[PATCHv16 17/17] selftests/x86/lam: Add test cases for LAM vs thread creation

[Kirill A. Shutemov]

LAM enabling is only allowed when the process has single thread.
LAM mode is inherited into child thread.

Trying to enable LAM after spawning a thread has to fail.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 tools/testing/selftests/x86/lam.c | 92 +++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)

diff --git a/tools/testing/selftests/x86/lam.c b/tools/testing/selftests/x86/lam.c
index a8c91829b616..eb0e46905bf9 100644
--- a/tools/testing/selftests/x86/lam.c
+++ b/tools/testing/selftests/x86/lam.c
@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -12,6 +13,7 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <inttypes.h>
+#include <sched.h>
 
 #include <sys/uio.h>
 #include <linux/io_uring.h>
@@ -50,6 +52,8 @@
 
 #define PAGE_SIZE               (4 << 10)
 
+#define STACK_SIZE		65536
+
 #define barrier() ({						\
 		   __asm__ __volatile__("" : : : "memory");	\
 })
@@ -731,6 +735,75 @@ static int handle_inheritance(struct testcases *test)
 	return 0;
 }
 
+static int thread_fn_get_lam(void *arg)
+{
+	return get_lam();
+}
+
+static int thread_fn_set_lam(void *arg)
+{
+	struct testcases *test = arg;
+
+	return set_lam(test->lam);
+}
+
+static int handle_thread(struct testcases *test)
+{
+	char stack[STACK_SIZE];
+	int ret, child_ret;
+	int lam = 0;
+	pid_t pid;
+
+	/* Set LAM mode in parent process */
+	if (!test->later) {
+		lam = test->lam;
+		if (set_lam(lam) != 0)
+			return 1;
+	}
+
+	pid = clone(thread_fn_get_lam, stack + STACK_SIZE,
+		    SIGCHLD | CLONE_FILES | CLONE_FS | CLONE_VM, NULL);
+	if (pid < 0) {
+		perror("Clone failed.");
+		return 1;
+	}
+
+	waitpid(pid, &child_ret, 0);
+	ret = WEXITSTATUS(child_ret);
+
+	if (lam != ret)
+		return 1;
+
+	if (test->later) {
+		if (set_lam(test->lam) != 0)
+			return 1;
+	}
+
+	return 0;
+}
+
+static int handle_thread_enable(struct testcases *test)
+{
+	char stack[STACK_SIZE];
+	int ret, child_ret;
+	int lam = test->lam;
+	pid_t pid;
+
+	pid = clone(thread_fn_set_lam, stack + STACK_SIZE,
+		    SIGCHLD | CLONE_FILES | CLONE_FS | CLONE_VM, test);
+	if (pid < 0) {
+		perror("Clone failed.");
+		return 1;
+	}
+
+	waitpid(pid, &child_ret, 0);
+	ret = WEXITSTATUS(child_ret);
+
+	if (lam != ret)
+		return 1;
+
+	return 0;
+}
 static void run_test(struct testcases *test, int count)
 {
 	int i, ret = 0;
@@ -846,6 +919,25 @@ static struct testcases inheritance_cases[] = {
 		.test_func = handle_inheritance,
 		.msg = "FORK: LAM_U57, child process should get LAM mode same as parent\n",
 	},
+	{
+		.expected = 0,
+		.lam = LAM_U57_BITS,
+		.test_func = handle_thread,
+		.msg = "THREAD: LAM_U57, child thread should get LAM mode same as parent\n",
+	},
+	{
+		.expected = 1,
+		.lam = LAM_U57_BITS,
+		.test_func = handle_thread_enable,
+		.msg = "THREAD: [NEGATIVE] Enable LAM in child.\n",
+	},
+	{
+		.expected = 1,
+		.later = 1,
+		.lam = LAM_U57_BITS,
+		.test_func = handle_thread,
+		.msg = "THREAD: [NEGATIVE] Enable LAM in parent after thread created.\n",
+	},
 	{
 		.expected = 0,
 		.lam = LAM_U57_BITS,
-- 
2.39.2