Re: [Qemu-devel] [PATCH v2 6/6] hw/arm/virt: Set minimum_page_bits to 12

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Peter Maydell (peter.maydell@linaro.org) wrote:
> On 22 June 2016 at 12:54, Dr. David Alan Gilbert <dgilbert@redhat.com> wrote:
> > * Peter Maydell (peter.maydell@linaro.org) wrote:
> >> On 22 June 2016 at 12:35, Dr. David Alan Gilbert <dgilbert@redhat.com> wrote:
> >> > Yes, my hope is that any versioned machine type should migrate to
> >> > a newer qemu with the same machine type set.
> >> >
> >> > There are really two separate things that we state with the machine
> >> > versioning:
> >> >   a) that the guest view is the same
> >> >   b) that the migration format is the same
> >>
> >> Well, this is true for PC.
> >
> > PC, ppc/spapr, and I think s390.
> >
> >> But my impression when we started
> >> applying versioned machine types to ARM virt was that it was
> >> signing up to (a) but not (yet) (b)...
> >
> > So that would make ARM special; the problem is we have no way
> > to communicate to the user that it's special.
> 
> Is anybody testing that migration between versions for
> virt works?

I don't know (Perhaps Drew knows), but I'd love to add
a make check test for the x86 equivalent, but there's two
things I'm stuck on;
   1) What to run in the guest to check it survives
   2) How to know we have an old qemu binary to check.

  I was thinking for (2) I could use an environment variable
and if it's not set then skip the test.
  For (1) perhaps a trivial little image (like I use for postcopy)
that wouldn't check much except that the CPU/serial is still happy,
but at least migration completed OK.

  You could use virt-test/avocado to run a test with a full guest;
it has options to specify source and destination qemu's separately.

Dave

> 
> thanks
> -- PMM
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK