Use early_param() to get the value of the tsx= command line parameter.
Although cmdline_find_option() works fine, the option is later reported
as unknown and passed to user space. The latter is not a real issue, but
the former is confusing and makes people wonder if the tsx= parameter had
any effect and double-check for typos unnecessarily.

The behavior changes slightly if "tsx" is given without any argument (which
is invalid syntax). Prior to this patch, the kernel logged an error message
and disabled TSX. With this patch, the parameter is ignored. The new
behavior is consistent with other parameters, e.g. "tsx_async_abort".

Signed-off-by: Petr Tesarik <ptesarik@suse.com>
---
 arch/x86/kernel/cpu/tsx.c | 41 ++++++++++++++++++++++-----------------
 1 file changed, 23 insertions(+), 18 deletions(-)

diff --git a/arch/x86/kernel/cpu/tsx.c b/arch/x86/kernel/cpu/tsx.c
index 167dfd38b87a2..bb407331f64b5 100644
--- a/arch/x86/kernel/cpu/tsx.c
+++ b/arch/x86/kernel/cpu/tsx.c
@@ -20,14 +20,14 @@
 #define pr_fmt(fmt) "tsx: " fmt
 
 enum tsx_ctrl_states {
+	TSC_CTRL_UNSPECIFIED,
 	TSX_CTRL_ENABLE,
 	TSX_CTRL_DISABLE,
 	TSX_CTRL_RTM_ALWAYS_ABORT,
 	TSX_CTRL_NOT_SUPPORTED,
 };
 
-static enum tsx_ctrl_states tsx_ctrl_state __ro_after_init =
-	TSX_CTRL_NOT_SUPPORTED;
+static enum tsx_ctrl_states tsx_ctrl_state __ro_after_init;
 
 static void tsx_disable(void)
 {
@@ -164,11 +164,28 @@ static void tsx_dev_mode_disable(void)
 	}
 }
 
-void __init tsx_init(void)
+static int __init tsx_parse_cmdline(char *str)
 {
-	char arg[5] = {};
-	int ret;
+	if (!str)
+		return -EINVAL;
+
+	if (!strcmp(str, "on")) {
+		tsx_ctrl_state = TSX_CTRL_ENABLE;
+	} else if (!strcmp(str, "off")) {
+		tsx_ctrl_state = TSX_CTRL_DISABLE;
+	} else if (!strcmp(str, "auto")) {
+		tsx_ctrl_state = x86_get_tsx_auto_mode();
+	} else {
+		tsx_ctrl_state = TSX_CTRL_DISABLE;
+		pr_err("invalid option, defaulting to off\n");
+	}
 
+	return 0;
+}
+early_param("tsx", tsx_parse_cmdline);
+
+void __init tsx_init(void)
+{
 	tsx_dev_mode_disable();
 
 	/*
@@ -202,19 +219,7 @@ void __init tsx_init(void)
 		return;
 	}
 
-	ret = cmdline_find_option(boot_command_line, "tsx", arg, sizeof(arg));
-	if (ret >= 0) {
-		if (!strcmp(arg, "on")) {
-			tsx_ctrl_state = TSX_CTRL_ENABLE;
-		} else if (!strcmp(arg, "off")) {
-			tsx_ctrl_state = TSX_CTRL_DISABLE;
-		} else if (!strcmp(arg, "auto")) {
-			tsx_ctrl_state = x86_get_tsx_auto_mode();
-		} else {
-			tsx_ctrl_state = TSX_CTRL_DISABLE;
-			pr_err("invalid option, defaulting to off\n");
-		}
-	} else {
+	if (tsx_ctrl_state == TSC_CTRL_UNSPECIFIED) {
 		/* tsx= not provided */
 		if (IS_ENABLED(CONFIG_X86_INTEL_TSX_MODE_AUTO))
 			tsx_ctrl_state = x86_get_tsx_auto_mode();
-- 
2.50.1