From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Egger Subject: Re: [PATCH] xen: provide pse36 cpuid bit Date: Fri, 28 Oct 2011 16:20:19 +0200 Message-ID: <4EAABA23.1000500@amd.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Keir Fraser Cc: "xen-devel@lists.xensource.com" , Tim Deegan List-Id: xen-devel@lists.xenproject.org On 10/27/11 17:30, Keir Fraser wrote: > On 27/10/2011 16:15, "Tim Deegan" wrote: > >> If you mean this: >> >> * PSE disabled / PSE36 >> * We don't support any modes other than PSE enabled, PSE36 disabled. >> * Neither of those would be hard to change, but we'd need to be able to >> * deal with shadows made in one mode and used in another. >> >> the worry was that we'd need a whole nother shadow mode to handle the >> case where one VCPU was in normal 32-bit and another was in PSE36 (since >> they can't share shadows). >> >> As it happens the current code does detect PSE-disabled in shadow mode >> but just DTRT for the current VCPU, so a mix of PSE-enabled and >> PSE-disabled VCPUs will get unpredicatble results from shadow >> pagetables. :( >> >> Which means that supporting PSE36 to the same degree (i.e. assuming all >> VCPUs behave the same, or if they don't they don't share pagetables) >> would be OK too. :) > > Ah, I see. Yes, I guessed it would be supported to just the same degree as > 'basic' PSE. The likelihood of pagetables being shared across different > pagetable-related CR4 settings? Not great, we hope. :-) Is the patch acceptable as it is ? PSE36 support for 32bit legacy mode can be done in a seperate patch. Christoph -- ---to satisfy European Law for business letters: Advanced Micro Devices GmbH Einsteinring 24, 85689 Dornach b. Muenchen Geschaeftsfuehrer: Alberto Bozzo, Andrew Bowd Sitz: Dornach, Gemeinde Aschheim, Landkreis Muenchen Registergericht Muenchen, HRB Nr. 43632