linux-kernel - Re: [PATCH] intel_pstate: Fix MSR_CONFIG_TDP_x addressing in core_get_max

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Date:	Fri, 08 Jul 2016 12:39:07 -0700
From:	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To:	Jan Kiszka <jan.kiszka@...mens.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Cc:	Kristen Carlson Accardi <kristen@...ux.intel.com>
Subject: Re: [PATCH] intel_pstate: Fix MSR_CONFIG_TDP_x addressing in
 core_get_max_pstate

On Fri, 2016-07-08 at 20:42 +0200, Jan Kiszka wrote:
> If MSR_CONFIG_TDP_CONTROL is locked, we currently try to address some
> MSR 0x80000648 or so. Mask out the relevant level bits 0 and 1.
> 
> Found while running over the Jailhouse hypervisor which became upset
> about this strange MSR index.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@...mens.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>

> ---
>  drivers/cpufreq/intel_pstate.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/cpufreq/intel_pstate.c
> b/drivers/cpufreq/intel_pstate.c
> index 1fa1a32..1b15917 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -944,7 +944,7 @@ static int core_get_max_pstate(void)
>  			if (err)
>  				goto skip_tar;
>  
> -			tdp_msr = MSR_CONFIG_TDP_NOMINAL + tdp_ctrl;
> +			tdp_msr = MSR_CONFIG_TDP_NOMINAL + (tdp_ctrl
> & 0x3);
>  			err = rdmsrl_safe(tdp_msr, &tdp_ratio);
>  			if (err)
>  				goto skip_tar;