Messages in this thread | | | Date | Fri, 25 Jan 2013 18:45:29 +0100 | From | Roger Pau Monné <> | Subject | Re: [Xen-devel] [PATCH 2/3] xen/ring: Add a new macro to detect whether there is an overflow in requests and response. |
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On 25/01/13 18:32, Konrad Rzeszutek Wilk wrote: > We want to be able to exit if the difference between the request > produced (what the frontend tells us) and the requests consumed > (what we have so far processed) is greater than the ring size. > > If so, we should terminate the loop as the request produced > is not trusted and it means it is bogus. > > Cc: stable@vger.kernel.org > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> > --- > include/xen/interface/io/ring.h | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/include/xen/interface/io/ring.h b/include/xen/interface/io/ring.h > index 75271b9..1114dde 100644 > --- a/include/xen/interface/io/ring.h > +++ b/include/xen/interface/io/ring.h > @@ -188,6 +188,12 @@ struct __name##_back_ring { \ > #define RING_REQUEST_CONS_OVERFLOW(_r, _cons) \ > (((_cons) - (_r)->rsp_prod_pvt) >= RING_SIZE(_r)) > > +/* Loop termination condition: Is the difference between request produced > + * and request consumed greater than the ring size. If so, terminate the > + * loop. */ > +#define RING_REQUEST_PROD_OVERFLOW(_r, _cons, _prod) \ > + (((_prod) - (_prod)) > RING_SIZE(_r))
Shouldn't the second _prod be _cons?
> + > #define RING_PUSH_REQUESTS(_r) do { \ > wmb(); /* back sees requests /before/ updated producer index */ \ > (_r)->sring->req_prod = (_r)->req_prod_pvt; \ >
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