Re: [Qemu-devel] [RFC PATCH] numa: add auto_enable_numa to fix broken check in spapr

[David Gibson <david@gibson.dropbear.id.au>]

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On Mon, Aug 05, 2019 at 08:56:40AM +0800, Tao Xu wrote:
> On 8/2/2019 2:55 PM, David Gibson wrote:
> > On Thu, Aug 01, 2019 at 03:52:58PM +0800, Tao Xu wrote:
> > > Introduce MachineClass::auto_enable_numa for one implicit NUMA node,
> > > and enable it to fix broken check in spapr_validate_node_memory(), when
> > > spapr_populate_memory() creates a implicit node and info then use
> > > nb_numa_nodes which is 0.
> > > 
> > > Suggested-by: Igor Mammedov <imammedo@redhat.com>
> > > Suggested-by: Eduardo Habkost <ehabkost@redhat.com>
> > > Signed-off-by: Tao Xu <tao3.xu@intel.com>
> > 
> > The change here looks fine so,
> > 
> > Acked-by: David Gibson <david@gibson.dropbear.id.au>
> > 
> > However, I'm not following what check in spapr is broken and why.
> > 
> Sorry, may be I should update the commit message.
> 
> Because in spapr_populate_memory(), if numa node is 0
> 
>     if (!nb_nodes) {
>         nb_nodes = 1;
>         ramnode.node_mem = machine->ram_size;
>         nodes = &ramnode;
>     }
> 
> it use a local 'nb_nodes' as 1 and update global nodes info, but
> inpapr_validate_node_memory(), use the global nb_numa_nodes
> 
>     for (i = 0; i < nb_numa_nodes; i++) {
>     	if (numa_info[i].node_mem % SPAPR_MEMORY_BLOCK_SIZE) {
> 
> so the global is 0 and skip the node_mem check.

Well, not really.  That loop is that each node has memory size a
multiple of 256MiB.  But we've already checked that the whole memory
size is a multiple of 256MiB, so in the case of one NUMA node, the
per-node check doesn't actually do anything extra.

And in the "non-NUMA" case, nb_numa_nodes == 0, then I don't believe
numa_info[] is populated anyway, so we couldn't do the check like
this.


> > > ---
> > > 
> > > This patch has a dependency on
> > > https://patchwork.kernel.org/cover/11063235/
> > > ---
> > >   hw/core/numa.c      | 9 +++++++--
> > >   hw/ppc/spapr.c      | 9 +--------
> > >   include/hw/boards.h | 1 +
> > >   3 files changed, 9 insertions(+), 10 deletions(-)
> > > 
> > > diff --git a/hw/core/numa.c b/hw/core/numa.c
> > > index 75db35ac19..756d243d3f 100644
> > > --- a/hw/core/numa.c
> > > +++ b/hw/core/numa.c
> > > @@ -580,9 +580,14 @@ void numa_complete_configuration(MachineState *ms)
> > >        *   guest tries to use it with that drivers.
> > >        *
> > >        * Enable NUMA implicitly by adding a new NUMA node automatically.
> > > +     *
> > > +     * Or if MachineClass::auto_enable_numa is true and no NUMA nodes,
> > > +     * assume there is just one node with whole RAM.
> > >        */
> > > -    if (ms->ram_slots > 0 && ms->numa_state->num_nodes == 0 &&
> > > -        mc->auto_enable_numa_with_memhp) {
> > > +    if (ms->numa_state->num_nodes == 0 &&
> > > +        ((ms->ram_slots > 0 &&
> > > +        mc->auto_enable_numa_with_memhp) ||
> > > +        mc->auto_enable_numa)) {
> > >               NumaNodeOptions node = { };
> > >               parse_numa_node(ms, &node, &error_abort);
> > >       }
> > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > > index f607ca567b..e50343f326 100644
> > > --- a/hw/ppc/spapr.c
> > > +++ b/hw/ppc/spapr.c
> > > @@ -400,14 +400,6 @@ static int spapr_populate_memory(SpaprMachineState *spapr, void *fdt)
> > >       hwaddr mem_start, node_size;
> > >       int i, nb_nodes = machine->numa_state->num_nodes;
> > >       NodeInfo *nodes = machine->numa_state->nodes;
> > > -    NodeInfo ramnode;
> > > -
> > > -    /* No NUMA nodes, assume there is just one node with whole RAM */
> > > -    if (!nb_nodes) {
> > > -        nb_nodes = 1;
> > > -        ramnode.node_mem = machine->ram_size;
> > > -        nodes = &ramnode;
> > > -    }
> > >       for (i = 0, mem_start = 0; i < nb_nodes; ++i) {
> > >           if (!nodes[i].node_mem) {
> > > @@ -4369,6 +4361,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
> > >        */
> > >       mc->numa_mem_align_shift = 28;
> > >       mc->numa_mem_supported = true;
> > > +    mc->auto_enable_numa = true;
> > >       smc->default_caps.caps[SPAPR_CAP_HTM] = SPAPR_CAP_OFF;
> > >       smc->default_caps.caps[SPAPR_CAP_VSX] = SPAPR_CAP_ON;
> > > diff --git a/include/hw/boards.h b/include/hw/boards.h
> > > index 2eb9a0b4e0..4a350b87d2 100644
> > > --- a/include/hw/boards.h
> > > +++ b/include/hw/boards.h
> > > @@ -220,6 +220,7 @@ struct MachineClass {
> > >       bool smbus_no_migration_support;
> > >       bool nvdimm_supported;
> > >       bool numa_mem_supported;
> > > +    bool auto_enable_numa;
> > >       HotplugHandler *(*get_hotplug_handler)(MachineState *machine,
> > >                                              DeviceState *dev);
> > 
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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