Re: [Xen-devel] [RFC Design Doc v2] Add vNVDIMM support for Xen

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, Aug 04, 2016 at 05:35:12PM +0800, Haozhong Zhang wrote:
> On 08/04/16 03:25, Jan Beulich wrote:
> > >>> On 04.08.16 at 10:52, <haozhong.zhang@xxxxxxxxx> wrote:
> > > On 08/03/16 17:25, Konrad Rzeszutek Wilk wrote:
> > >> Anyhow, wouldn't this 'sizeof(struct page_info)' depend on the ndctl
> > >> tool and what version was used to create this? What if one version
> > >> used 32-bytes for a PAGE, while another used 64-bytes for a PAGE too?
> > >> It would be a bit of catching up .. wait, this same problem MUST
> > >> be with Linux? How does it deal with this?
> > > 
> > > Good question. Linux chooses a size (64 bytes) larger than its current
> > > sizeof(struct page) (40 bytes). We may also do in the same way,
> > > e.g. 32 bytes vs. 64 bytes?
> > 
> > I don't understand this: These structures aren't meant to be
> > persistent, so their size shouldn't matter?
> > 
> 
> But the size of the reserved area is persistent. If the size of struct
> page_info increases in future versions, the reserved area which is
> just enough for old version struct page_info would not be enough for
> the new version.

Exactly!!

Thanks!

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