Re: [Xen-devel] [PATCH 3/6] X86: Disable PCID/INVPCID for dom0

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 27.11.11 at 11:16, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> wrote:
> Jan Beulich wrote:
>>>>> On 24.11.11 at 16:53, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> wrote:
>>> This patch disable PCID/INVPCID for dom0.
>> 
>> Do we really need to disable it, rather than making it work?
>> Conceptually the feature seems usable, and the instruction would
>> need replacement by a hypercall anyway (just like invlpg).
> 
> It's a design choice.
> Exposing PCID/INVPCID to pv would involve some additional task, like 
> coordinated PCID allocation algorithm, or change vmm vcpu context swich, 
> which would make it complex. However, exposing PCID/INVPCID to pv has not 
> obvious benefit or even result in performance regression.

Would you mind elaborating on that statement?

Jan

> So we choose to disable PCID/INVPCID to pv.
> 
> Thanks,
> Jinsong



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