[MODERATED] Re: ***UNCHECKED*** Re: [PATCH v5 08/11] TAAv5 8

On Tue, 15 Oct 2019, speck for Josh Poimboeuf wrote:

> Maybe I'm missing something.  Isn't there going to be a ucode update for
> MDS_NO parts, which does the verw buffer clearing?  In that case there's
> no need to disable TSX, and instead the verw mitigation could be used,
> if desired.

My understanding was that MDS_NO CPUs will only get ucode update that 
exposes TSX control MSR, and nothing else.

> AFAICT, the patch allows to set the default to tsx=auto, which disables 
> TSX on *all* vulnerable parts, not just the MDS_NO ones.  I don't see 
> how that would prevent user regressions.
> 
> It sounds like maybe you're suggesting something else, that TSX should
> only be disabled on vulnerable MDS_NO parts?

OK, let me take a look at the code again. I definitely thought that's what 
'auto' indeed does.

-- 
Jiri Kosina
SUSE Labs