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

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Date:	Wed, 20 Mar 2013 11:28:49 -0700
From:	Dirk Brandewie <dirk.brandewie@...il.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	dirk.brandewie@...il.com, 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 03/20/2013 11:28 AM, Rafael J. Wysocki wrote:
> 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.?
>

Sorry I saw right after I sent the mail that the bug report was missing

     https://bugzilla.redhat.com/show_bug.cgi?id=922923
     Reported-by: Josh Stone <jistone@...hat.com>

Would you like me to spin the patch?

> 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());
>>

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