Re: [Xen-devel] [PATCH 2/2] domain: use PGC_extra domheap page for shared_info

[Julien Grall <julien@xxxxxxx>]

(+David)

On 26/02/2020 15:23, Jan Beulich wrote:
> On 26.02.2020 15:05, Durrant, Paul wrote:
> > > From: Jan Beulich <jbeulich@xxxxxxxx>
> > > Sent: 26 February 2020 13:58
> > >
> > > On 25.02.2020 10:53, Paul Durrant wrote:
> > > > There's no particular reason shared_info need use a xenheap page. It's
> > > > only purpose is to be mapped by the guest so use a PGC_extra domheap
> > > page
> > > > instead.
> > > Since the cover letter also doesn't give any background - is there a
> > > problem with the current arrangements? Are there any further plans
> > > depending on this being changed? Or is this simply "let's do it
> > > because now we can"?
> > The general direction is to get rid of shared xenheap pages. Knowing
> > that a xenheap page is not shared with a guest makes dealing with
> > live update much easier,
> I may not be seeing enough of the overall picture, but it would seem
> to me that the special treatment of shared Xen heap pages would then
> be replaced by special treatment of PGC_extra ones.
I have been working on Liveupdate for the past couple months and I don't 
 really see how this is going to make liveupdate easier. We will still 
need to save the extra flags and extra records for each subsystem using 
them (e.g grant-tables).
I have CCed David to see if he has a different opinion.

Cheers,

--
Julien Grall

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