From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760036Ab3GaNcT (ORCPT ); Wed, 31 Jul 2013 09:32:19 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:47118 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759864Ab3GaN0E (ORCPT ); Wed, 31 Jul 2013 09:26:04 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Konrad Rzeszutek Wilk" , "Jan Beulich" Date: Wed, 31 Jul 2013 15:23:09 +0200 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [32/84] xen/io/ring.h: new macro to detect whether there are too many requests on the ring In-Reply-To: X-SA-Exim-Connect-IP: 151.216.67.181 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.50-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Jan Beulich commit 8d9256906a97c24e97e016482b9be06ea2532b05 upstream. 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 . Signed-off-by: Jan Beulich Signed-off-by: Konrad Rzeszutek Wilk Signed-off-by: Ben Hutchings --- include/xen/interface/io/ring.h | 5 +++++ 1 file changed, 5 insertions(+) --- 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; \