[RFC PATCH v2 6/6] RISC-V: selftests: Add DTSO tests

[Christoph Müllner <christoph.muellner@xxxxxxxx>]

This patch tests the dynamic memory consistency model prctl() behaviour
on RISC-V. It does not depend on CONFIG_RISCV_ISA_SSDTSO or the availability
of Ssdtso, but will test other aspects if these are not given.

Signed-off-by: Christoph Müllner <christoph.muellner@xxxxxxxx>
---
 tools/testing/selftests/riscv/Makefile        |  2 +-
 tools/testing/selftests/riscv/dtso/.gitignore |  1 +
 tools/testing/selftests/riscv/dtso/Makefile   | 11 +++
 tools/testing/selftests/riscv/dtso/dtso.c     | 82 +++++++++++++++++++
 4 files changed, 95 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/riscv/dtso/.gitignore
 create mode 100644 tools/testing/selftests/riscv/dtso/Makefile
 create mode 100644 tools/testing/selftests/riscv/dtso/dtso.c

diff --git a/tools/testing/selftests/riscv/Makefile b/tools/testing/selftests/riscv/Makefile
index 4a9ff515a3a0..1421c21841f9 100644
--- a/tools/testing/selftests/riscv/Makefile
+++ b/tools/testing/selftests/riscv/Makefile
@@ -5,7 +5,7 @@
 ARCH ?= $(shell uname -m 2>/dev/null || echo not)
 
 ifneq (,$(filter $(ARCH),riscv))
-RISCV_SUBTARGETS ?= hwprobe vector mm
+RISCV_SUBTARGETS ?= dtso hwprobe vector mm
 else
 RISCV_SUBTARGETS :=
 endif
diff --git a/tools/testing/selftests/riscv/dtso/.gitignore b/tools/testing/selftests/riscv/dtso/.gitignore
new file mode 100644
index 000000000000..217d01679115
--- /dev/null
+++ b/tools/testing/selftests/riscv/dtso/.gitignore
@@ -0,0 +1 @@
+dtso
diff --git a/tools/testing/selftests/riscv/dtso/Makefile b/tools/testing/selftests/riscv/dtso/Makefile
new file mode 100644
index 000000000000..a1ffbdd3da85
--- /dev/null
+++ b/tools/testing/selftests/riscv/dtso/Makefile
@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2023 VRULL
+
+CFLAGS += -I$(top_srcdir)/tools/include
+
+TEST_GEN_PROGS := dtso
+
+include ../../lib.mk
+
+$(OUTPUT)/dtso: dtso.c ../hwprobe/sys_hwprobe.S
+	$(CC) -static -o$@ $(CFLAGS) $(LDFLAGS) $^
diff --git a/tools/testing/selftests/riscv/dtso/dtso.c b/tools/testing/selftests/riscv/dtso/dtso.c
new file mode 100644
index 000000000000..c8a7b25adefd
--- /dev/null
+++ b/tools/testing/selftests/riscv/dtso/dtso.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* dtso - used for functional tests of memory consistency model switching
+ * at run-time.
+ *
+ * Copyright (c) 2023 Christoph Muellner <christoph.muellner@xxxxxxxx>
+ */
+
+#include <sys/prctl.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include "../hwprobe/hwprobe.h"
+#include "../../kselftest_harness.h"
+
+/*
+ * We have the following cases:
+ * 1) DTSO support disabed in the kernel config:
+ *    - Ssdtso is not detected
+ *    - {G,S}ET_MEMORY_CONSISTENCY_MODEL fails with EINVAL
+ * 2) DTSO support enabled and Ssdtso not available:
+ *    - Ssdtso is not detected
+ *    - {G,S}ET_MEMORY_CONSISTENCY_MODEL works for WMO and fails for TSO with EINVAL:
+ * 3) DTSO support enabled and Ssdtso available
+ *    - Ssdtso is detected
+ *    - {G,S}ET_MEMORY_CONSISTENCY_MODEL works for WMO and TSO
+ */
+
+TEST(dtso)
+{
+	struct riscv_hwprobe pair;
+	int ret;
+	bool ssdtso_configured;
+	bool ssdtso_available;
+
+	ret = prctl(PR_GET_MEMORY_CONSISTENCY_MODEL);
+	if (ret < 0) {
+		ASSERT_EQ(errno, EINVAL);
+		ssdtso_configured = false;
+	} else {
+		ASSERT_TRUE(ret == PR_MEMORY_CONSISTENCY_MODEL_RISCV_WMO ||
+			    ret == PR_MEMORY_CONSISTENCY_MODEL_RISCV_TSO);
+		ssdtso_configured = true;
+	}
+
+	pair.key = RISCV_HWPROBE_KEY_IMA_EXT_0;
+	ret = riscv_hwprobe(&pair, 1, 0, NULL, 0);
+	ASSERT_GE(ret, 0);
+	ASSERT_EQ(pair.key, RISCV_HWPROBE_KEY_IMA_EXT_0);
+	ssdtso_available = !!(pair.value & RISCV_HWPROBE_EXT_SSDTSO);
+
+	if (ssdtso_configured) {
+		/* Read out current model. */
+		ret = prctl(PR_GET_MEMORY_CONSISTENCY_MODEL);
+		ASSERT_TRUE(ret == PR_MEMORY_CONSISTENCY_MODEL_RISCV_WMO ||
+			    ret == PR_MEMORY_CONSISTENCY_MODEL_RISCV_TSO);
+
+		if (ssdtso_available) {
+			/* Switch to TSO. */
+			ret = prctl(PR_SET_MEMORY_CONSISTENCY_MODEL,
+				    PR_MEMORY_CONSISTENCY_MODEL_RISCV_TSO);
+			ASSERT_EQ(ret, 0);
+			ret = prctl(PR_GET_MEMORY_CONSISTENCY_MODEL);
+			ASSERT_TRUE(ret == PR_MEMORY_CONSISTENCY_MODEL_RISCV_TSO);
+
+			/* Try switching back to WMO (must fail). */
+			ret = prctl(PR_SET_MEMORY_CONSISTENCY_MODEL,
+				    PR_MEMORY_CONSISTENCY_MODEL_RISCV_WMO);
+			ASSERT_LT(ret, 0);
+			ret = prctl(PR_GET_MEMORY_CONSISTENCY_MODEL);
+			ASSERT_TRUE(ret == PR_MEMORY_CONSISTENCY_MODEL_RISCV_TSO);
+		} else {
+			/* Set the same model, that's currently active. */
+			ret = prctl(PR_SET_MEMORY_CONSISTENCY_MODEL, ret);
+			ASSERT_EQ(ret, 0);
+		}
+	} else {
+		ASSERT_EQ(ssdtso_available, false);
+		ksft_test_result_skip("Ssdtso not configured\n");
+	}
+}
+
+TEST_HARNESS_MAIN
-- 
2.43.0