lkml.org 
[lkml]   [2018]   [Mar]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] clarify how insecure CPU is
On Sun 2018-03-04 10:29:18, Borislav Petkov wrote:
> On Sun, Mar 04, 2018 at 09:51:59AM +0100, Pavel Machek wrote:
> > diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> > index f41079d..4901742 100644
> > --- a/arch/x86/include/asm/cpufeatures.h
> > +++ b/arch/x86/include/asm/cpufeatures.h
> > @@ -341,7 +341,7 @@
> > #define X86_BUG_FDIV X86_BUG(1) /* FPU FDIV */
> > #define X86_BUG_COMA X86_BUG(2) /* Cyrix 6x86 coma */
> > #define X86_BUG_AMD_TLB_MMATCH X86_BUG(3) /* "tlb_mmatch" AMD Erratum 383 */
> > -#define X86_BUG_AMD_APIC_C1E X86_BUG(4) /* "apic_c1e" AMD Erratum 400 */
> > +#define X86_BUG_AMD_APIC_C1E X86_BUG(4) /* System is affected AMD Erratum 400, special idle routine is needed */
> > #define X86_BUG_11AP X86_BUG(5) /* Bad local APIC aka 11AP */
> > #define X86_BUG_FXSAVE_LEAK X86_BUG(6) /* FXSAVE leaks FOP/FIP/FOP */
> > #define X86_BUG_CLFLUSH_MONITOR X86_BUG(7) /* AAI65, CLFLUSH required before MONITOR */
> > @@ -356,7 +356,7 @@
> > #define X86_BUG_NULL_SEG X86_BUG(10) /* Nulling a selector preserves the base */
> > #define X86_BUG_SWAPGS_FENCE X86_BUG(11) /* SWAPGS without input dep on GS */
> > #define X86_BUG_MONITOR X86_BUG(12) /* IPI required to wake up remote CPU */
> > -#define X86_BUG_AMD_E400 X86_BUG(13) /* CPU is among the affected by Erratum 400 */
> > +#define X86_BUG_AMD_E400 X86_BUG(13) /* System may be affected by Erratum 400, X86_BUG_AMD_APIC_C1E might be needed */
>
> Not "might be needed" - "X86_BUG_AMD_APIC_C1E will be set if platform is
> affected".

That's not what Thomas was explaining to me.

> And then you don't need the above comment change. And you can't remove
> "apic_c1e" there because it is magical.

So.. what's magical about it, why do we need two bits, and why is that
not explained in the header file?

Please go through the email thread, I'm trying to understand what is
going on here, and no, the comments in the header are not helpful.

--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
[unhandled content-type:application/pgp-signature]
\
 
 \ /
  Last update: 2018-03-04 15:02    [W:0.042 / U:8.160 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site