Re: [Xen-devel] [PATCH] Allow dom0 to write MSR IA32_ENERGY_PERF

To:	Jan Beulich <JBeulich@xxxxxxxxxx>, Gang Wei <gang.wei@xxxxxxxxx>
Subject:	Re: [Xen-devel] [PATCH] Allow dom0 to write MSR IA32_ENERGY_PERF_BIAS
From:	Keir Fraser <keir@xxxxxxx>
Date:	Wed, 05 Jan 2011 08:22:46 +0000
Cc:	"xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
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Thread-topic:	[Xen-devel] [PATCH] Allow dom0 to write MSR IA32_ENERGY_PERF_BIAS
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On 05/01/2011 08:17, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

>>>> On 05.01.11 at 09:13, Keir Fraser <keir.fraser@xxxxxxxxxxxxx> wrote:
>> On 05/01/2011 07:59, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:
>> 
>>>>> Why would you allow this only if Dom0 has its vcpus pinned?
>>>> 
>>>> It is meaningless if dom0 can't control all pcpus exactly. Only in case of
>>>> dom0 vcpus pinned, it makes sense.
>>> 
>>> Disagree. The user mode tool could set its own affinity (virtual and
>>> physical) and then issue the MSR write. Please don't enforce
>>> restrictions where not really needed (I actually suppose that the
>>> restriction should be removed for MSR_IA32_THERM_CONTROL too).
>> 
>> If so, it deserves a separate patch to strip out *all* the is_pinned checks
>> at the same time.
> 
> You certainly don't mean *all*, but yes, I'm intending to submit such
> a patch.

The ones in x86/traps.c (WRMSR emulation) and x86/domain.c
(VCPUOP_get_physid) are both unnecessary, at least.

 -- Keir

> Jan
> 
> 
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Re: [Xen-devel] [PATCH] Allow dom0 to write MSR IA32_ENERGY_PERF_BIAS