diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 08013524fba18ebe2afc44bf798c5ad77839fa0b..4fe956a63b25b54fe479aadfeb51dfdf66ef74d2 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -519,8 +519,13 @@ static u64 sanitize_phys(u64 address)
 	 * for a "decoy" virtual address (bit 63 clear) passed to
 	 * set_memory_X(). __pa() on a "decoy" address results in a
 	 * physical address with bit 63 set.
+	 *
+	 * Decoy addresses are not present for 32-bit builds, see
+	 * set_mce_nospec().
 	 */
-	return address & __PHYSICAL_MASK;
+	if (IS_ENABLED(CONFIG_X86_64))
+		return address & __PHYSICAL_MASK;
+	return address;
 }
 
 /*
@@ -546,7 +551,11 @@ int reserve_memtype(u64 start, u64 end, enum page_cache_mode req_type,
 
 	start = sanitize_phys(start);
 	end = sanitize_phys(end);
-	BUG_ON(start >= end); /* end is exclusive */
+	if (start >= end) {
+		WARN(1, "%s failed: [mem %#010Lx-%#010Lx], req %s\n", __func__,
+				start, end - 1, cattr_name(req_type));
+		return -EINVAL;
+	}
 
 	if (!pat_enabled()) {
 		/* This is identical to page table setting without PAT */