Re: [PATCH v3 4/4] spapr: Forbid nested KVM-HV in pre-power9 compat mode

[David Gibson]

On Mon, Jun 15, 2020 at 11:20:31AM +0200, Greg Kurz wrote:
> On Sat, 13 Jun 2020 17:18:04 +1000
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > On Thu, Jun 11, 2020 at 03:40:33PM +0200, Greg Kurz wrote:
> > > Nested KVM-HV only works on POWER9.
> > > 
> > > Signed-off-by: Greg Kurz <groug@kaod.org>
> > > Reviewed-by: Laurent Vivier <lvivier@redhat.com>
> > 
> > Hrm.  I have mixed feelings about this.  It does bring forward an
> > error that we'd otherwise only discover when we try to load the kvm
> > module in the guest.
> > 
> > On the other hand, it's kind of a layering violation - really it's
> > KVM's business to report what it can and can't do, rather than having
> > qemu anticipate it.
> > 
> 
> Agreed and it seems that we can probably get KVM to report that
> already. I'll have closer look.
> 
> > Allowing POWER8 compat for an L2 is something we hope to have in the
> > fairly near future.
> 
> Ok but I guess we don't want to start an L2 in compat POWER8 mode
> with cap-nested-hv=on, do we ?

Sorry, "L2" was misleading, I really mean L<max>.  Setting
cap-nested-hv kind of implies there's a L<at least one more> which
contradicts that.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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