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

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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