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

[Paul Durrant <xadimgnik@xxxxxxxxx>]

> -----Original Message-----
> From: Xen-devel <xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf Of Jan 
> Beulich
> Sent: 06 March 2020 13:10
> To: David Woodhouse <dwmw2@xxxxxxxxxxxxx>; Durrant, Paul 
> <pdurrant@xxxxxxxxxxxx>
> Cc: sstabellini@xxxxxxxxxx; julien@xxxxxxx; wl@xxxxxxx; 
> konrad.wilk@xxxxxxxxxx;
> andrew.cooper3@xxxxxxxxxx; ian.jackson@xxxxxxxxxxxxx; 
> george.dunlap@xxxxxxxxxx; xen-
> devel@xxxxxxxxxxxxxxxxxxxx; Volodymyr_Babchuk@xxxxxxxx
> Subject: Re: [Xen-devel] [PATCH 2/2] domain: use PGC_extra domheap page for 
> shared_info
> 
> On 06.03.2020 13:57, David Woodhouse wrote:
> > On Fri, 2020-03-06 at 13:36 +0100, Jan Beulich wrote:
> >> And of course this means you're intending to (at least
> >> partially) resurrect the distinction between domheap and xenheap,
> >> which isn't said anywhere in Paul's series, I don't think.
> >
> > Right. Secret hiding makes the distinction (xenheap is mapped, domheap
> > is not) mostly go away. We are talking about restoring *a* distinction
> > between one type of page (Xen ephemeral pages which don't need to be
> > preserved over live update) and another (must be preserved), but
> > whether that should still be called "xenheap" vs. "domheap", despite
> > the massive parallels, isn't entirely clear.
> >
> >>  If this
> >> is a sufficiently correct understanding of mine, then on one hand
> >> I start seeing the point of the conversion Paul wants to make, but
> >> otoh this then feels a little like making the 2nd step before the
> >> 1st.
> >
> >
> > What would you suggest is the first step?
> 
> Establishing of what the new separation rule and mechanism is going
> to be (no matter how the two resulting pieces are going to be
> named).
> 

Would you be ok with a comment to that effect? My aim is to make the separation 
abundantly obvious by getting rid of shared xenheap pages (for non-system 
domains at least) but I can't do that before converting shared_info and grant 
shared/status frames to domheap.

  Paul

> Jan
> 
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