linux-kernel - Re: [PATCH] cpufreq/intel_pstate: Add function to check that all MSR's are valid

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Message-ID: <5818534.Fj7AtdhPq1@vostro.rjw.lan>
Date:	Wed, 20 Mar 2013 19:28:43 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	dirk.brandewie@...il.com
Cc:	linux-kernel@...r.kernel.org, cpufreq@...r.kernel.org,
	Dirk Brandewie <dirk.j.brandewie@...el.com>
Subject: Re: [PATCH] cpufreq/intel_pstate: Add function to check that all MSR's are valid

On Wednesday, March 20, 2013 09:17:24 AM dirk.brandewie@...il.com wrote:
> From: Dirk Brandewie <dirk.brandewie@...il.com>
> 
> Some VMs seem to try to implement some MSRs but not all the registers
> the driver needs.  Check to make sure all the MSR that we need are
> available. If any of the required MSRs are not available refuse to
> load.
> 
> Signed-off-by: Dirk Brandewie <dirk.j.brandewie@...el.com>

Is this needed for v3.9?  Any pointers to bug reports etc.?

Rafael


> ---
>  drivers/cpufreq/intel_pstate.c |   26 ++++++++++++++++++++++++++
>  1 files changed, 26 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index f6dd1e7..cd9c5f4 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -752,6 +752,29 @@ static struct cpufreq_driver intel_pstate_driver = {
>  
>  static int __initdata no_load;
>  
> +static int intel_pstate_msrs_not_valid(void)
> +{
> +	/* Check that all the msr's we are using are valid. */
> +	u64 aperf, mperf, tmp;
> +
> +	rdmsrl(MSR_IA32_APERF, aperf);
> +	rdmsrl(MSR_IA32_MPERF, mperf);
> +
> +	if (!intel_pstate_min_pstate() ||
> +		!intel_pstate_max_pstate() ||
> +		!intel_pstate_turbo_pstate())
> +		return -ENODEV;
> +
> +	rdmsrl(MSR_IA32_APERF, tmp);
> +	if (!(tmp - aperf))
> +		return -ENODEV;
> +
> +	rdmsrl(MSR_IA32_MPERF, tmp);
> +	if (!(tmp - mperf))
> +		return -ENODEV;
> +
> +	return 0;
> +}
>  static int __init intel_pstate_init(void)
>  {
>  	int cpu, rc = 0;
> @@ -764,6 +787,9 @@ static int __init intel_pstate_init(void)
>  	if (!id)
>  		return -ENODEV;
>  
> +	if (intel_pstate_msrs_not_valid())
> +		return -ENODEV;
> +
>  	pr_info("Intel P-state driver initializing.\n");
>  
>  	all_cpu_data = vmalloc(sizeof(void *) * num_possible_cpus());
> 
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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