Re: [Xen-devel] [PATCH] ACPI: Add fixups for AMD P-state figures.

[Stefan Bader <stefan.bader@xxxxxxxxxxxxx>]

On 06.03.2013 22:37, Konrad Rzeszutek Wilk wrote:
> On Wed, Mar 06, 2013 at 10:51:12AM -0500, Konrad Rzeszutek Wilk wrote:
>> On Wed, Mar 06, 2013 at 10:48:01AM +0100, Stefan Bader wrote:
>>> On 05.03.2013 22:33, Konrad Rzeszutek Wilk wrote:
>>>> On Tue, Mar 05, 2013 at 03:22:25PM -0500, Boris Ostrovsky wrote:
>>>>> On 03/05/2013 02:45 PM, Konrad Rzeszutek Wilk wrote:
>>>>>> This a copy-n-paste from two Linux git commits:
>>>>>>
>>>>>> - f594065faf4f9067c2283a34619fc0714e79a98d
>>>>>>   ACPI: Add fixups for AMD P-state figures
>>>>>> - 9855d8ce41a7801548a05d844db2f46c3e810166
>>>>>>   ACPI: Check MSR valid bit before using P-state frequencies
>>>>>>
>>>>>> The issue is that "some AMD systems may round the frequencies in
>>>>>> ACPI tables to 100MHz boundaries. We canobtain the real
>>>>>> frequencies from MSRs, so add a quirk to fix these frequencies up
>>>>>> on AMD systems." (from f594065..)
>>>>>>
>>>>>> In discussion (around 9855d8..) "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." (from 9855d8..)
>>>>>>
>>>>>> I've tested it under Dell Inc. PowerEdge T105 /0RR825, BIOS 1.3.2
>>>>>> 08/20/2008 where this quirk can indeed be observed.
>>>>>>
>>>>>> CC: stefan.bader@xxxxxxxxxxxxx
>>>>>> CC: bp@xxxxxxx
>>>>>> CC: borislav.ostrovsky@xxxxxxxxxx
>>>>>
>>>>> boris.ostrovsky@xxxxxxxxxx
>>>>
>>>> Whoops!
>>>>
>>>> Here is an updated version:
> 
> 
> From b704d4419e9e483922382d2339bd41c245f435e1 Mon Sep 17 00:00:00 2001
> From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Date: Tue, 5 Mar 2013 14:40:52 -0500
> Subject: [PATCH] ACPI: Add fixups for AMD P-state figures.
> 
> In the Linux kernel, these two git commits:
> 
> - f594065faf4f9067c2283a34619fc0714e79a98d
>   ACPI: Add fixups for AMD P-state figures
> - 9855d8ce41a7801548a05d844db2f46c3e810166
>   ACPI: Check MSR valid bit before using P-state frequencies
> 
> Try to fix the the issue that "some AMD systems may round the
> frequencies in ACPI tables to 100MHz boundaries. We can obtain the real
> frequencies from MSRs, so add a quirk to fix these frequencies up
> on AMD systems." (from f594065..)
> 
> In discussion (around 9855d8..) "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." (from 9855d8..)
> 
> which is great for Linux. Unfortunatly the Linux kernel, when
> it tries to do the RDMSR under Xen it fails to get the right
> value (it gets zero) as Xen traps it and returns zero. Hence
> when dom0 uploads the P-states they will be unmodified and
> we should take care of updating the frequencies with the right
> values.
> 
> I've tested it under Dell Inc. PowerEdge T105 /0RR825, BIOS 1.3.2
> 08/20/2008 where this quirk can be observed (x86 == 0x10, model == 2).
> Also on other AMD (x86 == 0x12, A8-3850; x86 = 0x14, AMD E-350) to
> make sure the quirk is not applied there.
> 
> CC: stefan.bader@xxxxxxxxxxxxx
> CC: bp@xxxxxxx
> CC: boris.ostrovsky@xxxxxxxxxx
> [v1: Indent, #define, and email changes per Boris's review]
> [v2: Redid the x86+model check, updated description]
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> ---
>  xen/arch/x86/acpi/cpufreq/powernow.c | 36 
> ++++++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
> 
> diff --git a/xen/arch/x86/acpi/cpufreq/powernow.c 
> b/xen/arch/x86/acpi/cpufreq/powernow.c
> index a9b7792..8c96fe0 100644
> --- a/xen/arch/x86/acpi/cpufreq/powernow.c
> +++ b/xen/arch/x86/acpi/cpufreq/powernow.c
> @@ -147,6 +147,40 @@ static int powernow_cpufreq_target(struct cpufreq_policy 
> *policy,
>      return 0;
>  }
>  
> +static void amd_fixup_frequency(struct xen_processor_px *px)
> +{
> +    u32 hi, lo, fid, did;
> +    int index = px->control & 0x00000007;
> +
> +    if (!(boot_cpu_data.x86 == 0x10 && boot_cpu_data.x86_model < 10) &&
> +        !(boot_cpu_data.x86 == 0x11))
> +        return;
> +
> +    rdmsr(MSR_PSTATE_DEF_BASE + index, lo, hi);
> +    /*
> +     * MSR C001_0064+:
> +     * Bit 63: PstateEn. Read-write. If set, the P-state is valid.
> +     */
> +    if (!(hi & (1UL << 31)))
> +        return;
> +
> +    fid = lo & 0x3f;
> +    did = (lo >> 6) & 7;
> +    if (boot_cpu_data.x86 == 0x10)
> +        px->core_frequency = (100 * (fid + 16)) >> did;
> +    else
> +        px->core_frequency = (100 * (fid + 8)) >> did;
> +}
> +
> +static void amd_fixup_freq(struct processor_performance *perf)
> +{
> +
> +    unsigned int i;
> +
> +    for (i = 0; i < perf->state_count; i++)
> +        amd_fixup_frequency(&perf->states[i]);
> +
> +}
>  static int powernow_cpufreq_verify(struct cpufreq_policy *policy)
>  {
>      struct acpi_cpufreq_data *data;
> @@ -253,6 +287,8 @@ static int powernow_cpufreq_cpu_init(struct 
> cpufreq_policy *policy)
>  
>      policy->governor = cpufreq_opt_governor ? : CPUFREQ_DEFAULT_GOVERNOR;
>  
> +    amd_fixup_freq(perf);
> +
>      /* table init */
>      for (i = 0; i < perf->state_count && i <= max_hw_pstate; i++) {
>          if (i > 0 && perf->states[i].core_frequency >=
> 

That would look good to me. Using Thunderbird I do not want to make any
statement about indentation.

-Stefan

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