Change done by commit f309db1f4d wrongly
assumes that qemu can start with a combination of NUMA nodes specified
with the "memdev" option and the appropriate backends, and the legacy
way by specifying only "mem" as a size argument. QEMU rejects such
commandline though:
$ /usr/bin/qemu-system-x86_64 -S -M pc -m 1024 -smp 2 \
-numa node,nodeid=0,cpus=0,mem=256 \
-object memory-backend-ram,id=ram-node1,size=12345 \
-numa node,nodeid=1,cpus=1,memdev=ram-node1
qemu-system-x86_64: -numa node,nodeid=1,cpus=1,memdev=ram-node1: qemu: memdev option must be specified for either all or no nodes
To fix this issue we need to check if any of the nodes requires the new
definition with the backend and if so, then all other nodes have to use
it too.
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1182467
QEMU's command line visitor as well as the JSON interface take bytes by
default for memory object sizes. Convert mebibytes to bytes so that we
can later refactor the existing code for hotplug purposes.
Libvirt BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1175397
QEMU BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1170093
In qemu there are two interesting arguments:
1) -numa to create a guest NUMA node
2) -object memory-backend-{ram,file} to tell qemu which memory
region on which host's NUMA node it should allocate the guest
memory from.
Combining these two together we can instruct qemu to create a
guest NUMA node that is tied to a host NUMA node. And it works
just fine. However, depending on machine type used, there might
be some issued during migration when OVMF is enabled (see QEMU
BZ). While this truly is a QEMU bug, we can help avoiding it. The
problem lies within the memory backend objects somewhere. Having
said that, fix on our side consists on putting those objects on
the command line if and only if needed. For instance, while
previously we would construct this (in all ways correct) command
line:
-object memory-backend-ram,size=256M,id=ram-node0 \
-numa node,nodeid=0,cpus=0,memdev=ram-node0
now we create just:
-numa node,nodeid=0,cpus=0,mem=256
because the backend object is obviously not tied to any specific
host NUMA node.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
