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| author | Jan Beulich <jbeulich@suse.com> | 2013-06-12 10:07:20 +0200 |
|---|---|---|
| committer | Jan Beulich <jbeulich@suse.com> | 2013-06-12 10:07:20 +0200 |
| commit | a63c57093b610e8707653fb2320f48e2ad5acbc2 (patch) | |
| tree | 85320636940b2f9a98a90af08ccc3ab2f1c13913 | |
| parent | f8e8fd56bd7d5675e8331b4ec74bae76c9dbf24e (diff) | |
| download | xen-a63c57093b610e8707653fb2320f48e2ad5acbc2.tar.gz xen-a63c57093b610e8707653fb2320f48e2ad5acbc2.tar.bz2 xen-a63c57093b610e8707653fb2320f48e2ad5acbc2.zip | |
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>
Acked-by: Keir Fraser <keir@xen.org>
| -rw-r--r-- | xen/include/public/io/ring.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/xen/include/public/io/ring.h b/xen/include/public/io/ring.h index d9884f5a0f..bdfb998cec 100644 --- a/xen/include/public/io/ring.h +++ b/xen/include/public/io/ring.h @@ -234,6 +234,10 @@ typedef struct __name##_back_ring __name##_back_ring_t #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 { \ xen_wmb(); /* back sees requests /before/ updated producer index */ \ (_r)->sring->req_prod = (_r)->req_prod_pvt; \ |