From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: [PATCH] ACPI: Add fixups for AMD P-state figures. Date: Wed, 6 Mar 2013 10:51:12 -0500 Message-ID: <20130306155112.GA13118@phenom.dumpdata.com> References: <1362512728-28770-1-git-send-email-konrad.wilk@oracle.com> <51365401.4050205@oracle.com> <20130305213319.GA8235@phenom.dumpdata.com> <513710D1.2010803@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <513710D1.2010803@canonical.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Stefan Bader Cc: Boris Ostrovsky , xen-devel@lists.xensource.com, bp@suse.de List-Id: xen-devel@lists.xenproject.org On Wed, Mar 06, 2013 at 10:48:01AM +0100, Stefan Bader wrote: > On 05.03.2013 22:33, Konrad Rzeszutek Wilk wrote: > > On Tue, Mar 05, 2013 at 03:22:25PM -0500, Boris Ostrovsky wrote: > >> On 03/05/2013 02:45 PM, Konrad Rzeszutek Wilk wrote: > >>> This a copy-n-paste from two Linux git commits: > >>> > >>> - f594065faf4f9067c2283a34619fc0714e79a98d > >>> ACPI: Add fixups for AMD P-state figures > >>> - 9855d8ce41a7801548a05d844db2f46c3e810166 > >>> ACPI: Check MSR valid bit before using P-state frequencies > >>> > >>> The issue is that "some AMD systems may round the frequencies in > >>> ACPI tables to 100MHz boundaries. We canobtain the real > >>> frequencies from MSRs, so add a quirk to fix these frequencies up > >>> on AMD systems." (from f594065..) > >>> > >>> In discussion (around 9855d8..) "it turned out that indeed real > >>> HW/BIOSes may choose to not set the valid bit and thus mark the > >>> P-state as invalid. So this could be considered a fix for broken > >>> BIOSes that also works around the issue on Xen." (from 9855d8..) > >>> > >>> I've tested it under Dell Inc. PowerEdge T105 /0RR825, BIOS 1.3.2 > >>> 08/20/2008 where this quirk can indeed be observed. > >>> > >>> CC: stefan.bader@canonical.com > >>> CC: bp@suse.de > >>> CC: borislav.ostrovsky@oracle.com > >> > >> boris.ostrovsky@oracle.com > > > > Whoops! > > > > Here is an updated version: > > > > From 3b7584f0c3c91d073bd760a038d0091b3bf5a19b Mon Sep 17 00:00:00 2001 > > From: Konrad Rzeszutek Wilk > > Date: Tue, 5 Mar 2013 14:40:52 -0500 > > Subject: [PATCH] ACPI: Add fixups for AMD P-state figures. > > > > This a copy-n-paste from two Linux git commits: > > > > - f594065faf4f9067c2283a34619fc0714e79a98d > > ACPI: Add fixups for AMD P-state figures > > - 9855d8ce41a7801548a05d844db2f46c3e810166 > > ACPI: Check MSR valid bit before using P-state frequencies > > > > The issue is that "some AMD systems may round the frequencies in > > ACPI tables to 100MHz boundaries. We canobtain the real > > frequencies from MSRs, so add a quirk to fix these frequencies up > > on AMD systems." (from f594065..) > > > > In discussion (around 9855d8..) "it turned out that indeed real > > HW/BIOSes may choose to not set the valid bit and thus mark the > > P-state as invalid. So this could be considered a fix for broken > > BIOSes that also works around the issue on Xen." (from 9855d8..) > > Boris and Jan already pointed out more than I would have spotted. So it seems > the only thing left is the commit description. Well maybe it is just my way of > reading it but it feels like here the actual description/argument is missing. > > I think it might be that Xen gets the unmodified values from the ACPI parsing in > dom0 because it cannot/does not want to allow dom0 to read the MSR. Right. > Instead this patch will cause the frequencies to be adapted in the hypervisor. Correct. I will update the git commit with such wording and send out an updated patch shortly.