Re: [Xen-devel] [PATCH 1/1] xc_domain_restore: Allow QEMU to increase memory

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Wed, 2015-04-15 at 12:27 +0100, Stefano Stabellini wrote:
> On Wed, 15 Apr 2015, Hongyang Yang wrote:
> > On 04/15/2015 06:09 PM, Ian Campbell wrote:
> > > On Wed, 2015-04-15 at 10:46 +0100, Stefano Stabellini wrote:
> > > > On Tue, 14 Apr 2015, Don Slutz wrote:
> > > > > On 04/14/15 04:53, Wei Liu wrote:
> > > > > > Is there a way to know how much more memory each option rom needs? 
> > > > > > If
> > > > > > so, you can correctly account for the extra memory you need. This
> > > > > > would
> > > > > > be an ideal fix to this problem.
> > > > > 
> > > > > I do not know of a way to get this info.  It can change based on the
> > > > > QEMU version.
> > > > 
> > > > Indeed it would be fragile to rely on a fixed size for each option rom,
> > > > given that they come out of the QEMU tree and can change at any time.
> > > 
> > > Only having dipped into this thread so far it seems to me we need some
> > > way for qemu to communicate the result of its manipulations of maxmem
> > > into the migration stream explicitly to be picked up by the other end.
> > 
> > Totally agreed.
> 
> Xen knows exactly the maxmem setting for the domain, I don't think we
> need one more notification from QEMU?
> Libxl/Xen could just write the maxmem value to the migration stream.

If that is all which is needed and not the delta between the notional
maxmem which the guest was configured with and what we actually gave it
due to things such as option ROMs, then sure.

Ian.


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