Re: [Xen-devel] [PATCH 0/2] xen: Switch to virtual mapped linear p2m list

From: Juergen Gross
Date: Tue Oct 28 2014 - 09:03:14 EST


On 10/28/2014 01:46 PM, Andrew Cooper wrote:
On 28/10/14 12:44, David Vrabel wrote:
On 28/10/14 12:42, Andrew Cooper wrote:
On 28/10/14 12:39, David Vrabel wrote:
On 28/10/14 12:07, Juergen Gross wrote:
Okay, back to the original question: is the (up to) 64 MB virtual
mapping of the p2m list on 32-bit pv domains a problem or not?
I think up-to 64 MiB of vmalloc area is fine. The vmalloc space can be
increased with a command line option in the unlikely event that there
are domUs that would be affected.

If yes, the virtual mapped linear p2m list could still be used on
64 bit domains, paving the way for support of more than 512 GB of
domain memory. OTOH having to keep the p2m tree coding alive isn't
my favorite solution...
Having to keep both the tree and linear p2m code would be awful. Let's
not do this!

David
How is the toolstack expected to find and mutate this p2m on migrate?
The toolstack does not use guest pagetables.
The p2m code maintains two trees. One for use by the guest and one for
use by the toolstack. This series replaces the first tree with the
linear array (at least that's how I understand it -- I've not reviewed
the series in detail yet).

Ah - fine (if that is how it works).

That's the plan, yes.


Juergen

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