From mboxrd@z Thu Jan 1 00:00:00 1970 From: Seth Forshee Subject: Re: [PATCH] xen-netfront: Remove BUGs on paged skb data which crosses a page boundary Date: Wed, 26 Nov 2014 21:53:50 -0600 Message-ID: <20141127035350.GA10833@ubuntu-mba51> References: <1416968904-70874-1-git-send-email-seth.forshee@canonical.com> <20141126.122812.223757363894961994.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: konrad.wilk@oracle.com, boris.ostrovsky@oracle.com, david.vrabel@citrix.com, zoltan.kiss@linaro.org, eric.dumazet@gmail.com, stefan.bader@canonical.com, xen-devel@lists.xenproject.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: David Miller Return-path: Content-Disposition: inline In-Reply-To: <20141126.122812.223757363894961994.davem@davemloft.net> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Wed, Nov 26, 2014 at 12:28:12PM -0500, David Miller wrote: > From: Seth Forshee > Date: Tue, 25 Nov 2014 20:28:24 -0600 > > > These BUGs can be erroneously triggered by frags which refer to > > tail pages within a compound page. The data in these pages may > > overrun the hardware page while still being contained within the > > compound page, but since compound_order() evaluates to 0 for tail > > pages the assertion fails. The code already iterates through > > subsequent pages correctly in this scenario, so the BUGs are > > unnecessary and can be removed. > > > > Fixes: f36c374782e4 ("xen/netfront: handle compound page fragments on transmit") > > Cc: # 3.7+ > > Signed-off-by: Seth Forshee > > Can I get some Xen developer reviews? Fwiw this issue was discussed previously and this was the recommended fix. http://article.gmane.org/gmane.linux.kernel/1825381 Since then I got some feedback from a tester that he didn't see any problems with the BUGs removed (actually replaced with a WARN so I know that he actually saw the condition which triggered the BUG). Thanks, Seth