Re: [Xen-devel] Re: [PATCH] xen: reduce severity of message about using v1 grant tables.

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2009-12-03 at 20:15 +0000, Jeremy Fitzhardinge wrote: 
> On 12/03/09 04:15, Ian Campbell wrote:
> > I'm experimenting with this:
> >
> > Subject: xen: latch grant-table layout at start of day.
> >
> > It is not possible to switch grant table layout over a save restore
> > since entries setup before with the old layout cannot be torn down under
> > the new layout.
> >   
> 
> Doesn't resume implicitly tear them all down?

Yes, but the devices will try and tear them down again in their resume
handlers. I think the conclusion was (see Steven's last mail) that since
changing gnttab version memsets the array to zero and gnttab_end_*
happen to be safe (by inspection) when used on a zeroed slot it would be
ok.

I think it's just safest to avoid the whole issue, we don't care about
the downgrade case and in the upgrade case the guest isn't going to have
any devices running which need v2 so can just as well stick with v1.

Ian.



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