[MODERATED] Re: [PATCH 3/9] TAA 3

On Wed, Oct 23, 2019 at 11:01:53AM +0200, speck for Pawan Gupta wrote:
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -4848,6 +4848,17 @@
>  			interruptions from clocksource watchdog are not
>  			acceptable).
>  
> +	tsx=		[X86] Control Transactional Synchronization
> +			Extensions (TSX) feature in Intel processors that
> +			support TSX control.
> +
> +			This parameter controls the TSX feature. The options are:
> +
> +			on	- Enable TSX on the system.
> +			off	- Disable TSX on the system.
> +
> +			Not specifying this option is equivalent to tsx=off.

This still needs details about when 'tsx=off' does and doesn't work.

The above makes it sound like it's off for all CPUs, when in fact it's
only off for newer MDS_NO CPUs.

It should also perhaps describe the risks associated with tsx=on.  While
there are mitigations for all known issues (i.e., the tsx_async_abort=
option), TSX has been known to be an accelerator for several previous
speculation-related CVEs, and so there may be unknown security risks
associated with leaving it enabled.

-- 
Josh