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

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Apr 13, 2016 at 09:14:08PM +0200, Luis R. Rodriguez wrote:
> 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 ?

Please re-read my email. The hypervisor is not going to nuke it. Linux
will stop using them - and hence the pvops will be obsolete.
> 
> > > 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.

What is being discussed is how PVH/HVMLite is suppose to bootup.
Or the merits of different bootup paths.

Unless you are saying that you want to be the maintainer of pvops
and want to extend the life of pvops in Linux and are trying to make
it work under HVMLite?

> 
> > 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

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