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

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Wed, Jun 28, 2017 at 05:20:38PM +0100, Andrew Cooper wrote:
> On 28/06/17 17:14, Marek Marczykowski-Górecki wrote:
> > On Wed, Jun 28, 2017 at 11:16:33AM +0100, Andrew Cooper wrote:
> >> 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...
> > I don't have opinion on either approach here, but the current state is
> > clearly wrong. You've got two versions of the patch, choose one ;)
> >
> 
> I'd prefer this version of the patch, so it doesn't suddenly remove a
> piece of libxl API, but it is up to Wei / Ian at the end of the day.

Keeping it is better. It doesn't really make any difference to the guest
but some tools might complain if we remove it.

> 
> One option which was being discussed in the context of my CPUID (part 3)
> work was to automatically this list of keywords.
> 

"generate"?

And yes, I fully support this work. ;-)

> ~Andrew

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