Re: [Xen-devel] [PATCH 1 of 2] traps: AMD PM RDMSRs (MSR_K8_PSTATE_CTRL, etc)

[Keir Fraser <keir@xxxxxxx>]

On 24/02/2012 10:38, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:

>>>> On 24.02.12 at 07:43, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> wrote:
>> # HG changeset patch
>> # User Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
>> # Date 1330065828 18000
>> # Node ID a34b652afb0ca484b7416008c95fd36ffbbea334
>> # Parent  a4d93d0e0df2fafe5b3e2dab3e34799498a875e2
>> traps: AMD PM RDMSRs (MSR_K8_PSTATE_CTRL, etc)
>> 
>> The restriction to read and write the AMD power management MSRs is gated if
>> the
>> domain 0 is the PM domain (so FREQCTL_dom0_kernel is set). But we can
>> relax this restriction and allow the privileged domain to read the MSRs
>> (but not write). This allows the priviliged domain to harvest the power
>> management information (ACPI _PSS states) and send it to the hypervisor.
>> 
>> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
>> 
>> diff -r a4d93d0e0df2 -r a34b652afb0c xen/arch/x86/traps.c
>> --- a/xen/arch/x86/traps.c Wed Feb 22 14:33:24 2012 +0000
>> +++ b/xen/arch/x86/traps.c Fri Feb 24 01:43:48 2012 -0500
>> @@ -2610,7 +2610,7 @@ static int emulate_privileged_op(struct
>>          case MSR_K8_PSTATE7:
>>              if ( boot_cpu_data.x86_vendor != X86_VENDOR_AMD )
>>                  goto fail;
>> -            if ( !is_cpufreq_controller(v->domain) )
>> +            if ( !is_cpufreq_controller(v->domain) && !IS_PRIV(v->domain) )
> 
> As said already in response to your Linux side overview mail, while
> I don't view this as having potential to cause any problems, I also
> don't see the need.
> 
> And then if this indeed is wanted, replacing is_cpufreq_controller()
> by IS_PRIV() rather than adding the latter would seem preferable
> (because of being more strait forward).

Any response to this, Konrad?

 K.

> Jan
> 
>>              {
>>                  regs->eax = regs->edx = 0;
>>                  break;
>> 
>> 
>> 
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> 
> 
> 
> 
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