From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753392Ab3AUMWa (ORCPT ); Mon, 21 Jan 2013 07:22:30 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:57018 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752573Ab3AUMW2 (ORCPT ); Mon, 21 Jan 2013 07:22:28 -0500 Message-ID: <50FD32FA.7010306@canonical.com> Date: Mon, 21 Jan 2013 12:22:18 +0000 From: Stefan Bader User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130105 Thunderbird/17.0.2 MIME-Version: 1.0 To: Borislav Petkov , Konrad Rzeszutek Wilk , Andre Przywara , "xen-devel@lists.xensource.com" , Linux Kernel Mailing List , "Rafael J. Wysocki" , Matthew Garrett Subject: Re: kernel 3.7+ cpufreq regression on AMD system running as dom0 References: <50F42B3E.7090602@canonical.com> <20130114163445.GA4867@liondog.tnic> <20130115175305.GA12449@phenom.dumpdata.com> <20130115181839.GC8101@liondog.tnic> <20130118190015.GC11351@phenom.dumpdata.com> <20130118200331.GF4062@pd.tnic> In-Reply-To: <20130118200331.GF4062@pd.tnic> Content-Type: multipart/mixed; boundary="------------010500090408050606080507" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is a multi-part message in MIME format. --------------010500090408050606080507 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 01/18/2013 08:03 PM, Borislav Petkov wrote: > On Fri, Jan 18, 2013 at 02:00:15PM -0500, Konrad Rzeszutek Wilk wrote: >> I did not explain myself well. The fix is OK - it just that the >> hypervisor causes the quirk to not work correctly. Hmm, I wonder if >> there BIOSes that do the same thing (cause the MSR to return 0). Per >> you estimation of BIOS quality, it seems that this could happen. > > Yeah, I don't think there's a limit to the amount of SNAFU a BIOS can > cause :-). > So for having the "check for sensible BIOS" in mainline I refreshed the patch (fixed the bit test, and actually tested it this time) and also added some hopefully sensible explanation to it (attached below). Should I send it to acpi lists or would that have to go via an Andre? -Stefan From 6e2fc8291c91339123a37162382d8b08b50867ba Mon Sep 17 00:00:00 2001 From: Stefan Bader Date: Mon, 14 Jan 2013 16:17:00 +0100 Subject: [PATCH] ACPI: Check MSR valid bit before using P-state frequencies To fix incorrect P-state frequencies which can happen on some AMD systems f594065faf4f9067c2283a34619fc0714e79a98d "ACPI: Add fixups for AMD P-state figures" introduced a quirk to obtain the correct values by reading from AMD specific MSRs. This did cause a regression when running a kernel using that quirk under Xen which does (currently) not pass on the contents of the HW but 0. And this seems to cause a failure to initialize the ondemand governour (hard to say for sure as all P-states appear to run at the same frequency). While this should also be fixed in the hypervisor (to allow a guest to read that MSR), this patch is intended to work around the issue in the meantime. In discussion 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. Signed-off-by: Stefan Bader Cc: stable@vger.kernel.org # v3.7.. --- drivers/acpi/processor_perflib.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c index 836bfe0..41f4bdac 100644 --- a/drivers/acpi/processor_perflib.c +++ b/drivers/acpi/processor_perflib.c @@ -340,6 +340,9 @@ static void amd_fixup_frequency(struct acpi_processor_px *px, int i) if ((boot_cpu_data.x86 == 0x10 && boot_cpu_data.x86_model < 10) || boot_cpu_data.x86 == 0x11) { rdmsr(MSR_AMD_PSTATE_DEF_BASE + index, lo, hi); + /* Bit 63 indicates whether contents are valid */ + if (!(hi & 0x80000000)) + return; fid = lo & 0x3f; did = (lo >> 6) & 7; if (boot_cpu_data.x86 == 0x10) -- 1.8.0 --------------010500090408050606080507 Content-Type: text/x-diff; name="0001-ACPI-Check-MSR-valid-bit-before-using-P-state-freque.patch" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename*0="0001-ACPI-Check-MSR-valid-bit-before-using-P-state-freque.pa"; filename*1="tch" >>From 6e2fc8291c91339123a37162382d8b08b50867ba Mon Sep 17 00:00:00 2001 From: Stefan Bader Date: Mon, 14 Jan 2013 16:17:00 +0100 Subject: [PATCH] ACPI: Check MSR valid bit before using P-state frequencies To fix incorrect P-state frequencies which can happen on some AMD systems f594065faf4f9067c2283a34619fc0714e79a98d "ACPI: Add fixups for AMD P-state figures" introduced a quirk to obtain the correct values by reading from AMD specific MSRs. This did cause a regression when running a kernel using that quirk under Xen which does (currently) not pass on the contents of the HW but 0. And this seems to cause a failure to initialize the ondemand governour (hard to say for sure as all P-states appear to run at the same frequency). While this should also be fixed in the hypervisor (to allow a guest to read that MSR), this patch is intended to work around the issue in the meantime. In discussion 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. Signed-off-by: Stefan Bader Cc: stable@vger.kernel.org # v3.7.. --- drivers/acpi/processor_perflib.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c index 836bfe0..41f4bdac 100644 --- a/drivers/acpi/processor_perflib.c +++ b/drivers/acpi/processor_perflib.c @@ -340,6 +340,9 @@ static void amd_fixup_frequency(struct acpi_processor_px *px, int i) if ((boot_cpu_data.x86 == 0x10 && boot_cpu_data.x86_model < 10) || boot_cpu_data.x86 == 0x11) { rdmsr(MSR_AMD_PSTATE_DEF_BASE + index, lo, hi); + /* Bit 63 indicates whether contents are valid */ + if (!(hi & 0x80000000)) + return; fid = lo & 0x3f; did = (lo >> 6) & 7; if (boot_cpu_data.x86 == 0x10) -- 1.8.0 --------------010500090408050606080507--