Patchwork [RFC,v9,13/27] virtio-blk: Increase max requests for indirect vring

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Submitter Stefan Hajnoczi
Date July 18, 2012, 3:07 p.m.
Message ID <1342624074-24650-14-git-send-email-stefanha@linux.vnet.ibm.com>
Download mbox | patch
Permalink /patch/171734/
State New
Headers show

Comments

Stefan Hajnoczi - July 18, 2012, 3:07 p.m.
With indirect vring descriptors, one can no longer assume that the
maximum number of requests is VRING_MAX / 2 (outhdr and inhdr).  Now a
single indirect descriptor can contain the outhdr and inhdr so max
requests becomes VRING_MAX.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 hw/virtio-blk.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Patch

diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
index 591eace..7ae3c56 100644
--- a/hw/virtio-blk.c
+++ b/hw/virtio-blk.c
@@ -26,7 +26,9 @@ 
 enum {
     SEG_MAX = 126,                  /* maximum number of I/O segments */
     VRING_MAX = SEG_MAX + 2,        /* maximum number of vring descriptors */
-    REQ_MAX = VRING_MAX / 2,        /* maximum number of requests in the vring */
+    REQ_MAX = VRING_MAX,            /* maximum number of requests in the vring,
+                                     * is VRING_MAX / 2 with traditional and
+                                     * VRING_MAX with indirect descriptors */
 };
 
 typedef struct {