Re: [Xen-devel] [RFC KERNEL PATCH 0/2] Add Dom0 NVDIMM support for Xen

From: Jan Beulich
Date: Tue Oct 11 2016 - 09:08:48 EST

>>> Andrew Cooper <andrew.cooper3@xxxxxxxxxx> 10/10/16 6:44 PM >>>
>On 10/10/16 01:35, Haozhong Zhang wrote:
>> Xen hypervisor needs assistance from Dom0 Linux kernel for following tasks:
>> 1) Reserve an area on NVDIMM devices for Xen hypervisor to place
>> memory management data structures, i.e. frame table and M2P table.
>> 2) Report SPA ranges of NVDIMM devices and the reserved area to Xen
>> hypervisor.
>However, I can't see any justification for 1). Dom0 should not be
>involved in Xen's management of its own frame table and m2p. The mfns
>making up the pmem/pblk regions should be treated just like any other
>MMIO regions, and be handed wholesale to dom0 by default.

That precludes the use as RAM extension, and I thought earlier rounds of
discussion had got everyone in agreement that at least for the pmem case
we will need some control data in Xen.