Re: [Xen-devel] [RFC PATCH] page_alloc: use first half of higher order chunks when halving

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.04.14 at 16:40, <konrad.wilk@xxxxxxxxxx> wrote:
> That was OK, but the M2P lookup table was not too thrilled with this.
> Perhaps I should have used another hypercall to re-arrange the M2P?
> I think I did try 'XENMEM_exchange' but that is not the right call either.

Yeah, that's allocating new pages in exchange for your old ones. Not
really what you want.

> Perhaps I should use XENMEM_remove_from_physmap/XENMEM_add_to_physmap
> combo ?

A pair of MMU_MACHPHYS_UPDATE operations would seem to be the
right way of doing this (along with respective kernel internal accounting
like set_phys_to_machine(), and perhaps a pair of update_va_mapping
operations if the 1:1 map is already in place at that time, and you care
about which page contents appears at which virtual address).

Jan


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