Re: [PATCH v7 18/21] x86/clearcpuid: Support feature flag string in kernel option clearcpuid

[Thomas Gleixner]

On Wed, 17 Apr 2019, Fenghua Yu wrote:
> On Thu, Apr 18, 2019 at 01:19:41AM +0200, Thomas Gleixner wrote:
> > On Wed, 17 Apr 2019, Fenghua Yu wrote:
> > 
> > > The kernel option clearcpuid currently only takes feature bit which
> > > can be changed from kernel to kernel.
> > > 
> > > Extend clearcpuid to use cap flag string, which is defined in
> > > x86_cap_flags[] and won't be changed from kernel to kernel.
> > > And user can easily get the cap flag string from /proc/cpuinfo.
> > 
> > If your machine dies because init triggers #AC then please explain how that
> > easily can be read from /proc/cpuinfo and how the sysadmin can figure out
> > what the heck he needs to write on the kernel command line.
> > 
> > The whole 'clearcpuid' thing should have never been merged. It's a pure
> > testing/debugging thing. And no, we are not going to proliferate it and
> > extend it for dubious value. Quite the contrary, we should simply rip it
> > out.
> 
> So I can remove the four 'clearcpuid' related patches 0018-0021 in the next
> version, right?

Yes please. They are unrelated to this problem and 'noac' is way more admin
friendly than that.

Thanks,

	tglx