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>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index af4b1d95b08f..6e548cddb6c3 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4869,6 +4869,9 @@
                                 update. This new MSR allows for the reliable
                                 deactivation of the TSX functionality.)
 
+                        auto    - Disable TSX if X86_BUG_TAA is present,
+                                  otherwise enable TSX on the system.
+
                         Not specifying this option is equivalent to tsx=off.
 
                         See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst