Re: [Xen-devel] [PATCH 4/4] hvmloader: add support to load extra ACPI tables from qemu

[Haozhong Zhang <haozhong.zhang@xxxxxxxxx>]

On 01/26/16 14:32, Konrad Rzeszutek Wilk wrote:
> On Tue, Jan 26, 2016 at 09:34:13AM -0700, Jan Beulich wrote:
> > >>> On 26.01.16 at 16:57, <haozhong.zhang@xxxxxxxxx> wrote:
> > > On 01/26/16 08:37, Jan Beulich wrote:
> > >> >>> On 26.01.16 at 15:44, <konrad.wilk@xxxxxxxxxx> wrote:
> > >> >>  Last year at Linux Plumbers Conference I attended a session dedicated
> > >> >> to NVDIMM support. I asked the very same question and the INTEL guy
> > >> >> there told me there is indeed something like a partition table meant
> > >> >> to describe the layout of the memory areas and their contents.
> > >> > 
> > >> > It is described in details at pmem.io, look at  Documents, see
> > >> > http://pmem.io/documents/NVDIMM_Namespace_Spec.pdf see Namespaces 
> > >> > section.
> > >> 
> > >> Well, that's about how PMEM and PBLK ranges get marked, but not
> > >> about how use of the space inside a PMEM range is coordinated.
> > >>
> > > 
> > > How a NVDIMM is partitioned into pmem and pblk is described by ACPI NFIT 
> > > table.
> > > Namespace to pmem is something like partition table to disk.
> > 
> > But I'm talking about sub-dividing the space inside an individual
> > PMEM range.
> 
> The namespaces are it.
>

Because only one persistent memory namespace is allowed for an
individual pmem, namespace can not be used to sub-divide.

> Once you have done them you can mount the PMEM range under say /dev/pmem0
> and then put a filesystem on it (ext4, xfs) - and enable DAX support.
> The DAX just means that the FS will bypass the page cache and write directly
> to the virtual address.
> 
> then one can create giant 'dd' images on this filesystem and pass it
> to QEMU to .. expose as NVDIMM to the guest. Because it is a file - the blocks
> (or MFNs) for the contents of the file are most certainly discontingous.
>

Though the 'dd' image may occupy discontingous MFNs on host pmem, we can map 
them
to contiguous guest PFNs.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel