Re: [PATCH v3 01/24] xen: Extend DOMCTL createdomain to support arch configuration

[Ian Campbell <ian.campbell@citrix.com>]

On Mon, 2015-02-23 at 21:48 +0000, Julien Grall wrote:
> Hi Ian,
> 
> On 23/02/2015 16:00, Ian Campbell wrote:
> > On Mon, 2015-02-23 at 15:48 +0000, Andrew Cooper wrote:
> >> GIC version and SPIs should absolutely be part of the migration stream.
> >> They are domain architectural state.
> >
> > Of course, the question is where.
> >
> > They could be part of the Xen hvmsave blob for the GIC (i.e. along with
> > the other GIC architectural state such as which interrupts are currently
> > active,pending,masked etc).
> >
> > Or they could be part of a new migration v2 record for such things.
> 
> With the extension of the DOMCTL createdomain, this would be the best 
> solution. The implementation would be cleaner.

and this sounds like it fits in with the approach Andrew wants to take
for x86 too.

> > Or they could be part of the hvm params migration record.
> 
> And how do you restore? As we may have some default value (such as 
> choosing the default GIC version), how do you know that all the 
> parameters is correctly given?

IIRC the migration v2 has a list of hvm params to transport in the save
stream (either in a dedicated record or one per param, I don't recall),
i.e. it reads them back on the source and writes them on the target.

The read would presumably have to reflect the actual selection made for
that domain if there was defaulting going on and the write would have to
reject things it couldn't deal with (like GICv2 on v3 only hardware).

Ian.