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

[Haozhong Zhang <haozhong.zhang@xxxxxxxxx>]

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?

Thanks,
Haozhong

> If you can come up with an argument why it is OK to simply not permit
> this, then maybe the recordkeeping requirements can be relaxed ?
> 
> Ian.

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