Re: [TEST PATCH] cpufreq: intel_pstate: Workaround to for wrong ACPI perf table entry

[Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>]

Hi Borislav,

Sorry for the trouble. Please test the patch and let me know if it
fixes your issue.
In my description the value 0x1d00 should be 0x2400, I was simulating
on another system with max as 0x1d00.

Thanks,
Srinivas

On Tue, 2015-11-17 at 15:00 -0800, Srinivas Pandruvada wrote:
> With the implementation of ACPI _PSS and _PPC processing in the Intel
> P
> state driver, a bad ACPI configuration can impact max/min states. For
> example as reported by Borislav Petkov <bp@alien8.de>, the log shows:
> 
> [    0.826119] intel_pstate: default limits 0xc 0x1d 0x24
> [    0.827000] intel_pstate: CPU0 - ACPI _PSS perf data
> [    0.827020]      *P0: 2901 MHz, 35000 mW, 0xff00
> The above control value of 0xff00, is invalid. The first entry sets
> the
> max control value for turbo with a max non turbo frequency + 1 MHz.
> Here
> the control values should be 0x1d00. intel_pstate_set_policy()
> depends on
> this control value in setting correct max pstate.
> Two fixes have been done here:
> - If the control value is invalid then use the physical max turbo as
> the
> max. Here 0xff00 will be changed to 0x1d00
> - Always reset the limits->min_perf_ctl and limits->max_perf_ctl, so
> that
> we will not use last value. In this case even if entry is not found
> the
> _PSS it will fallback to limits->max_perf and limits-> limits
> ->max_perf.
> 
> Reported-by: Borislav Petkov <bp@alien8.de>
> Signed-off-by: Srinivas Pandruvada <
> srinivas.pandruvada@linux.intel.com>
> ---
>  drivers/cpufreq/intel_pstate.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/cpufreq/intel_pstate.c
> b/drivers/cpufreq/intel_pstate.c
> index d3159f0..fc99e97 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -311,6 +311,13 @@ static int intel_pstate_init_perf_limits(struct
> cpufreq_policy *policy)
>  		 * correct max turbo frequency based on the turbo
> ratio.
>  		 * Also need to convert to MHz as _PSS freq is in
> MHz.
>  		 */
> +		if (turbo_pss_ctl > cpu->pstate.turbo_pstate) {
> +			/* We hava an invalid control value here */
> +			turbo_pss_ctl = cpu->pstate.turbo_pstate;
> +			cpu->acpi_perf_data.states[0].control =
> +							turbo_pss_ct
> l << 8;
> +		}
> +
>  		cpu->acpi_perf_data.states[0].core_frequency =
>  				turbo_pss_ctl * cpu->pstate.scaling
> / 1000;
>  	}
> @@ -1272,6 +1279,8 @@ static int intel_pstate_set_policy(struct
> cpufreq_policy *policy)
>  
>  #if IS_ENABLED(CONFIG_ACPI)
>  	cpu = all_cpu_data[policy->cpu];
> +	limits->min_perf_ctl = 0;
> +	limits->max_perf_ctl = 0;
>  	for (i = 0; i < cpu->acpi_perf_data.state_count; i++) {
>  		int control;
>