On Sat, Apr 08, 2017 at 06:09:16PM +0800, Paolo Bonzini wrote: > On 07/04/2017 19:33, Stefan Hajnoczi wrote: > > The migration thread is holding the QEMU global mutex, the AioContext, > > and the qcow2 s->lock while the L2 table is read from disk. > > > > The QEMU global mutex is needed for block layer operations that touch > > the global drives list. bdrv_is_allocated() can be called without the > > global mutex. > > Hi Stefan, > > only virtio-blk and virtio-scsi take the AioContext lock (because they > support dataplane). For block migration to work with devices such as > IDE, it needs to take the iothread lock too. I think there's a comment > about this in migration/block.c.
Good point. :( Stefan
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