On 01/23/2018 05:23 PM, Woodhouse, David wrote: > On Tue, 2018-01-23 at 10:43 -0800, Dave Hansen wrote: ... >>> /* Intel-defined CPU features, CPUID level 0x00000007:0 (EDX), word 18 */ >>> #define X86_FEATURE_AVX512_4VNNIW (18*32+ 2) /* AVX-512 Neural Network >>> Instructions */ >>> #define X86_FEATURE_AVX512_4FMAPS (18*32+ 3) /* AVX-512 Multiply >>> Accumulation Single precision */ >>> +#define X86_FEATURE_SPEC_CTRL (18*32+26) /* Speculation >>> Control (IBRS + IBPB) */ >>> +#define X86_FEATURE_STIBP (18*32+27) /* Single Thread Indirect >>> Branch Predictors */ >>> +#define X86_FEATURE_ARCH_CAPABILITIES (18*32+29) /* >>> IA32_ARCH_CAPABILITIES MSR (Intel) */ >> Should we be adding flags (STIBP) for which we currently have no user in >> the kernel? > They're in an existing word (now) so it costs us absolutely nothing to > do so. And they'll be exposed to KVM guests in imminent patches if > nothing else.
Doesn't just defining it here generate something in the tables that then get exported in /proc/cpuinfo? That's far from our most strict ABI, but a single #define here can be seen by users IIRC.
