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

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

On Wed, Apr 13, 2016 at 10:01:18PM +0200, Luis R. Rodriguez wrote:
> On Wed, Apr 13, 2016 at 03:22:23PM -0400, Konrad Rzeszutek Wilk wrote:
> > 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 meant remove old PV guests support from Linux. You made it crystal clear
> that the hypervisor will keep legacy PV support.
> 
> Are we going to remove old PV guest support from Linux upstream long term ?

Yes!
> If so then HVMLite design need not be concerned with supporting legacy crap.

Exactly.
> 
> > > > > 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.
> 
> That's part of it...
> 
> > 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?
> 
> Huh? If you look at pvops commits you'll see I've been responsible for
> most of the pvops removal already, my ongoing patches should show that
> my goal is to streamline this further.
> 
> I want to clarify now then what our exist path is, do we need to care
> about legacy crap ?

exist? Existing?

And by 'legacy crap' you mean 'pvops' - then the answer is no.

The big existing use-case of pvops is to boot Linux as initial domain.
If we can swap it over to PVH/HVMLite then that frees us from having to
use pvops.

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