Re: [Xen-devel] [PATCH 0/4] add support for vNVDIMM

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 20 Jan 2016, Tian, Kevin wrote:
> > From: Zhang, Haozhong
> > Sent: Tuesday, December 29, 2015 7:32 PM
> > 
> > This patch series is the Xen part patch to provide virtual NVDIMM to
> > guest. The corresponding QEMU patch series is sent separately with the
> > title "[PATCH 0/2] add vNVDIMM support for Xen".
> > 
> > * Background
> > 
> >  NVDIMM (Non-Volatile Dual In-line Memory Module) is going to be
> >  supported on Intel's platform. NVDIMM devices are discovered via ACPI
> >  and configured by _DSM method of NVDIMM device in ACPI. Some
> >  documents can be found at
> >  [1] ACPI 6: http://www.uefi.org/sites/default/files/resources/ACPI_6.0.pdf
> >  [2] NVDIMM Namespace: http://pmem.io/documents/NVDIMM_Namespace_Spec.pdf
> >  [3] DSM Interface Example:
> > http://pmem.io/documents/NVDIMM_DSM_Interface_Example.pdf
> >  [4] Driver Writer's Guide:
> > http://pmem.io/documents/NVDIMM_Driver_Writers_Guide.pdf
> > 
> >  The upstream QEMU (commits 5c42eef ~ 70d1fb9) has added support to
> >  provide virtual NVDIMM in PMEM mode, in which NVDIMM devices are
> >  mapped into CPU's address space and are accessed via normal memory
> >  read/write and three special instructions (clflushopt/clwb/pcommit).
> > 
> >  This patch series and the corresponding QEMU patch series enable Xen
> >  to provide vNVDIMM devices to HVM domains.
> > 
> > * Design
> > 
> >  Supporting vNVDIMM in PMEM mode has three requirements.
> > 
> 
> Although this design is about vNVDIMM, some background of how pNVDIMM
> is managed in Xen would be helpful to understand the whole design since
> in PMEM mode you need map pNVDIMM into GFN addr space so there's
> a matter of how pNVDIMM is allocated.

Yes, some background would be very helpful. Given that there are so many
moving parts on this (Xen, the Dom0 kernel, QEMU, hvmloader, libxl)
I suggest that we start with a design document for this feature.

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