HEADS UP: merged PVHv2 support and future plans

[Roger Pau Monné]

On Thu, Jul 19, 2018 at 02:03:00PM +0200, Miroslav Lachman wrote:
> Roger Pau Monné wrote on 2018/07/19 11:04:
> > Hello,
> > 
> > Today I've merged PVHv2 support into FreeBSD, allowing FreeBSD to be
> > used as a PVHv2 DomU and Dom0. While it's not a huge set of changes,
> > I would *really* appreciate if people could test the code starting
> > from r336474 (or any later changeset).
> > 
> > I expect there's going to be some confusion with PVHv1 vs PVHv2, so I
> > will try to clarify this now. PVHv1 was introduced ~4 years ago, and
> > at the time it seemed like a good way to move forward, allowing Xen to
> > rely more on hardware virtualization. Later on, we sadly discovered
> > that PVHv1 was still too similar to classic PV, and didn't allow Xen
> > to make use of all the possible hardware virtualization extensions, so
> > PVHv2 was introduced ~2 years ago as a replacement for PVHv1. PVHv2
> > ABI however is not compatible with PVHv1, which means that different
> > entry points and interfaces must be used to interact with the
> > hypervisor.
> > 
> > After introducing PVHv2 PVHv1 was deprecated and PVHv1 has been
> > removed from the hypervisor in recent versions, that's why the Xen
> > ports package is still stuck with Xen 4.7, because later versions
> > removed PVHv1 support. With the addition of PVHv2 to FreeBSD the port
> > can be updated to newer Xen versions and we can move forward.
> > 
> > There will be issues however, as newer versions of Xen won't have
> > support for PVHv1. My plan is the following in order to try to make
> > this less painful for users:
> > 
> >   - Wait until FreeBSD 12 is released, which will contain PVHv1 and
> >     PVHv2 support.
> >   - Once FreeBSD 12 has been released, update the Xen port to the
> >     latest version.
> 
> What about creating new port as xen410 (for version 4.10) or repocopy of the
> old one to xen47 to allow coexist of two different versions in the ports
> tree and allow user to choose the right one for their OS version?

I wondered about that, I will try to do it, but I have to admit my
time is quite limited and I'm not sure I will be able to keep both up
to data.

Thanks, Roger.