bytes. These can chain together via "next". */