Messages in this thread | | | From | Dan Williams <> | Date | Tue, 11 Oct 2016 08:53:33 -0700 | Subject | Re: [Xen-devel] [RFC KERNEL PATCH 0/2] Add Dom0 NVDIMM support for Xen |
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On Tue, Oct 11, 2016 at 6:08 AM, Jan Beulich <jbeulich@suse.com> wrote: >>>> Andrew Cooper <andrew.cooper3@citrix.com> 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.
The missing piece for me is why this reservation for control data needs to be done in the libnvdimm core? I would expect that any dax capable file could be mapped and made available to a guest. This includes /dev/ramX devices that are dax capable, but are external to the libnvdimm sub-system.
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