Re: [PATCH] x86/Intel: insert Ice Lake and Comet Lake model numbers

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Fri, Jun 05, 2020 at 10:54:22AM +0200, Jan Beulich wrote:
> On 05.06.2020 10:46, Roger Pau Monné wrote:
> > On Fri, Jun 05, 2020 at 10:10:01AM +0200, Jan Beulich wrote:
> >> On 05.06.2020 10:02, Roger Pau Monné wrote:
> >>> On Fri, Jun 05, 2020 at 09:51:09AM +0200, Jan Beulich wrote:
> >>>> Both match prior generation processors as far as LBR and C-state MSRs
> >>>> go (SDM rev 072) as well as applicability of the if_pschange_mc erratum
> >>>> (recent spec updates).
> >>>>
> >>>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> >>>> ---
> >>>> Such changes having been subject to backporting in the past, this
> >>>> change may want considering for 4.14.
> >>>> ---
> >>>> I'm leaving alone spec_ctrl.c, albeit there's a scary looking erratum
> >>>> for Ice Lake indicating that MDS_NO may wrongly be set. But this is
> >>>> apparently addressed by ucode update, so we may not need to deal with
> >>>> it in software.
> >>>>
> >>>> --- a/xen/arch/x86/acpi/cpu_idle.c
> >>>> +++ b/xen/arch/x86/acpi/cpu_idle.c
> >>>
> >>> What about mwait-idle? I guess we pick that from Linux and no patch
> >>> has been added so far?
> >>
> >> Correct. I've looked at recent history there, and I'm uncertain they'll
> >> add further models there. They look to prefer to use ACPI _CST now again
> >> with, as it seems, not overly much of a difference to the ACPI driver
> >> (which, if we were to follow, I'd rather see us integrate there).
> > 
> > Urg, OK, that's a shame as using mwait-idle was IMO better from a Xen
> > PoV as we didn't rely on dom0 in order to discover C states. I wonder
> > if we could continue to update mwait-idle on our own for newer models.
> 
> This would be nice indeed, but would require Intel to provide us with
> the necessary data.
> 
> > FWIW, wikichip also lists 6c and 6a [0] as Ice Lake Server model versions,
> > but I'm not sure if this has been confirmed in any way?
> 
> SDM vol 4 confirms this, but mentions the two model numbers exclusively
> in the table matching signatures to model names ("Future Intel Xeon
> processors based on Ice Lake microarchitecture"). Without there being an
> actual table for these I don't think we should "speculatively" add the
> numbers anywhere.

Ack.

Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Thanks.