[PATCH 3/3] xen/common: Add NUMA node id bounds check to page_alloc.c/node_to_scrub

[Shawn Anastasio <sanastasio@xxxxxxxxxxxxxxxxxxxxx>]

When building for Power with CONFIG_DEBUG unset, a compiler error gets
raised inside page_alloc.c's node_to_scrub function, likely due to the
increased optimization level:

common/page_alloc.c: In function 'node_to_scrub.part.0':
common/page_alloc.c:1217:29: error: array subscript 1 is above array
            bounds of 'long unsigned int[1]' [-Werror=array-bounds]
 1217 |         if ( node_need_scrub[node] )

It appears that this is a false positive, given that in practice
cycle_node should never return a node ID >= MAX_NUMNODES as long as the
architecture's node_online_map is properly defined and initialized, so
this additional bounds check is only to satisfy GCC.

Signed-off-by: Shawn Anastasio <sanastasio@xxxxxxxxxxxxxxxxxxxxx>
---
 xen/common/page_alloc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 35d9a26fa6..6df2a223e1 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -1211,6 +1211,9 @@ static unsigned int node_to_scrub(bool get_node)
         } while ( !cpumask_empty(&node_to_cpumask(node)) &&
                   (node != local_node) );

+        if ( node >= MAX_NUMNODES )
+            break;
+
         if ( node == local_node )
             break;

--
2.30.2