Re: [Xen-devel] [PATCH 2/2] libxl: fix osvm cpuid flag

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 28/06/17 07:09, Jan Beulich wrote:
>>>> Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx> 06/28/17 3:09 
>>>> AM >>>
>> It's bit 9 not 10 (which is ibs).
> Indeed, but shouldn't it rather be removed? We don't expose it from the
> hypervisor at all anymore:
>
> XEN_CPUFEATURE(OSVW,          3*32+ 9) /*   OS Visible Workaround */
>
> (note the absence of any marker character immediately inside the comment).

I don't believe we have ever actually offered OSVW to guests, despite
the pretence of being able to.  ISTR it was always clobbered before
being given to a guest.

Having said that, we should be advertising OSVW.  It's entire purpose is
to tell the OS that there is something it can do to manually work round
a specific erratum.  OTOH, making this migrate safe is liable to be very
complicated...

~Andrew

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