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Date: Thu, 13 Oct 2022 19:35:23 +0000 From: "Li, Xin3" <xin3.li@...el.com> To: "Bae, Chang Seok" <chang.seok.bae@...el.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "x86@...nel.org" <x86@...nel.org> CC: "tglx@...utronix.de" <tglx@...utronix.de>, "mingo@...hat.com" <mingo@...hat.com>, "bp@...en8.de" <bp@...en8.de>, "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>, "hpa@...or.com" <hpa@...or.com>, "peterz@...radead.org" <peterz@...radead.org> Subject: RE: [PATCH v2 1/6] x86/cpufeature: add cpu feature bit for LKGS > > diff --git a/arch/x86/include/asm/cpufeatures.h > > b/arch/x86/include/asm/cpufeatures.h > > index ef4775c6db01..459fb0c21dd4 100644 > > --- a/arch/x86/include/asm/cpufeatures.h > > +++ b/arch/x86/include/asm/cpufeatures.h > > @@ -308,6 +308,7 @@ > > /* Intel-defined CPU features, CPUID level 0x00000007:1 (EAX), word 12 */ > > #define X86_FEATURE_AVX_VNNI (12*32+ 4) /* AVX VNNI > instructions */ > > #define X86_FEATURE_AVX512_BF16 (12*32+ 5) /* AVX512 > BFLOAT16 instructions */ > > +#define X86_FEATURE_LKGS (12*32+ 18) /* Load "kernel" > (userspace) gs */ > > The spec says [1]: > "Execution of LKGS causes an invalid-opcode exception (#UD) if CPL > > 0." > > Perhaps userspace has no interest in this. Then, we can add "" not to show > "lkgs" in /proc/cpuinfo: > +#define X86_FEATURE_LKGS (12*32+ 18) /* "" Load "kernel" > (userspace) gs */ Good point! > > Thanks, > Chang > > [1] https://cdrdv2.intel.com/v1/dl/getContent/678938
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