Re: [PATCH 4.19 72/98] x86/CPU/AMD: Clear RDRAND CPUID bit on AMD family 15h/16h

Pavel Machek
2019-08-28T22:05:40Z

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On Wed 2019-08-28 16:15:06, Thomas Gleixner wrote:
> On Wed, 28 Aug 2019, Pavel Machek wrote:
> > On Wed 2019-08-28 14:46:21, Borislav Petkov wrote:
> > > On Wed, Aug 28, 2019 at 02:29:13PM +0200, Pavel Machek wrote:
> > > > This is not a way to have an inteligent conversation.
> > >
> > > No, this *is* the way to keep the conversation sane, without veering
> > > off into some absurd claims.
> > >
> > > So, to cut to the chase: you can simply add "rdrand=force" to your
> > > cmdline parameters and get back to using RDRAND.
> > >
> > > And yet if you still feel this fix does not meet your expectations,
> > > you were told already to either produce patches or who to contact. I'm
> > > afraid complaining on this thread won't get you anywhere but that's your
> > > call.
> >
> > No, this does not meet my expectations, it violates stable kernel
> > rules, and will cause regression to some users, while better solution
> > is known to be available.
>
> Your unqualified ranting does not meet my expectation either and it
> violates any rule of common sense.
>
> For the record:
>
> Neither AMD nor we have any idea which particular machines have a fixed
> BIOS and which have not. There is no technical indicator either at boot
> time as the wreckage manifests itself only after resume.
>
> So in the interest of users the only sensible decision is to disable
> RDRAND for this class of CPUs.

No.

Obviously best solution would be microcode update to fix the problem,
or to enable kernel to fix the problem.

> If you have a list of machines which have a fixed BIOS, then provide it
> in form of patches. If not then stop claiming that there is a better
> solution available.

And yes, whitelist would be already better than present solution. It is
not my duty to submit fixes to your proposed patch.

> Anyway, I'm done with that and further rants of yours go directly to
> /dev/null.
>
> Thanks for wasting everyones time

Thanks for your profesional attitude.

Pavel
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