Re: [Xen-devel] [PATCH V3 1/1] expand x86 arch_shared_info to support >3 level p2m tree

[Juergen Gross <jgross@xxxxxxxx>]

On 09/30/2014 10:53 AM, Jan Beulich wrote:
> > > > On 09.09.14 at 11:58, <"jgross@xxxxxxxx".non-mime.internet> wrote:
> > The x86 struct arch_shared_info field pfn_to_mfn_frame_list_list
> > currently contains the mfn of the top level page frame of the 3 level
> > p2m tree, which is used by the Xen tools during saving and restoring
> > (and live migration) of pv domains. With three levels of the p2m tree
> > it is possible to support up to 512 GB of RAM for a 64 bit pv domain.
> > A 32 bit pv domain can support more, as each memory page can hold 1024
> > instead of 512 entries, leading to a limit of 4 TB. To be able to
> > support more RAM on x86-64 an additional level is to be added.
> >
> > This patch expands struct arch_shared_info with a new p2m tree root
> > and the number of levels of the p2m tree. The new information is
> > indicated by the domain to be valid by storing ~0UL into
> > pfn_to_mfn_frame_list_list (this should be done only if more than
> > three levels are needed, of course).
> >
> > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> Still having this in my to-be-committed-or-otherwise list, David -
> you had reservations here. Did they get addressed by JÃrgen?
> Is there any alternative proposal? Or are we setting this aside
> until after 4.5?
David had the alternative proposal to use a virtual mapped linear
mfn_list with the tools doing the translation as needed. I'm just
trying to do this, so please ignore my patch.


Juergen


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