Re: [Xen-devel] HVMLite / PVHv2 - using x86 EFI boot entry

[Luis R. Rodriguez]

On Wed, Apr 13, 2016 at 03:02:26PM -0400, Konrad Rzeszutek Wilk wrote:
> On Wed, Apr 13, 2016 at 08:50:10PM +0200, Luis R. Rodriguez wrote:
> > On Wed, Apr 13, 2016 at 11:54:29AM +0200, Roger Pau Monné wrote:
> > > On Fri, Apr 08, 2016 at 11:58:54PM +0200, Luis R. Rodriguez wrote:
> > > > OK thanks for the clarification -- still no custom entries for Xen!
> > > > We should strive for that, at the very least.
> > > > 
> > > > You do have a point about the legacy stuff. There are two options there:
> > > > 
> > > >   * Fold legacy support under HVMLite -- which seems to be what we
> > > >     currently want to do (we should evaluate the implications and
> > > >     requirements here for that); or
> > > 
> > > I'm not following here. What does it mean to fold legacy support under 
> > > HVMlite? HVMlite doesn't have any legacy hardware, and that's the issue when 
> > > it comes to using native Linux entry points. Linux might expect some legacy 
> > > PC hardware to be always present, which is not true for HVMlite.
> > > 
> > > Could you please clarify this point?
> > 
> > It seems there is a confusion on terms used. By folding legacy support under
> > HVMLite I meant folding legacy PV path (classic PV with PV interfaces) under
> > HVMlite.
> 
> Ewww.

Probably a confusion again on terms, by the above I meant to say what you seem
to be indicating below, which is to keep old PV guest support with PV interfaces
using a new shiny entry.

Or are we really going to nuke full support for old PV guests ?

> > I got the impression that if we wanted to remove the old PV path we had to see
> > if we can address old classic PV x86 guests through HVMlite, otherwise we'd
> > have to live with the old PV path for the long term.
> 
> No. We need to deprecate the PV paths - and the agreement we hammered out
> with the x86 maintainers was that once PVH/HVMLite is stable the clock
> would start ticking on PV (pvops) life. All the big users of PV Linux
> were told in persons to prep them for this.

That's nice. *How* that is done is what we are determining here.

> Keep in mind that this is not for deleting of support in hypervisor for
> PV hypercalls - meaning you would still be able to run say 2.6.18 RHEL5
> in years to come. It is just that Linux v6.1 won't have any more PV paths
> and can only run in HVM or PVH/HVMLite mode under Xen.

Sure.

  Luis