On Tue, Jan 17, 2023 at 12:22:41PM +0100, David Hildenbrand wrote: > While playing with migration of virtio-mem with an ordinary file backing, > I realized that migration and prealloc doesn't currently work as expected > for virtio-mem. Further, Jing Qi reported that setup issues (insufficient > huge pages on the destination) result in QEMU getting killed with SIGBUS > instead of failing gracefully. > > In contrast to ordinary memory backend preallocation, virtio-mem > preallocates memory before plugging blocks to the guest. Consequently, > when migrating we are not actually preallocating on the destination but > "only" migrate pages. Fix that be migrating the bitmap early, before any > RAM content, and use that information to preallocate memory early, before > migrating any RAM. > > Postcopy needs some extra care, and I realized that prealloc+postcopy is > shaky in general. Let's at least try to mimic what ordinary > prealloc+postcopy does: temporarily allocate the memory, discard it, and > cross fingers that we'll still have sufficient memory when postcopy > actually tries placing pages. > > Cc: Dr. David Alan Gilbert <dgilb...@redhat.com> > Cc: Juan Quintela <quint...@redhat.com> > Cc: Peter Xu <pet...@redhat.com> > Cc: Michael S. Tsirkin <m...@redhat.com> > Cc: Michal Privoznik <mpriv...@redhat.com>
For patch 1-5: Reviewed-by: Peter Xu <pet...@redhat.com> -- Peter Xu
