Re: [PATCH v5 04/13] x86/fsgsbase/64: Add intrinsics for FSGSBASE instructions

From: Andy Lutomirski
Date: Fri Feb 01 2019 - 21:52:50 EST

On Fri, Feb 1, 2019 at 12:54 PM Chang S. Bae <chang.seok.bae@xxxxxxxxx> wrote:
> From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> 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

Does it really get better performance? If so, let's do it. If not,
let's remove the comment. And, whatever you do, please put this above
the [luto] and [chang] parts.
> [ chang: Use FSGSBASE instructions directly. Removed GAS-compatible
> macros as the minimum required binutils (v2.21) supports the FSGSBASE
> instructions. ]

Can you stick the "v2" revision notes below the --- or even just
remove them? It makes the changelog a lot harder to review and it's
not really useful in the git tree.