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


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

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.


Julien Grall

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