4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: John Garry john.garry@huawei.com
commit 89c38422e072bb453e3045b8f1b962a344c3edea upstream.
Currently the NUMA distance map parsing does not validate the distance table for the distance-matrix rules 1-2 in [1].
However the arch NUMA code may enforce some of these rules, but not all. Such is the case for the arm64 port, which does not enforce the rule that the distance between separates nodes cannot equal LOCAL_DISTANCE.
The patch adds the following rules validation: - distance of node to self equals LOCAL_DISTANCE - distance of separate nodes > LOCAL_DISTANCE
This change avoids a yet-unresolved crash reported in [2].
A note on dealing with symmetrical distances between nodes:
Validating symmetrical distances between nodes is difficult. If it were mandated in the bindings that every distance must be recorded in the table, then it would be easy. However, it isn't.
In addition to this, it is also possible to record [b, a] distance only (and not [a, b]). So, when processing the table for [b, a], we cannot assert that current distance of [a, b] != [b, a] as invalid, as [a, b] distance may not be present in the table and current distance would be default at REMOTE_DISTANCE.
As such, we maintain the policy that we overwrite distance [a, b] = [b, a] for b > a. This policy is different to kernel ACPI SLIT validation, which allows non-symmetrical distances (ACPI spec SLIT rules allow it). However, the distance debug message is dropped as it may be misleading (for a distance which is later overwritten).
Some final notes on semantics:
- It is implied that it is the responsibility of the arch NUMA code to reset the NUMA distance map for an error in distance map parsing.
- It is the responsibility of the FW NUMA topology parsing (whether OF or ACPI) to enforce NUMA distance rules, and not arch NUMA code.
[1] Documents/devicetree/bindings/numa.txt [2] https://www.spinics.net/lists/arm-kernel/msg683304.html
Cc: stable@vger.kernel.org # 4.7 Signed-off-by: John Garry john.garry@huawei.com Acked-by: Will Deacon will.deacon@arm.com Signed-off-by: Rob Herring robh@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/of/of_numa.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
--- a/drivers/of/of_numa.c +++ b/drivers/of/of_numa.c @@ -126,9 +126,14 @@ static int __init of_numa_parse_distance distance = of_read_number(matrix, 1); matrix++;
+ if ((nodea == nodeb && distance != LOCAL_DISTANCE) || + (nodea != nodeb && distance <= LOCAL_DISTANCE)) { + pr_err("Invalid distance[node%d -> node%d] = %d\n", + nodea, nodeb, distance); + return -EINVAL; + } + numa_set_distance(nodea, nodeb, distance); - pr_debug("distance[node%d -> node%d] = %d\n", - nodea, nodeb, distance);
/* Set default distance of node B->A same as A->B */ if (nodeb > nodea)