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

On Thu, Oct 24, 2019 at 06:33:36PM +0200, speck for Borislav Petkov wrote:
> 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?

ACK

-- 
Josh