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

From: Boris Ostrovsky
Date: Mon Jan 21 2013 - 19:01:48 EST




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);


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