Re: [libvirt] [PATCH] qemu: Only use memory-backend-file with NUMA if needed

On Fri, Sep 23, 2016 at 03:20:56PM +0200, Martin Kletzander wrote: > If this reminds you of a commit message from around a year ago, it's > 41c2aa729f0af084ede95ee9a06219a2dd5fb5df and yes, we're dealing with > "the same thing" again. Or f309db1f4d51009bad0d32e12efc75530b66836b and > it's similar. > > There is a logic in place that if there is no real need for > memory-backend-file, qemuBuildMemoryBackendStr() returns 0. However > that wasn't the case with hugepage backing. The reason for that was > that we abused the 'pagesize' variable for storing that information, but > we should rather have a separate one that specifies whether we really > need the new object for hugepage backing. And that variable should be > set only if this particular NUMA cell needs special treatment WRT > hugepages. > > Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1372153 > > Signed-off-by: Martin Kletzander <mkletzan(a)redhat.com&gt; Hi Martin, I tested your patch and it works but it seems to make the snapshot/migration information incompatible with the current master code. e.g. after applying the patch I can't load a snapshot that was created before applying the patch (obviously only for a guest configuration that is affected by the patch). The error I get is this: $ virsh snapshot-revert tmp --snapshotname 1475026515 error: operation failed: Unknown ramblock "/objects/ram-node0", cannot accept migration error while loading state for instance 0x0 of device 'ram' Error -22 while loading VM state Presumably this is caused by the same change that fixes some other migrations, but is this case a problem?

Cheers, Sam. > --- > > Notes: > This fixes migration from older libvirts. By "older", I mean > pre-(circa-)1.2.7, also in some cases pre-1.2.11, in some other cases > pre-v1.2.20. It's pretty messy. It could be back-ported as far as it's > easy to do. >