From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: [PATCH v2 10/12] xen/iommu: smmu: Check for duplicate stream IDs when registering master devices Date: Tue, 27 Jan 2015 17:44:35 +0000 Message-ID: <1422380675.16180.38.camel@citrix.com> References: <1421418247-30068-1-git-send-email-julien.grall@linaro.org> <1421418247-30068-11-git-send-email-julien.grall@linaro.org> <54C7C263.7090806@linaro.org> <54C7CC04.9000509@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta14.messagelabs.com ([193.109.254.103]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1YGABu-0003Xh-Ad for xen-devel@lists.xenproject.org; Tue, 27 Jan 2015 17:44:42 +0000 In-Reply-To: <54C7CC04.9000509@linaro.org> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Julien Grall Cc: Stefano Stabellini , tim@xen.org, Andreas Herrmann , stefano.stabellini@citrix.com, Andreas Herrmann , xen-devel@lists.xenproject.org List-Id: xen-devel@lists.xenproject.org On Tue, 2015-01-27 at 17:33 +0000, Julien Grall wrote: > On 27/01/15 17:02, Stefano Stabellini wrote: > > On Tue, 27 Jan 2015, Julien Grall wrote: > >> On 27/01/15 16:30, Stefano Stabellini wrote: > >>> On Fri, 16 Jan 2015, Julien Grall wrote: > >>>> From: Andreas Herrmann > >>>> > >>>> If DT information lists one stream ID twice for the master devices of > >>>> an SMMU this can cause a multi match when stream ID matching is used. > >>>> For stream ID indexing this might trigger an overwrite of an S2CR that > >>>> is already in use. > >>>> > >>>> So better check for duplicates when DT information is parsed. > >>>> > >>>> Taken from the linux ML: > >>>> http://lists.infradead.org/pipermail/linux-arm-kernel/2014-January/226099.html > >>>> > >>>> Cc: Andreas Herrmann > >>>> Signed-off-by: Andreas Herrmann > >>>> Signed-off-by: Julien Grall > >>> > >>> Why didn't you just take a more recent version of the Linux smmu driver? > >> > >> The SMMU driver very is recent (see commit in the previous patch)... > >> Just this patch has never reached upstream. > > > > That is not good. It might be worth to wait for it to go upstream. > > The patch was sent one year ago. Just before Calxeda was shutdown. > > This is a requirement for the following patch. Do you think the other > patch should be upstream to Linux before? In general we should be reluctant to diverge over these things, since it just ends up making things harder for us in the future (e.g. the next resync or the one after). Is the issue being fixed here specific to Calxeda? e.g. is duplicate stream ids a h/w bug which has yet to be observed elsewhere or is it a valid configuration per the h/w specs which it just happens only Calxeda implemented? Unless it's a h/w bug I don't see why it couldn't go upstream first. Even if it is it might still stand a chance. > If so, Calxeda server won't be able to use properly SMMU. > > Even though the server will never be used, I do all my SMMU development > on it. The fact that Calxeda are no longer around doesn't in itself preclude getting these patches upstreamed. After all, no one is deleting CX support and some people do have them (not just us). It's hardly the most obscure platform supported by Linux... Ian.