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

[Paul Durrant <xadimgnik@xxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich <jbeulich@xxxxxxxx>
> Sent: 06 March 2020 13:36
> To: Paul Durrant <xadimgnik@xxxxxxxxx>
> Cc: sstabellini@xxxxxxxxxx; julien@xxxxxxx; Volodymyr_Babchuk@xxxxxxxx; 
> wl@xxxxxxx;
> konrad.wilk@xxxxxxxxxx; andrew.cooper3@xxxxxxxxxx; ian.jackson@xxxxxxxxxxxxx;
> george.dunlap@xxxxxxxxxx; xen-devel@xxxxxxxxxxxxxxxxxxxx; 'David Woodhouse' 
> <dwmw2@xxxxxxxxxxxxx>
> Subject: Re: [PATCH 2/2] domain: use PGC_extra domheap page for shared_info
> 
> On 06.03.2020 14:26, Paul Durrant wrote:
> >> From: Xen-devel <xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf Of Jan 
> >> Beulich
> >> Sent: 06 March 2020 13:24
> >>
> >> On 06.03.2020 14:13, Paul Durrant wrote:
> >>> 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.
> >>
> >> Following David's various replies - instead of going this route of
> >> replacing the sharing of xenheap pages by different logic, the
> >> same ought to be achievable by making the backing allocations come
> >> from the correct pool?
> >>
> >
> > I still prefer the simplification of not having to clean up the
> > shared xenheap page list in domain_kill() so IMO it is still worth
> > it for that alone.
> 
> I don't see anything very special with the cleaning up in
> domain_kill() / domain_relinquish_resources(). What I'd view as
> more desirable in this regard is the general fact of needing
> two lists. But you realize there's a downside to this as well?
> dump_pageframe_info() will reliably show _all_ Xen heap pages
> associated with a domain, but it will only ever show up to 10
> pages on ->page_list for a domain that's not already being
> cleaned up.

That's not much of a downside though I don't think. The xenheap (or PGC_extra 
domheap pages) are 'special' and so info about them ought to be available via 
an alternate dump function anyway (and if not already, it can be added).

  Paul

> 
> Jan


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