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Message-ID: <CAKwvOdnj4M6xy3DhqE9U05bBhNEHR7-o8CM0T-KoQFRck0o39g@mail.gmail.com>
Date: Mon, 1 Jun 2020 12:47:25 -0700
From: Nick Desaulniers <ndesaulniers@...gle.com>
To: Brian Gerst <brgerst@...il.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
"H . Peter Anvin" <hpa@...or.com>,
Andy Lutomirski <luto@...nel.org>,
Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v2 06/10] x86/percpu: Clean up percpu_add_return_op()
On Sat, May 30, 2020 at 3:11 PM Brian Gerst <brgerst@...il.com> wrote:
>
> The core percpu macros already have a switch on the data size, so the switch
> in the x86 code is redundant and produces more dead code.
>
> Also use appropriate types for the width of the instructions. This avoids
> errors when compiling with Clang.
>
> Signed-off-by: Brian Gerst <brgerst@...il.com>
I think it would have been ok to carry forward my reviewed by tag here
from v1, hidden at the bottom of
https://lore.kernel.org/lkml/CAKwvOdn7yC1GVA+6gtNewBSq2BK09y9iNWhv1dPFF5i4kT1+6A@mail.gmail.com/
even though you split removing 'e' into it's own patch.
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
> ---
> arch/x86/include/asm/percpu.h | 51 +++++++++++------------------------
> 1 file changed, 16 insertions(+), 35 deletions(-)
>
> diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
> index 9bb5440d98d3..0776a11e7e11 100644
> --- a/arch/x86/include/asm/percpu.h
> +++ b/arch/x86/include/asm/percpu.h
> @@ -199,34 +199,15 @@ do { \
> /*
> * Add return operation
> */
> -#define percpu_add_return_op(qual, var, val) \
> +#define percpu_add_return_op(size, qual, _var, _val) \
> ({ \
> - typeof(var) paro_ret__ = val; \
> - switch (sizeof(var)) { \
> - case 1: \
> - asm qual ("xaddb %0, "__percpu_arg(1) \
> - : "+q" (paro_ret__), "+m" (var) \
> - : : "memory"); \
> - break; \
> - case 2: \
> - asm qual ("xaddw %0, "__percpu_arg(1) \
> - : "+r" (paro_ret__), "+m" (var) \
> - : : "memory"); \
> - break; \
> - case 4: \
> - asm qual ("xaddl %0, "__percpu_arg(1) \
> - : "+r" (paro_ret__), "+m" (var) \
> - : : "memory"); \
> - break; \
> - case 8: \
> - asm qual ("xaddq %0, "__percpu_arg(1) \
> - : "+r" (paro_ret__), "+m" (var) \
> - : : "memory"); \
> - break; \
> - default: __bad_percpu_size(); \
> - } \
> - paro_ret__ += val; \
> - paro_ret__; \
> + __pcpu_type_##size paro_tmp__ = __pcpu_cast_##size(_val); \
> + asm qual (__pcpu_op2_##size("xadd", "%[tmp]", \
> + __percpu_arg([var])) \
> + : [tmp] __pcpu_reg_##size("+", paro_tmp__), \
> + [var] "+m" (_var) \
> + : : "memory"); \
> + (typeof(_var))(unsigned long) (paro_tmp__ + _val); \
> })
>
> /*
> @@ -377,16 +358,16 @@ do { \
> #define this_cpu_xchg_2(pcp, nval) percpu_xchg_op(volatile, pcp, nval)
> #define this_cpu_xchg_4(pcp, nval) percpu_xchg_op(volatile, pcp, nval)
>
> -#define raw_cpu_add_return_1(pcp, val) percpu_add_return_op(, pcp, val)
> -#define raw_cpu_add_return_2(pcp, val) percpu_add_return_op(, pcp, val)
> -#define raw_cpu_add_return_4(pcp, val) percpu_add_return_op(, pcp, val)
> +#define raw_cpu_add_return_1(pcp, val) percpu_add_return_op(1, , pcp, val)
> +#define raw_cpu_add_return_2(pcp, val) percpu_add_return_op(2, , pcp, val)
> +#define raw_cpu_add_return_4(pcp, val) percpu_add_return_op(4, , pcp, val)
> #define raw_cpu_cmpxchg_1(pcp, oval, nval) percpu_cmpxchg_op(, pcp, oval, nval)
> #define raw_cpu_cmpxchg_2(pcp, oval, nval) percpu_cmpxchg_op(, pcp, oval, nval)
> #define raw_cpu_cmpxchg_4(pcp, oval, nval) percpu_cmpxchg_op(, pcp, oval, nval)
>
> -#define this_cpu_add_return_1(pcp, val) percpu_add_return_op(volatile, pcp, val)
> -#define this_cpu_add_return_2(pcp, val) percpu_add_return_op(volatile, pcp, val)
> -#define this_cpu_add_return_4(pcp, val) percpu_add_return_op(volatile, pcp, val)
> +#define this_cpu_add_return_1(pcp, val) percpu_add_return_op(1, volatile, pcp, val)
> +#define this_cpu_add_return_2(pcp, val) percpu_add_return_op(2, volatile, pcp, val)
> +#define this_cpu_add_return_4(pcp, val) percpu_add_return_op(4, volatile, pcp, val)
> #define this_cpu_cmpxchg_1(pcp, oval, nval) percpu_cmpxchg_op(volatile, pcp, oval, nval)
> #define this_cpu_cmpxchg_2(pcp, oval, nval) percpu_cmpxchg_op(volatile, pcp, oval, nval)
> #define this_cpu_cmpxchg_4(pcp, oval, nval) percpu_cmpxchg_op(volatile, pcp, oval, nval)
> @@ -418,7 +399,7 @@ do { \
> #define raw_cpu_add_8(pcp, val) percpu_add_op(8, , (pcp), val)
> #define raw_cpu_and_8(pcp, val) percpu_to_op(8, , "and", (pcp), val)
> #define raw_cpu_or_8(pcp, val) percpu_to_op(8, , "or", (pcp), val)
> -#define raw_cpu_add_return_8(pcp, val) percpu_add_return_op(, pcp, val)
> +#define raw_cpu_add_return_8(pcp, val) percpu_add_return_op(8, , pcp, val)
> #define raw_cpu_xchg_8(pcp, nval) raw_percpu_xchg_op(pcp, nval)
> #define raw_cpu_cmpxchg_8(pcp, oval, nval) percpu_cmpxchg_op(, pcp, oval, nval)
>
> @@ -427,7 +408,7 @@ do { \
> #define this_cpu_add_8(pcp, val) percpu_add_op(8, volatile, (pcp), val)
> #define this_cpu_and_8(pcp, val) percpu_to_op(8, volatile, "and", (pcp), val)
> #define this_cpu_or_8(pcp, val) percpu_to_op(8, volatile, "or", (pcp), val)
> -#define this_cpu_add_return_8(pcp, val) percpu_add_return_op(volatile, pcp, val)
> +#define this_cpu_add_return_8(pcp, val) percpu_add_return_op(8, volatile, pcp, val)
> #define this_cpu_xchg_8(pcp, nval) percpu_xchg_op(volatile, pcp, nval)
> #define this_cpu_cmpxchg_8(pcp, oval, nval) percpu_cmpxchg_op(volatile, pcp, oval, nval)
>
> --
> 2.25.4
>
--
Thanks,
~Nick Desaulniers
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