On Fri 30-08-19 14:35:26, Yunsheng Lin wrote:

On 2019/8/30 13:55, Michal Hocko wrote:

quoted

On Fri 30-08-19 10:26:31, Yunsheng Lin wrote:

quoted

Some buggy bios may not set the device' numa id, and dev_to_node
will return -1, which may cause global-out-of-bounds error
detected by KASAN.

Why should we workaround a buggy bios like that? Is it so widespread and
no BIOS update available? Also, why is this arm64 specific?

For our case, there is BIOS update available. I just thought it might
be better to protect from this case when BIOS has not implemented the
device' numa id setting feature or the feature from BIOS has some bug.

It is not arm64 specific, right now I only have arm64 board. If it is
ok to protect this from the buggy BIOS, maybe all other arch can be
changed too.

If we are to really care then this should be consistent among
architectures IMHO. But I am not really sure this is really worth it.
The code is quite old and I do not really remember any reports. 

quoted

quoted

This patch changes cpumask_of_node to return cpu_none_mask if the
node is not valid, and sync the cpumask_of_node between the
cpumask_of_node function in numa.h and numa.c.

Why?

When CONFIG_DEBUG_PER_CPU_MAPS is defined, the cpumask_of_node() in
numa.c is used, if not, the cpumask_of_node() in numa.h is used.

I am not sure why there is difference between them, and it is there
when since the below commit:
1a2db300348b ("arm64, numa: Add NUMA support for arm64 platforms.")

I synced them to keep them consistent whether CONFIG_DEBUG_PER_CPU_MAPS
is defined.

Such a change should be made in a separate patch with a full
clarification/justification. From the above it is still not clear why
this is needed though.

quoted

quoted

Signed-off-by: Yunsheng Lin <redacted>
---
 arch/arm64/include/asm/numa.h | 6 ++++++
 arch/arm64/mm/numa.c          | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/numa.h b/arch/arm64/include/asm/numa.h
index 626ad01..da891ed 100644
--- a/arch/arm64/include/asm/numa.h
+++ b/arch/arm64/include/asm/numa.h

@@ -25,6 +25,12 @@ const struct cpumask *cpumask_of_node(int node);
 /* Returns a pointer to the cpumask of CPUs on Node 'node'. */
 static inline const struct cpumask *cpumask_of_node(int node)
 {
+	if (node >= nr_node_ids || node < 0)
+		return cpu_none_mask;
+
+	if (!node_to_cpumask_map[node])
+		return cpu_online_mask;
+
 	return node_to_cpumask_map[node];
 }
 #endif

diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
index 4f241cc..3846313 100644
--- a/arch/arm64/mm/numa.c
+++ b/arch/arm64/mm/numa.c

@@ -46,7 +46,7 @@ EXPORT_SYMBOL(node_to_cpumask_map);
  */
 const struct cpumask *cpumask_of_node(int node)
 {
-	if (WARN_ON(node >= nr_node_ids))
+	if (WARN_ON(node >= nr_node_ids || node < 0))
 		return cpu_none_mask;
 
 	if (WARN_ON(node_to_cpumask_map[node] == NULL))

-- 
2.8.1

-- 
Michal Hocko
SUSE Labs

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