Re: [Qemu-devel] [RFC QEMU PATCH v4 00/10] Implement vNVDIMM for Xen HVM guest

[Haozhong Zhang]

On 02/27/18 17:22 +0000, Anthony PERARD wrote:
> On Thu, Dec 07, 2017 at 06:18:02PM +0800, Haozhong Zhang wrote:
> > This is the QEMU part patches that works with the associated Xen
> > patches to enable vNVDIMM support for Xen HVM domains. Xen relies on
> > QEMU to build guest NFIT and NVDIMM namespace devices, and allocate
> > guest address space for vNVDIMM devices.
> 
> I've got other question, and maybe possible improvements.
> 
> When QEMU build the ACPI tables, it also initialize some MemoryRegion,
> which use more guest memory. Do you know if those regions are used with
> your patch series on Xen?

Yes, that's why dm_acpi_size is introduced.

> Otherwise, we could try to avoid their
> creation with this:
> In xenfv_machine_options()
> m->rom_file_has_mr = false;
> (setting this in xen_hvm_init() would probably be better, but I havn't
> try)

If my memory is correct, simply setting rom_file_has_mr to false does
not work (though I cannot remind the exact reason). I'll have a look
as the code to refresh my memory.

Haozhong

> 
> If this is possible, libxl would not need to allocate more memory for
> the guest (dm_acpi_size).
> 
> -- 
> Anthony PERARD