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-rw-r--r--drivers/misc/cxl/fault.c14
1 files changed, 12 insertions, 2 deletions
diff --git a/drivers/misc/cxl/fault.c b/drivers/misc/cxl/fault.c
index ab507e4ed69b..f17f72ea0545 100644
--- a/drivers/misc/cxl/fault.c
+++ b/drivers/misc/cxl/fault.c
@@ -141,9 +141,19 @@ int cxl_handle_mm_fault(struct mm_struct *mm, u64 dsisr, u64 dar)
/*
* Add the fault handling cpu to task mm cpumask so that we
* can do a safe lockless page table walk when inserting the
- * hash page table entry.
+ * hash page table entry. This function get called with a
+ * valid mm for user space addresses. Hence using the if (mm)
+ * check is sufficient here.
*/
- cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
+ if (mm && !cpumask_test_cpu(smp_processor_id(), mm_cpumask(mm))) {
+ cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
+ /*
+ * We need to make sure we walk the table only after
+ * we update the cpumask. The other side of the barrier
+ * is explained in serialize_against_pte_lookup()
+ */
+ smp_mb();
+ }
if ((result = copro_handle_mm_fault(mm, dar, dsisr, &flt))) {
pr_devel("copro_handle_mm_fault failed: %#x\n", result);
return result;