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SubjectRe: [PATCH 29/35] x86/speculation: Add IPBP support
On Thu, Jan 18, 2018 at 07:31:16PM +0100, Borislav Petkov wrote:
> On Thu, Jan 18, 2018 at 02:48:29PM +0100, Peter Zijlstra wrote:
> > From: Thomas Gleixner <tglx@linutronix.de>
>
> <--- Add commit message here.
>
> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > ---
> > arch/x86/include/asm/cpufeatures.h | 4 +++-
> > arch/x86/include/asm/msr-index.h | 3 +++
> > arch/x86/include/asm/nospec-branch.h | 9 +++++++++
> > arch/x86/kernel/cpu/bugs.c | 2 ++
> > arch/x86/kernel/cpu/specctrl.c | 9 +++++++++
> > 5 files changed, 26 insertions(+), 1 deletion(-)
> >
> > --- a/arch/x86/include/asm/cpufeatures.h
> > +++ b/arch/x86/include/asm/cpufeatures.h
> > @@ -212,8 +212,9 @@
> >
> > #define X86_FEATURE_MBA ( 7*32+18) /* Memory Bandwidth Allocation */
> > #define X86_FEATURE_RSB_CTXSW ( 7*32+19) /* Fill RSB on context switches */
> > -#define X86_FEATURE_SPEC_CTRL ( 7*32+20) /* Speculation Control */
> > +#define X86_FEATURE_SPEC_CTRL ( 7*32+20) /* Speculation Control - Intel only */
> > #define X86_FEATURE_IBRS ( 7*32+21) /* Indirect Branch Restricted Speculation */
> > +#define X86_FEATURE_IBPB ( 7*32+22) /* Indirect Branch Prediction Barrier */
> >
> > /* Virtualization flags: Linux defined, word 8 */
> > #define X86_FEATURE_TPR_SHADOW ( 8*32+ 0) /* Intel TPR Shadow */
> > @@ -273,6 +274,7 @@
> > #define X86_FEATURE_CLZERO (13*32+ 0) /* CLZERO instruction */
> > #define X86_FEATURE_IRPERF (13*32+ 1) /* Instructions Retired Count */
> > #define X86_FEATURE_XSAVEERPTR (13*32+ 2) /* Always save/restore FP error pointers */
> > +#define X86_FEATURE_AMD_IBPB (13*32+12) /* Indirect Branch Prediction Barrier support */
>
> I guess you could make that
>
> #define X86_FEATURE_AMD_IBPB (13*32+12) /* "" Indirect Branch Prediction Barrier support */
>
> (note the "" in the comment)
>
> so that it doesn't appear in /proc/cpuinfo as those two flags denote the
> same thing.

Maybe I missed the memo, why do we need both X86_FEATURE_IBPB and
X86_FEATURE_AMD_IBPB?

--
Josh

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