[MODERATED] [PATCH v5 08/11] TAAv5 8

Platforms which are not affected by X86_BUG_TAA may want the TSX feature
enabled. Add "auto" option to the TSX cmdline parameter. When tsx=auto,
disable TSX when X86_BUG_TAA is present, otherwise enable TSX.

More details on X86_BUG_TAA can be found here:
https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/tsx_async_abort.html

Signed-off-by: Pawan Gupta <[email protected]>
Reviewed-by: Tony Luck <[email protected]>
Tested-by: Neelima Krishnan <[email protected]>
---
 Documentation/admin-guide/kernel-parameters.txt | 5 +++++
 arch/x86/kernel/cpu/tsx.c                       | 9 +++++++++
 2 files changed, 14 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 832537d59562..d7b48c38c6e5 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4821,6 +4821,11 @@
 
 			on	- Enable TSX on the system.
 			off	- Disable TSX on the system.
+			auto	- Disable TSX if X86_BUG_TAA is present,
+				  otherwise enable TSX on the system.
+
+			More details on X86_BUG_TAA are here:
+			Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
 
 			Not specifying this option is equivalent to tsx=off.
 
diff --git a/arch/x86/kernel/cpu/tsx.c b/arch/x86/kernel/cpu/tsx.c
index 1c0cee7a7d46..73a0e5af3720 100644
--- a/arch/x86/kernel/cpu/tsx.c
+++ b/arch/x86/kernel/cpu/tsx.c
@@ -23,6 +23,7 @@ static enum tsx_user_cmds {
 	TSX_USER_CMD_NONE,
 	TSX_USER_CMD_ON,
 	TSX_USER_CMD_OFF,
+	TSX_USER_CMD_AUTO,
 } tsx_user_cmd = TSX_USER_CMD_NONE;
 
 static int __init tsx_cmdline(char *str)
@@ -38,6 +39,8 @@ static int __init tsx_cmdline(char *str)
 		tsx_user_cmd = TSX_USER_CMD_ON;
 	else if (!strcmp(str, "off"))
 		tsx_user_cmd = TSX_USER_CMD_OFF;
+	else if (!strcmp(str, "auto"))
+		tsx_user_cmd = TSX_USER_CMD_AUTO;
 
 	return 0;
 }
@@ -104,6 +107,12 @@ void tsx_init(struct cpuinfo_x86 *c)
 	case TSX_USER_CMD_OFF:
 		tsx_ctrl_state = TSX_CTRL_DISABLE;
 		break;
+	case TSX_USER_CMD_AUTO:
+		if (boot_cpu_has_bug(X86_BUG_TAA))
+			tsx_ctrl_state = TSX_CTRL_DISABLE;
+		else
+			tsx_ctrl_state = TSX_CTRL_ENABLE;
+		break;
 	case TSX_USER_CMD_NONE:
 	default:
 		/*
-- 
2.20.1