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

On Thu, Oct 24, 2019 at 10:30:15AM -0500, speck for Josh Poimboeuf wrote:
> 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.

How does that sound (and that is being mentioned somewhere in all the
text but here it is important to have):

			off     - Disable TSX on the system. (Note that this
				option takes effect only on newer CPUs which are
				not vulnerable to MDS, i.e., have
				MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
				the new IA32_TSX_CTRL MSR through a microcode
				update. This new MSR allows for the reliable
				deactivation of the TSX functionality.)

> 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.

You've basically said it nicely already:

"Although there are mitigations for all known security vulnerabilities,
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."

ACK?

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    Boris.

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