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Subject[PATCH v2] device-dax: use fallback nid when numa node is invalid
Date
Previously, numa_off was set unconditionally in dummy_numa_init()
even with a fake numa node. Then ACPI sets node id as NUMA_NO_NODE(-1)
after acpi_map_pxm_to_node() because it regards numa_off as turning
off the numa node. Hence dev_dax->target_node is NUMA_NO_NODE on
arm64 with fake numa case.

Without this patch, pmem can't be probed as RAM devices on arm64 if
SRAT table isn't present:
$ndctl create-namespace -fe namespace0.0 --mode=devdax --map=dev -s 1g -a 64K
kmem dax0.0: rejecting DAX region [mem 0x240400000-0x2bfffffff] with invalid node: -1
kmem: probe of dax0.0 failed with error -22

This fixes it by using fallback memory_add_physaddr_to_nid() as nid.

Suggested-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Jia He <justin.he@arm.com>
---
v2: - rebase it based on David's "memory group" patch.
- drop the changes in dev_dax_kmem_remove() since nid had been
removed in remove_memory().
drivers/dax/kmem.c | 31 +++++++++++++++++--------------
1 file changed, 17 insertions(+), 14 deletions(-)

diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
index a37622060fff..e4836eb7539e 100644
--- a/drivers/dax/kmem.c
+++ b/drivers/dax/kmem.c
@@ -47,20 +47,7 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
unsigned long total_len = 0;
struct dax_kmem_data *data;
int i, rc, mapped = 0;
- int numa_node;
-
- /*
- * Ensure good NUMA information for the persistent memory.
- * Without this check, there is a risk that slow memory
- * could be mixed in a node with faster memory, causing
- * unavoidable performance issues.
- */
- numa_node = dev_dax->target_node;
- if (numa_node < 0) {
- dev_warn(dev, "rejecting DAX region with invalid node: %d\n",
- numa_node);
- return -EINVAL;
- }
+ int numa_node = dev_dax->target_node;

for (i = 0; i < dev_dax->nr_range; i++) {
struct range range;
@@ -71,6 +58,22 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
i, range.start, range.end);
continue;
}
+
+ /*
+ * Ensure good NUMA information for the persistent memory.
+ * Without this check, there is a risk but not fatal that slow
+ * memory could be mixed in a node with faster memory, causing
+ * unavoidable performance issues. Warn this and use fallback
+ * node id.
+ */
+ if (numa_node < 0) {
+ int new_node = memory_add_physaddr_to_nid(range.start);
+
+ dev_info(dev, "changing nid from %d to %d for DAX region [%#llx-%#llx]\n",
+ numa_node, new_node, range.start, range.end);
+ numa_node = new_node;
+ }
+
total_len += range_len(&range);
}

--
2.17.1
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