linux-kernel - Re: [Xen-devel] kernel 3.7+ cpufreq regression on AMD system running as dom0

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Date:	Mon, 14 Jan 2013 16:55:36 +0000
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Borislav Petkov" <bp@...en8.de>,
	"Andre Przywara" <andre@...rep.de>,
	"Stefan Bader" <stefan.bader@...onical.com>
Cc:	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"Konrad Rzeszutek Wilk" <konrad.wilk@...cle.com>,
	"Matthew Garrett" <mjg@...hat.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] kernel 3.7+ cpufreq regression on AMD system
 running as dom0

>>> On 14.01.13 at 17:34, Borislav Petkov <bp@...en8.de> 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.

Because the driver doesn't get loaded in that case?

Jan

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