diff --git a/mm/cma.c b/mm/cma.c
index c960459eda7e..94b3460cd608 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -235,18 +235,13 @@ int __init cma_declare_contiguous(phys_addr_t base,
 	phys_addr_t highmem_start;
 	int ret = 0;
 
-#ifdef CONFIG_X86
 	/*
-	 * high_memory isn't direct mapped memory so retrieving its physical
-	 * address isn't appropriate.  But it would be useful to check the
-	 * physical address of the highmem boundary so it's justifiable to get
-	 * the physical address from it.  On x86 there is a validation check for
-	 * this case, so the following workaround is needed to avoid it.
+	 * We can't use __pa(high_memory) directly, since high_memory
+	 * isn't a valid direct map VA, and DEBUG_VIRTUAL will (validly)
+	 * complain. Find the boundary by adding one to the last valid
+	 * address.
 	 */
-	highmem_start = __pa_nodebug(high_memory);
-#else
-	highmem_start = __pa(high_memory);
-#endif
+	highmem_start = __pa(high_memory - 1) + 1;
 	pr_debug("%s(size %pa, base %pa, limit %pa alignment %pa)\n",
 		__func__, &size, &base, &limit, &alignment);