Re: [Qemu-devel] [PATCH v2] hw/acpi: Select an node with memory for mapping memory hole to

[Eduardo Habkost <ehabkost@redhat.com>]

On Wed, Aug 16, 2017 at 11:18:07AM +0200, Igor Mammedov wrote:
> On Wed, 16 Aug 2017 09:26:51 +0800
> Dou Liyang <douly.fnst@cn.fujitsu.com> wrote:
> 
> > Currently, Using the fisrt node without memory on the machine makes
> > QEMU unhappy. With this example command line:
> >   ... \
> >   -m 1024M,slots=4,maxmem=32G \
> >   -numa node,nodeid=0 \
> >   -numa node,mem=1024M,nodeid=1 \
> >   -numa node,nodeid=2 \
> >   -numa node,nodeid=3 \
> > Guest reports "No NUMA configuration found" and the NUMA topology is
> > wrong.
> > 
> > This is because when QEMU builds ACPI SRAT, it regards node0 as the
> > default node to deal with the memory hole(640K-1M). this means the
> > node0 must have some memory(>1M), but, actually it can have no
> > memory.
> > 
> > Fix this problem by replace the node0 with the first node which has
> > memory on it. Add a new function for each node. Also do some cleanup.
> It seems harmless but one never knows for sure,
> could you test it with different guests including old windows (up to XP)/
> linux (2.6 stable kernel) versions?

This patch is supposed to affect only the cases where there's no
RAM configured on node 0.  I won't be surprised if some guest
OSes don't like it, but in this case the solution is to not
configure the VM that way.

That means I don't think we really need to test ancient OSes if
we ensure there are no ACPI table changes on the existing
known-to-work configurations.

-- 
Eduardo