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authorJan Beulich <jbeulich@suse.com>2013-06-17 15:16:33 -0400
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2013-06-17 15:17:15 -0400
commit8d9256906a97c24e97e016482b9be06ea2532b05 (patch)
treed6e1828f08344fa7f183ea9deddb8b898b26d5ab /include/xen/interface
parent604c499cbbcc3d5fe5fb8d53306aa0fae1990109 (diff)
xen/io/ring.h: new macro to detect whether there are too many requests on the ring
Backends may need to protect themselves against an insane number of produced requests stored by a frontend, in case they iterate over requests until reaching the req_prod value. There can't be more requests on the ring than the difference between produced requests and produced (but possibly not yet published) responses. This is a more strict alternative to a patch previously posted by Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>. Signed-off-by: Jan Beulich <jbeulich@suse.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'include/xen/interface')
-rw-r--r--include/xen/interface/io/ring.h5
1 files changed, 5 insertions, 0 deletions
diff --git a/include/xen/interface/io/ring.h b/include/xen/interface/io/ring.h
index 75271b9a8f61..7d28aff605c7 100644
--- a/include/xen/interface/io/ring.h
+++ b/include/xen/interface/io/ring.h
@@ -188,6 +188,11 @@ struct __name##_back_ring { \
#define RING_REQUEST_CONS_OVERFLOW(_r, _cons) \
(((_cons) - (_r)->rsp_prod_pvt) >= RING_SIZE(_r))
+/* Ill-behaved frontend determination: Can there be this many requests? */
+#define RING_REQUEST_PROD_OVERFLOW(_r, _prod) \
+ (((_prod) - (_r)->rsp_prod_pvt) > RING_SIZE(_r))
+
+
#define RING_PUSH_REQUESTS(_r) do { \
wmb(); /* back sees requests /before/ updated producer index */ \
(_r)->sring->req_prod = (_r)->req_prod_pvt; \