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

On Wed, Oct 16, 2019 at 02:15:08PM +0200, speck for Thomas Gleixner wrote:
> On Wed, 16 Oct 2019, speck for Michal Hocko wrote:
> > On Wed 16-10-19 09:54:34, speck for Michal Hocko wrote:
> > [...]
> > > +config X86_INTEL_TSX_MODE_OFF
> > > +	bool "off"
> > > +	help
> > > +	  TSX is always disabled - equals tsx=off command line parameter.
> > > +
> > > +config X86_INTEL_TSX_MODE_ON
> > > +	bool "on"
> > > +	help
> > > +	  TSX is always enabled on TSX capable HW - equals tsx=on command line
> > > +	  parameter.
> > > +
> > > +config X86_INTEL_TSX_MODE_AUTO
> > > +	bool "auto"
> > > +	help
> > > +	  TSX is enabled on TSX capable HW that is believed to be safe against
> > > +	  side channel attacks- equals tsx=auto command line parameter.
> > > +endchoice
> > 
> > I have just reread the discussion again and I have to say that there is
> > more confusion and uncertainty than I would like to see. Can somebody
> > from Intel give an authoritative answer to the following question
> > please?
> > 
> > Is tsx=auto going to lead to any different state than tsx=on? In other
> > words does auto mode make any sense at all?
> 
> Is it only my vacation induced spark of mental sanity or is this whole TAA
> thing a complete trainwreck again?
> 
> We're at version 5 and more than 3 month since the first RFC got posted and
> we are still debating which CPUs are affected and which migitations are
> going to be deployed depending on the CPU advertized misfeatures and the
> eventually surfacing microcode?
> 
> Can we please stop this complete waste of time right now and start over
> with clarifying the situation? I.e. someone at Intel needs to sit down and
> write up a matrix:
> 
> TAA-Affected | MDS_NO | VERW works | TSX_MSR | Resulting action
> -------------|--------|------------|---------|-----------------
>  No          |   X    |     X      |    Y    | ?
>  No          |   X    |     X      |    N    | None
>  Yes         |   0    |     0      |    0    | SNAFU
>  ...         |        |            |         |
> 
> You surely can fill in the rest on your own, right?
> 
> And exactly that information wants to be in the admin documentation or in a
> separate Documentation/x86/taa.rst as well.

I am working on this with other folks at Intel.

Thanks,
Pawan