Re: [Xen-devel] [PATCHv1] xen/balloon: disable memory hotplug in PV guests

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 03/10/2015 07:40 AM, David Vrabel wrote:
> On 09/03/15 14:10, David Vrabel wrote:
> > Memory hotplug doesn't work with PV guests because:
> >
> >    a) The p2m cannot be expanded to cover the new sections.
> Broken by 054954eb051f35e74b75a566a96fe756015352c8 (xen: switch to
> linear virtual mapped sparse p2m list).
>
> This one would be non-trivial to fix.  We'd need a sparse set of
> vm_area's for the p2m or similar.
>
> >    b) add_memory() builds page tables for the new sections which means
> >       the new pages must have valid p2m entries (or a BUG occurs).
> After some more testing this appears to be broken by:
>
> 25b884a83d487fd62c3de7ac1ab5549979188482 (x86/xen: set regions above the
> end of RAM as 1:1) included 3.16.
>
> This one can be trivially fixed by setting the new sections in the p2m
> to INVALID_P2M_ENTRY before calling add_memory().
Have you tried 3.17? As I said yesterday, it worked for me (with 4.4 Xen).

-boris


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