From: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx> commit 7531a3596e3272d1f6841e0d601a614555dc6b65 upstream. 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@xxxxxxxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx> Reviewed-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> [bwh: Backported to 4.4: adjust filename] Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- Documentation/kernel-parameters.txt | 3 +++ arch/x86/kernel/cpu/tsx.c | 7 ++++++- 2 files changed, 9 insertions(+), 1 deletion(-) --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -4073,6 +4073,9 @@ bytes respectively. Such letter suffixes 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/hw-vuln/tsx_async_abort.rst --- a/arch/x86/kernel/cpu/tsx.c +++ b/arch/x86/kernel/cpu/tsx.c @@ -75,7 +75,7 @@ static bool __init tsx_ctrl_is_supported void __init tsx_init(void) { - char arg[4] = {}; + char arg[5] = {}; int ret; if (!tsx_ctrl_is_supported()) @@ -87,6 +87,11 @@ 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");
