On 24 June 2016 at 07:36, Paolo Bonzini <pbonz...@redhat.com> 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
