Messages in this thread | | | Date | Wed, 16 Jan 2013 15:34:52 +0100 | From | Stefan Bader <> | Subject | Re: [Xen-devel] kernel 3.7+ cpufreq regression on AMD system running as dom0 |
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On 01/16/2013 11:26 AM, Jan Beulich wrote: >>>> On 15.01.13 at 18:53, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote: >> On Mon, Jan 14, 2013 at 05:34:45PM +0100, Borislav Petkov wrote: >>> On Mon, Jan 14, 2013 at 04:58:54PM +0100, Stefan Bader wrote: >>>> --- 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 >>>> 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 & 0x8000000)) >>>> + return; >>> >>> I don't think that's the right change - this is fixing baremetal so that >>> it works on xen. And besides, this code was in powernow-k8 before so I'm >>> wondering why did it work then. >> >> Powernow-k8 only populated the cpufreq policy information. This library >> (processor_perflib) is the generic library used for ACPI P-states parsing. >> This specific function (acpi_processor_get_performance_states) is just >> used to fetch and parse the P-states. >> >> Xen-acpi-processor (which we use to upload the P and C-states to the >> hypervisor) ends up calling this library to parse the P-states >> and this unfortunate quirk clamps the P-states based on the MSRS. >> >> It is odd that this CPU specific quirk got added in this generic >> library. Is there no ACPI quirk system similar to how DMI quirks >> are handled? >> >> Anyhow, I think this patch makes sense - it makes sure that the >> MSR value is sane. >> >> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> > > Did someone actually _test_ that patch? I ask because the mask > used (0x8000000) doesn't check bit 63 as the comment says, but > bit 59 instead... > > Jan > Not this version which I did at the end of a day to have a cleaned up version to discuss. And obviously I managed to get the number of zeros wrong. :(
The comment is right and it should be 0x80000000
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