Re: [Xen-devel] Restoring FPU exception state

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 18.02.16 at 09:41, <Paul.Durrant@xxxxxxxxxx> wrote:
>>  -----Original Message-----
>> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>> Sent: 18 February 2016 08:16
>> To: Kevin Tian
>> Cc: Andrew Cooper; David Vrabel; Paul Durrant; Feng Wu; xen-devel
>> Subject: RE: Restoring FPU exception state
>> 
>> >>> On 18.02.16 at 07:30, <kevin.tian@xxxxxxxxx> wrote:
>> > Interesting. Let me also have a check internally whether there is other
>> > architectural alternative. BTW, not quite related. Could I think finally
>> > Xen may allow user to specify OS type as a general per-domain control,
>> > and then Xen can do free optimizations underlying based on that type?
>> > I don't expect we want to expose raw FPU related per-domain control
>> > since it's difficult for users to correctly set it up...
>> 
>> So what if then, with us implying some kind of workaround here
>> from the OS type, someone set the OS type to Windows, and
>> subsequently MS decided to fix their issue?
> 
> We already get full OS version information from Windows via the 
> VIRIDIAN_MSR_GUEST_OS_ID MSR so it would be quite straightforward to work 
> around the issue for all Windows at the moment and then make the check more 
> specific if Microsoft choose to avoid the problem by some other means.

That's only if "viridian=1" in the guest config, isn't it? Plus - how would
we know MS chose to fix their apparent issue?

Jan


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