From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dan.rpsys.net (5751f4a1.skybroadband.com [87.81.244.161]) by mail.openembedded.org (Postfix) with ESMTP id 64DDC606BF for ; Thu, 10 Mar 2016 20:59:46 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by dan.rpsys.net (8.14.4/8.14.4/Debian-4.1ubuntu1) with ESMTP id u2AKxhut030271; Thu, 10 Mar 2016 20:59:43 GMT Received: from dan.rpsys.net ([127.0.0.1]) by localhost (dan.rpsys.net [127.0.0.1]) (amavisd-new, port 10024) with LMTP id e527zoQ2nLv7; Thu, 10 Mar 2016 20:59:43 +0000 (GMT) Received: from hex ([192.168.3.34]) (authenticated bits=0) by dan.rpsys.net (8.14.4/8.14.4/Debian-4.1ubuntu1) with ESMTP id u2AKxawR030266 (version=TLSv1/SSLv3 cipher=AES128-GCM-SHA256 bits=128 verify=NOT); Thu, 10 Mar 2016 20:59:38 GMT Message-ID: <1457643576.2804.228.camel@linuxfoundation.org> From: Richard Purdie To: Bruce Ashfield , Paul Gortmaker Date: Thu, 10 Mar 2016 20:59:36 +0000 In-Reply-To: <56E0F427.7030708@windriver.com> References: <2e6d2b75837731be983d888eaa82a9cfcf660e85.1455203562.git.bruce.ashfield@windriver.com> <1455287765.16142.321.camel@linuxfoundation.org> <1455291157.16142.323.camel@linuxfoundation.org> <1455352317.16142.344.camel@linuxfoundation.org> <1455383832.16142.365.camel@linuxfoundation.org> <20160302014146.GE20979@windriver.com> <56E07128.2060401@windriver.com> <1457558624.2804.181.camel@linuxfoundation.org> <56E0F427.7030708@windriver.com> X-Mailer: Evolution 3.16.5-1ubuntu3.1 Mime-Version: 1.0 Cc: "Hart, Darren" , "saul.wold" , poky@yoctoproject.org, openembedded-core Subject: Re: [poky] [PATCH 1/1] poky: update qemu* to prefer 4.4 kernel X-BeenThere: openembedded-core@lists.openembedded.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Patches and discussions about the oe-core layer List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 10 Mar 2016 20:59:48 -0000 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit On Wed, 2016-03-09 at 23:12 -0500, Bruce Ashfield wrote: > On 2016-03-09 4:23 PM, Richard Purdie wrote: > > On Wed, 2016-03-09 at 13:53 -0500, Bruce Ashfield wrote: > > > As another follow up. The thread can be summarized as "It doesn't > > > look like it should have worked before, and qemu's pat emulation > > > may be the issue'. > > > > > > The suggestion is to run with 'nopat', which is what Richard > > > originally > > > did. > > > > > > So I'm going to prep a patch that drops the kernel patch, and > > > leaves > > > nopat enabled on the qemu command line. That should get us put > > > back > > > together in a semi-permanent way. > > > > How sure are we this is a bug in QEMU's pat emulation? If that is > > the > > case we should file a bug against qemu and try and fix it rather > > than > > work around it... > > It could still be something that the kernel can work around, Toshi > did say: > > There is a matter of how qemu emulates CPU features. There is no > such > Intel CPU that supports PAT w/o MTRR. This is why the current code > assumes this dependency. > > Which is likely the trigger, we've send information about the cpu to > him, and with that there's a chance for a pat fix. > > He repeated our thought of running with 'nopat' while a fix is > considered. > > It may be some time before that happens, and I was going to test > with the kernel patch dropped, and nopat in the qemu boot args. If > that works, I'd rather run with that, and then revisit when (if) > there's more changes upstream. Reading the other thread, it looks like if MTRR is disabled, PAT needs to be disabled too. That sounds like a simple enough patch which is going upstream imminently so I think the preferred solution is to get that into our kernels and then drop my patch? Cheers, Richard