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

To: Jan Beulich <JBeulich@xxxxxxxxxx>, Keir Fraser <keir@xxxxxxx>
Subject: RE: [Xen-devel] [PATCH] Allow dom0 to write MSR IA32_ENERGY_PERF_BIAS
From: "Wei, Gang" <gang.wei@xxxxxxxxx>
Date: Wed, 5 Jan 2011 16:55:23 +0800
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Thread-topic: [Xen-devel] [PATCH] Allow dom0 to write MSR IA32_ENERGY_PERF_BIAS
Jan Beulich wrote on 2011-01-05:
>>>> On 05.01.11 at 09:22, Keir Fraser <keir@xxxxxxx> wrote:
>> 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).

Ok, I accept such kind of usages. So how about simply check in my patch and do 
remove these restrictions in your following patches?

>>>> 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.
> They aren't outright unnecessary I'd say, they just need some relaxing
> (as the code makes sense also when the vCPU is constrained to a single
> pCPU). That's the change I'm going to send shortly.


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