[MODERATED] [PATCH 7/9] TAA 7

[Pawan Gupta <pawan.kumar.gupta@linux.intel.com>]

From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Subject: [PATCH 7/9] x86/tsx: Add "auto" option to the tsx= cmdline parameter

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

 [ bp: Extend the arg buffer to accommodate "auto\0". ]

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Paul E. McKenney" <paulmck@linux.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: linux-doc@vger.kernel.org
Cc: Mark Gross <mgross@linux.intel.com>
Cc: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
---
 Documentation/admin-guide/kernel-parameters.txt | 5 +++++
 arch/x86/kernel/cpu/tsx.c                       | 7 ++++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index ad6b69057bb0..e1aca10f2a7f 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4856,6 +4856,11 @@
 
 			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 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 e5933ef50add..89ab91eacd4f 100644
--- a/arch/x86/kernel/cpu/tsx.c
+++ b/arch/x86/kernel/cpu/tsx.c
@@ -69,7 +69,7 @@ static bool __init tsx_ctrl_is_supported(void)
 
 void __init tsx_init(void)
 {
-	char arg[4] = {};
+	char arg[5] = {};
 	int ret;
 
 	if (!tsx_ctrl_is_supported())
@@ -81,6 +81,11 @@ void __init tsx_init(void)
 			tsx_ctrl_state = TSX_CTRL_ENABLE;
 		} else if (!strcmp(arg, "off")) {
 			tsx_ctrl_state = TSX_CTRL_DISABLE;
+		} else if (!strcmp(arg, "auto")) {
+			if (boot_cpu_has_bug(X86_BUG_TAA))
+				tsx_ctrl_state = TSX_CTRL_DISABLE;
+			else
+				tsx_ctrl_state = TSX_CTRL_ENABLE;
 		} else {
 			tsx_ctrl_state = TSX_CTRL_DISABLE;
 			pr_err("tsx: invalid option, defaulting to off\n");
-- 
2.21.0