Re: [patch V5 09/14] MDS basics 9

On Fri, 1 Mar 2019, speck for Andrea Arcangeli wrote:
> On Fri, Mar 01, 2019 at 08:15:36PM +0100, speck for Thomas Gleixner wrote:
> > > Also it sounds like the mds vulnerabilities file shouldn't ever show
> > > "SMT vulnerable" for XEON PHI.
> > 
> > Yeah.
> 
> So maybe this patch should be moved to the end of the series flagged
> as an incremental XEON PHI optimization by also adding the other XEON
> PHI specific change for the l1tf default mitigation and the respective
> alteration of the vulnerabilities mds/l1tf sysfs file outputs.
> 
> Is the verw measurable before mwait/hlt? I was just afraid this could
> hurt who needs to keep HT on for performance reasons and that won't be
> safe anyway if HT is kept on.
> 
> Unless we also alter the vulnerabilites file like Josh suggested, XEON
> PHI owners not reading the fineprint (assuming it's reachable for
> them) may decide then to disable HT for security reasons anyway and
> they won't even benefit from the XEON PHI mwait/hlt specific static
> key to keep HT enabled safely.

I already did those changes to the sysfs file and updated documentation
accordingly. Will send an updated series soon.

> > So I was looking at that table again and found the following stepping
> > related info:
> > 
> > 06_8EH,06_9EH	<=B	Kaby/Coffe Lake		Yes Yes Yes Yes
> > 06_9E		0xC	Coffee Lake		No  Yes Yes Yes
> > 06_8E		0xB	Whiskey Lake(ULT)	No  Yes	Yes Yes
> > 
> > 06_8E		0xC	Whiskey L (ULT refresh) No  No  No  No
> > 06_9E		0xD	Whiskey Lake (Deskto)   No  No  No  No
> > 
> > 
> > 06_55H		5	Cascade Lake		No  Yes Yes Yes
> > 
> > 06_55H		6	Cascade Lake		No  No  No  No
> > 
> > Will these 'fixed' steppings have MDS_NO set?
> 
> I couldn't understand the table, so I'm can't answer this one.

Sorry I dropped the first line:

Family_model, Stepping, Codename, MFBDS, MSBDS, MLPDS Vector, MLPDS Split line.

So the thing is that newer steppings are fixed vs. all of the issues. I
surely hope that these have MDS_NO set in MSR_IA32_ARCH_CAPABILITIES.

If that's not the case, then we'll end up with stepping specific quirks
which would be an utter mess.

Can anyone @Intel please answer this question?

Thanks,

	tglx