[libvirt] [PATCH] qemu: Create memory-backend-{ram, file} iff needed

[Daniel P. Berrange]

On Thu, Dec 18, 2014 at 12:46:32PM +0100, Michal Privoznik wrote:
> 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 at redhat.com>
> ---
>  src/qemu/qemu_command.c                                  | 16 +++++++++-------
>  .../qemuxml2argvdata/qemuxml2argv-hugepages-pages3.args  |  3 +--
>  .../qemuxml2argv-numatune-memnode-no-memory.args         |  3 +--
>  3 files changed, 11 insertions(+), 11 deletions(-)

ACK, that looks reasonable to me.

Regards,
Daniel
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