Re: [Xen-devel] RFC: making the PVH 64bit ABI as stableo

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 3 Jun 2015, Jan Beulich wrote:
> >>> On 03.06.15 at 12:02, <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> > On Tue, 2 Jun 2015, Andrew Cooper wrote:
> >> With my x86 maintainer hat on, the following is an absolute minimum set
> >> of prerequisite for PVH.
> >> 
> >> * 32bit support
> > 
> > Could you please explain why 32bit is important to get PVH out of tech
> > preview? I don't see 32 bit OSes as an important use case. Maybe there
> > is more behind it that I cannot see.
> 
> The primary reason was named before: 32-bit support will likely
> end up changing the way 64-bit guests get launched.

I would rather have 64-bit only PVH, then no PVH. No PVH is what we have
today.


> >> * AMD support
> > 
> > Given that it is pretty difficult for any AMD related changes to affect
> > the interface, why is this item in the list of things needed to get out
> > of experimental?
> 
> Because we cannot rule out that adding SVM support may require
> interface changes. And even if we promoted it to tech preview,
> the interface would still not be frozen.

Without a "frozen" interface, the thing is unusable. I would rather have
an Intel only, DomU only, 64-bit only PVH, than no PVH at all, that is
the current state of things, which is unlikely to change in the short
and medium terms.

Nobody replied with a timeline for these two features yet, but from the
look of things, if we maintain the current pace, I would guess we are
looking at late 2017. In my option that is too late and would rather rip
PVH off.


> Apart from that (and I also said so on the hackathon session, just
> like you considering to rip the whole thing out if it doesn't make
> any progress) already during initial patch review I was hesitant to
> accept changes with so many loose ends; I accepted them on the
> basis that they would get dealt with in a timely manner, which
> didn't happen, and which leaves us in this sad, half working (or
> should I say half broken) state.

I completely agree.

Also it would be nice if any discussions at the hackathon, or anywhere
else, were written down and sent to the list. Otherwise people like me,
that didn't attend, will just think of them as rumors.

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