Re: [Xen-devel] [RFC Design Doc] Add vNVDIMM support for Xen

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 17.03.16 at 14:37, <haozhong.zhang@xxxxxxxxx> wrote:
> On 03/17/16 11:05, Ian Jackson wrote:
>> Jan Beulich writes ("Re: [Xen-devel] [RFC Design Doc] Add vNVDIMM support 
>> for 
> Xen"):
>> > So that again leaves unaddressed the question of what you
>> > imply to do when a guest elects to use such a page as page
>> > table. I'm afraid any attempt of yours to invent something that
>> > is not struct page_info will not be suitable for all possible needs.
>> 
>> It is not clear to me whether this is a realistic thing for a guest to
>> want to do.  Haozhong, maybe you want to consider this aspect.
>>
> 
> For HVM guests, it's themselves responsibility to not grant (e.g. in
> xen-blk/net drivers) a vNVDIMM page containing page tables to others.
> 
> For PV guests (if we add vNVDIMM support for them in future), as I'm
> going to use page_info struct for it, I suppose the current mechanism
> in Xen can handle this case. I'm not familiar with PV memory
> management and have to admit I didn't find the exact code that handles
> the case that a memory page contains the guest page table. Jan, could
> you indicate the code that I can follow to understand what xen does in
> this case?

xen/arch/x86/mm.c has functions like __get_page_type(),
alloc_page_type(), alloc_l[1234]_table(), and mod_l[1234]_entry()
which all participate in this.

Jan


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