On 09/30/2014 09:51 PM, Andy Lutomirski wrote: > > diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S > index 4299eb05023c..44d1dd371454 100644 > --- a/arch/x86/ia32/ia32entry.S > +++ b/arch/x86/ia32/ia32entry.S > @@ -151,6 +151,18 @@ ENTRY(ia32_sysenter_target) > 1: movl (%rbp),%ebp > _ASM_EXTABLE(1b,ia32_badarg) > ASM_CLAC > + > + /* > + * Sysenter doesn't filter flags, so we need to clear NT > + * ourselves. To save a few cycles, we can check whether > + * NT was set instead of doing an unconditional popfq. > + */ > + testl $X86_EFLAGS_NT,EFLAGS(%rsp) /* saved EFLAGS match cpu */ > + jz 1f > + pushq_cfi $(X86_EFLAGS_IF|X86_EFLAGS_FIXED) > + popfq_cfi > +1: > + I'm wondering if it would be easier to just remove ASM_CLAC and do this unconditionally. On SMAP-enabled hardware then that gives us back some of the cycles, may make the branch unnecessary. -hpa -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html