selftests/mm: skip test for non-LPA2 and non-LVA systems

Post my improvement of the test in e4a4ba4 ("selftests/mm:
va_high_addr_switch: dynamically initialize testcases to enable LPA2
testing"):

The test begins to fail on 4k and 16k pages, on non-LPA2 systems.  To
reduce noise in the CI systems, let us skip the test when higher address
space is not implemented.

Link: https://lkml.kernel.org/r/20240718052504.356517-1-dev.jain@arm.com
Fixes: e4a4ba4 ("selftests/mm: va_high_addr_switch: dynamically initialize testcases to enable LPA2 testing")
Signed-off-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: Dev Jain

tools/testing/selftests/mm/va_high_addr_switch.c

@@ -293,14 +293,28 @@ static int run_test(struct testcase *test, int count)
 	return ret;
 }
 
+#ifdef __aarch64__
+/* Check if userspace VA > 48 bits */
+static int high_address_present(void)
+{
+	void *ptr = mmap((void *)(1UL << 50), 1, PROT_READ | PROT_WRITE,
+			 MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
+	if (ptr == MAP_FAILED)
+		return 0;
+
+	munmap(ptr, 1);
+	return 1;
+}
+#endif
+
 static int supported_arch(void)
 {
 #if defined(__powerpc64__)
 	return 1;
 #elif defined(__x86_64__)
 	return 1;
 #elif defined(__aarch64__)
-	return 1;
+	return high_address_present();
 #else
 	return 0;
 #endif