On Wed, Mar 04, 2015 at 01:30:35PM +0100, Michael S. Tsirkin wrote:
> On Tue, Feb 24, 2015 at 03:57:23PM -0300, Eduardo Habkost wrote:
> > Instead of silently assigning CPU to node 0 when it is omitted from the
> > command-line, check if all CPUs up to max_cpus are present in the NUMA
> > configuration.
>
> Could you please describe the problematic configuration
> in more detail in commit log?
> Also, how does this interact with cpu hotplug?
I will try to reword the message to make it clearer. Suggestions are
welcome.
Basically, the problem is:
* Currently all possible CPUs (including hotplug ones) need to be
present in the SRAT when QEMU is started[1]. QEMU already does that.
* When a CPU is ommitted from the command-line, QEMU is silently
assigning it to node 0. This is not a very useful default and
just confuse users.
> >
> > I am making this a warning and not a fatal error, to allow management
> > software to be updated if necessary.
> >
> > Signed-off-by: Eduardo Habkost <ehabk...@redhat.com>
> > ---
> > v1 -> v2: (no changes)
> >
> > v2 -> v3:
> > * Use enumerate_cpus() and error_report() for error message
> > * Simplify logic using bitmap_full()
> >
> > v3 -> v4:
> > * Clarify error message, mention that all CPUs up to
> > maxcpus need to be described in NUMA config
> > ---
> > numa.c | 10 ++++++++++
> > 1 file changed, 10 insertions(+)
> >
> > diff --git a/numa.c b/numa.c
> > index 9a3fc15..d8021b9 100644
> > --- a/numa.c
> > +++ b/numa.c
> > @@ -201,6 +201,16 @@ static void validate_numa_cpus(void)
> > bitmap_or(seen_cpus, seen_cpus,
> > numa_info[i].node_cpu, MAX_CPUMASK_BITS);
> > }
> > +
> > + if (!bitmap_full(seen_cpus, max_cpus)) {
> > + char *msg;
> > + bitmap_complement(seen_cpus, seen_cpus, max_cpus);
> > + msg = enumerate_cpus(seen_cpus, max_cpus);
> > + error_report("warning: CPU(s) not present in any NUMA nodes: %s",
> > msg);
> > + error_report("warning: All CPU(s) up to maxcpus should be
> > described "
> > + "in NUMA config");
>
> What happens with e.g. windows guests when this warning is emitted?
> do they blue-screen?
As described on the commit log above, the CPU is silently assigned to
node 0 when it is omitted from the command-line. In other words, this
won't make guests confused, but can make users confused.
All possible VCPUs (including the hotplug ones, i.e. up to max_cpus) are
expected to be present in the SRAT, and they are already present. The
only problem is that instead of complaining about missing CPUs, QEMU is
assigning node 0 to them.
--
Eduardo
