[PATCH 3/3] tests: Add test for ASID2 and write/read of feature bits

[Jim MacArthur <jim.macarthur@linaro.org>]

Tests ASID2 is present and FNG1, FNG0, and A2 are writable, and read
value shows the update.

Signed-off-by: Jim MacArthur <jim.macarthur@linaro.org>
---
 tests/tcg/aarch64/system/asid2.c | 53 ++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)
 create mode 100644 tests/tcg/aarch64/system/asid2.c

diff --git a/tests/tcg/aarch64/system/asid2.c b/tests/tcg/aarch64/system/asid2.c
new file mode 100644
index 0000000000..cfe69db2ae
--- /dev/null
+++ b/tests/tcg/aarch64/system/asid2.c
@@ -0,0 +1,53 @@
+/*
+ * ASID2 Feature presence and enabled TCR2_EL1 bits test
+ *
+ * Copyright (c) 2025 Linaro Ltd
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include <stdint.h>
+#include <minilib.h>
+
+#define ID_AA64MMFR4_EL1 "S3_0_C0_C7_4"
+#define TCR2_EL1 "S3_0_C2_C0_3"
+
+int main()
+{
+    /*
+     * Test for presence of ASID2 and three feature bits enabled by it:
+     * https://developer.arm.com/documentation/109697/2025_09/Feature-descriptions/The-Armv9-5-architecture-extension
+     * Bits added are FNG1, FNG0, and A2. These should be RES0 if A2 is
+     * not enabled and read as the written value if A2 is enabled.
+     */
+
+    uint64_t out;
+    uint64_t idreg;
+
+    /* Mask is FNG1, FNG0, and A2 */
+    const uint64_t feature_mask = (1ULL << 18 | 1ULL << 17 | 1ULL << 16);
+    const uint64_t in = feature_mask;
+
+    asm("mrs %[x1], " ID_AA64MMFR4_EL1 "\n\t"
+        : [x1] "=r" (idreg));
+    if ((idreg & 0xF00) != 0) {
+        /* ASID2 is enabled */
+    } else {
+        ml_printf("FAIL: ASID2 not present in ID_AA64MMFR4 (%lx)\n", idreg);
+        return 1;
+    }
+
+    asm("msr " TCR2_EL1 ", %[x0]\n\t"
+        "mrs %[x1], " TCR2_EL1 "\n\t"
+        : [x1] "=r" (out)
+        : [x0] "r" (in));
+
+    if ((out & feature_mask) == in) {
+        ml_printf("OK\n");
+        return 0;
+    } else {
+        ml_printf("FAIL: read value %lx != written value %lx\n",
+                  out & feature_mask, in);
+        return 1;
+    }
+}
-- 
2.43.0