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SubjectRe: [v3 03/12] x86/fsgsbase/64: Add intrinsics/macros for FSGSBASE instructions
On Tue, Oct 23, 2018 at 11:43 AM Chang S. Bae <> wrote:
> From: Andi Kleen <>
> Add C intrinsics and assembler macros for the new FSBASE and GSBASE
> instructions.
> Very straight forward. Used in followon patches.
> [ luto: Rename the variables from FS and GS to FSBASE and GSBASE and
> make <asm/fsgsbase.h> safe to include on 32-bit kernels. ]
> v2: Use __always_inline
> [ chang: Revise the changelog. Place them in <asm/fsgsbase.h>. Replace
> the macros with GAS-compatible ones. ]
> If GCC supports it, we can add -mfsgsbase to CFLAGS and use the builtins
> here for extra performance.

Reviewed-by: Andy Lutomirski <> # C parts only

With the caveat that I'm not convinced that the memory clobbers are
needed. The __force_order trick in special_insns.h would probably be
more appropriate.

I don't feel qualified to review the asm part without some research.
Whereas hpa or Boris could probably review it with their eyes closed.

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