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SubjectRe: [patch] x86: set hotpluggable nodes in nodes_possible_map
On Wed, 20 Jan 2010, Yinghai Lu wrote:

> > nodes_possible_map does not currently include nodes that have SRAT
> > entries that are all ACPI_SRAT_MEM_HOT_PLUGGABLE since the bit is cleared
> > in nodes_parsed if it does not have an online address range.
> >
> > Unequivocally setting the bit in nodes_parsed is insufficient since
> > existing code, such as acpi_get_nodes(), assumes all nodes in the map
> > have online address ranges. In fact, all code using nodes_parsed assumes
> > such nodes represent an address range of online memory.
> >
> > nodes_possible_map is created by unioning nodes_parsed and
> > cpu_nodes_parsed; the former represents nodes with online memory and the
> > latter represents memoryless nodes. We now set the bit for hotpluggable
> > nodes in cpu_nodes_parsed so that it also gets set in nodes_possible_map.
> >
> > Signed-off-by: David Rientjes <rientjes@google.com>
> > ---
> > arch/x86/mm/srat_64.c | 4 +++-
> > 1 files changed, 3 insertions(+), 1 deletions(-)
> >
> > diff --git a/arch/x86/mm/srat_64.c b/arch/x86/mm/srat_64.c
> > --- a/arch/x86/mm/srat_64.c
> > +++ b/arch/x86/mm/srat_64.c
> > @@ -229,9 +229,11 @@ update_nodes_add(int node, unsigned long start, unsigned long end)
> > printk(KERN_ERR "SRAT: Hotplug zone not continuous. Partly ignored\n");
> > }
> >
> > - if (changed)
> > + if (changed) {
> > + node_set(node, cpu_nodes_parsed);
> > printk(KERN_INFO "SRAT: hot plug zone found %Lx - %Lx\n",
> > nd->start, nd->end);
> > + }
> > }
> >
> > /* Callback for parsing of the Proximity Domain <-> Memory Area mappings */
>
> if (ma->flags & ACPI_SRAT_MEM_HOT_PLUGGABLE) {
> update_nodes_add(node, start, end);
> /* restore nodes[node] */
> *nd = oldnode;
> if ((nd->start | nd->end) == 0)
> node_clear(node, nodes_parsed);
> }
>
> removing clearing with nodes_parsed is not working?
>

As previously discussed in this thread, the semantics of nodes_parsed is
to define nodes that have online address ranges; all code written to use
nodes_parsed operates on those address ranges. Requiring it to also
support memoryless (or hotpluggable) nodes would require a change in
semantics in other areas such as acpi_get_nodes() and would be contrary to
the effort in dc098551 to fix this inconsistency.

I believe Haicheng will be posting an incremental patch that changes the
name of cpu_nodes_parsed to something such as acpi_nodes_parsed to
indicate it does not necessarily represent memory but rather another ACPI
definition: either a node including only cpus or hotpluggable ranges.


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