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

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Message-ID: <50FDD6F1.5030208@amd.com>
Date:	Mon, 21 Jan 2013 19:01:53 -0500
From:	Boris Ostrovsky <boris.ostrovsky@....com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Borislav Petkov <bp@...en8.de>,
	Stefan Bader <stefan.bader@...onical.com>,
	Andre Przywara <andre@...rep.de>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Matthew Garrett <mjg@...hat.com>
Subject: Re: [Xen-devel] kernel 3.7+ cpufreq regression on AMD system running
 as dom0



On 01/18/2013 02:00 PM, Konrad Rzeszutek Wilk wrote:
>
> So something like this in the hypervisor maybe (not even tested):
>
> diff --git a/xen/arch/x86/acpi/cpufreq/powernow.c b/xen/arch/x86/acpi/cpufreq/powernow.c
> index a9b7792..54e7808 100644
> --- a/xen/arch/x86/acpi/cpufreq/powernow.c
> +++ b/xen/arch/x86/acpi/cpufreq/powernow.c
> @@ -146,7 +146,40 @@ static int powernow_cpufreq_target(struct cpufreq_policy *policy,
>
>       return 0;
>   }
> +#define MSR_AMD_PSTATE_DEF_BASE     0xc0010064
> +static void amd_fixup_frequency(struct xen_processor_px *px, int i)
> +{
> +	u32 hi, lo, fid, did;
> +	int index = px->control & 0x00000007;
> +
> +	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
> +		return;
> +
> +	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)
> +			px->core_frequency = (100 * (fid + 0x10)) >> did;
> +		else
> +			px->core_frequency = (100 * (fid + 8)) >> did;
> +	}
> +}
> +
> +static void amd_fixup_freq(struct processor_performance *perf)
> +{
>
> +    int i;
> +
> +    for (i = 0; i < perf->state_count; i++)
> +        amd_fixup_frequency(perf->states, i);

amd_fixup_frequency(&perf->states[i]) will walk P-states.

> +
> +}
>   static int powernow_cpufreq_verify(struct cpufreq_policy *policy)
>   {
>       struct acpi_cpufreq_data *data;
> @@ -158,6 +191,8 @@ static int powernow_cpufreq_verify(struct cpufreq_policy *policy)
>
>       perf = &processor_pminfo[policy->cpu]->perf;
>
> +    amd_fixup_freq(perf);

Maybe move to powernow_cpufreq_cpu_init(), although this works too.


-boris


> +
>       cpufreq_verify_within_limits(policy, 0,
>           perf->states[perf->platform_limit].core_frequency * 1000);
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@...ts.xen.org
> http://lists.xen.org/xen-devel
>

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