Re: [Qemu-devel] [PULL 5/8] target-sparc: Use global registers for the register window

[Peter Maydell]

On 24 June 2016 at 07:36, Paolo Bonzini <address@hidden> wrote:
> Mark, perhaps you can try to use migration to reduce the amount of
> logging?  (Start QEMU with -snapshot, try to stop the vm before it
> fails.  If you succeed, do a "migrate exec:cat>foo.sav" followed by
> "commit"; if you fail, try again).

Why drag migration into it? I usually use 'savevm' and then
the -loadvm command line argument for this. (You need a
qcow2 disk image.)

> It would be nice to have a mechanism to stop the VM after executing N
> basic blocks.  Binary search on this value then can help with coming up
> with a more easily debuggable snapshot, possibly to a point where the
> difference between pre-patch and post-patch becomes deterministic.

You can use the monitor and an expect script to say "take a
snapshot 0.7 seconds into boot", which I've found to be
a good enough approximation:

https://translatedcode.wordpress.com/2015/07/06/tricks-for-debugging-qemu-savevm-snapshots/

thanks
-- PMM