Re: [Xen-devel] [PATCH 06/10] x86/cpuid: Handle leaf 0x6 in guest_cpuid()

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 21/02/17 17:40, Andrew Cooper wrote:
> On 21/02/17 17:25, Jan Beulich wrote:
>>>>> On 20.02.17 at 12:00, <andrew.cooper3@xxxxxxxxxx> wrote:
>>> The thermal/performance leaf was previously hidden from HVM guests, but 
>>> fully
>>> visible to PV guests.  Most of the leaf refers to MSR availability, and 
>>> there
>>> is nothing an unprivileged PV guest can do with the information, so hide the
>>> leaf entirely.
>>>
>>> The PV MSR handling logic as minimal support for some thermal/perf 
>>> operations
>> ... has ...
>>
>>> from the hardware domain, so leak through the implemented subset of 
>>> features.
>> Does it make sense to continue to special case PV hwdom here?
> Being able to play with these MSRs will be actively wrong for HVM
> context.  It is already fairly wrong for PV context, as nothing prevents
> you being rescheduled across pcpus while in the middle of a read/write
> cycle on the MSRs.
>
>> Should there perhaps be at least a fixme note?
> One way or another, we have to invest some different mechanism of
> providing real hardware details to the hardware domain which don't
> collide with their vcpus.

s/invest/invent/.  Sorry for the confusion.

~Andrew

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