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Date: Mon, 18 May 2020 14:27:23 -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 3/7] x86/percpu: Clean up percpu_from_op()
On Sun, May 17, 2020 at 8:29 AM 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>
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
> ---
> arch/x86/include/asm/percpu.h | 50 +++++++++++------------------------
> 1 file changed, 15 insertions(+), 35 deletions(-)
>
> diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
> index 233c7a78d1a6..93f33202492d 100644
> --- a/arch/x86/include/asm/percpu.h
> +++ b/arch/x86/include/asm/percpu.h
> @@ -190,33 +190,13 @@ do { \
> } \
> } while (0)
>
> -#define percpu_from_op(qual, op, var) \
> -({ \
> - typeof(var) pfo_ret__; \
> - switch (sizeof(var)) { \
> - case 1: \
> - asm qual (op "b "__percpu_arg(1)",%0" \
> - : "=q" (pfo_ret__) \
> - : "m" (var)); \
> - break; \
> - case 2: \
> - asm qual (op "w "__percpu_arg(1)",%0" \
> - : "=r" (pfo_ret__) \
> - : "m" (var)); \
> - break; \
> - case 4: \
> - asm qual (op "l "__percpu_arg(1)",%0" \
> - : "=r" (pfo_ret__) \
> - : "m" (var)); \
> - break; \
> - case 8: \
> - asm qual (op "q "__percpu_arg(1)",%0" \
> - : "=r" (pfo_ret__) \
> - : "m" (var)); \
> - break; \
> - default: __bad_percpu_size(); \
> - } \
> - pfo_ret__; \
> +#define percpu_from_op(size, qual, op, _var) \
> +({ \
> + __pcpu_type_##size pfo_val__; \
> + asm qual (__pcpu_op2_##size(op, __percpu_arg([var]), "%[val]") \
> + : [val] __pcpu_reg_##size("=", pfo_val__) \
> + : [var] "m" (_var)); \
> + (typeof(_var))(unsigned long) pfo_val__; \
> })
>
> #define percpu_stable_op(op, var) \
> @@ -401,9 +381,9 @@ do { \
> */
> #define this_cpu_read_stable(var) percpu_stable_op("mov", var)
>
> -#define raw_cpu_read_1(pcp) percpu_from_op(, "mov", pcp)
> -#define raw_cpu_read_2(pcp) percpu_from_op(, "mov", pcp)
> -#define raw_cpu_read_4(pcp) percpu_from_op(, "mov", pcp)
> +#define raw_cpu_read_1(pcp) percpu_from_op(1, , "mov", pcp)
> +#define raw_cpu_read_2(pcp) percpu_from_op(2, , "mov", pcp)
> +#define raw_cpu_read_4(pcp) percpu_from_op(4, , "mov", pcp)
>
> #define raw_cpu_write_1(pcp, val) percpu_to_op(1, , "mov", (pcp), val)
> #define raw_cpu_write_2(pcp, val) percpu_to_op(2, , "mov", (pcp), val)
> @@ -433,9 +413,9 @@ do { \
> #define raw_cpu_xchg_2(pcp, val) raw_percpu_xchg_op(pcp, val)
> #define raw_cpu_xchg_4(pcp, val) raw_percpu_xchg_op(pcp, val)
>
> -#define this_cpu_read_1(pcp) percpu_from_op(volatile, "mov", pcp)
> -#define this_cpu_read_2(pcp) percpu_from_op(volatile, "mov", pcp)
> -#define this_cpu_read_4(pcp) percpu_from_op(volatile, "mov", pcp)
> +#define this_cpu_read_1(pcp) percpu_from_op(1, volatile, "mov", pcp)
> +#define this_cpu_read_2(pcp) percpu_from_op(2, volatile, "mov", pcp)
> +#define this_cpu_read_4(pcp) percpu_from_op(4, volatile, "mov", pcp)
> #define this_cpu_write_1(pcp, val) percpu_to_op(1, volatile, "mov", (pcp), val)
> #define this_cpu_write_2(pcp, val) percpu_to_op(2, volatile, "mov", (pcp), val)
> #define this_cpu_write_4(pcp, val) percpu_to_op(4, volatile, "mov", (pcp), val)
> @@ -488,7 +468,7 @@ do { \
> * 32 bit must fall back to generic operations.
> */
> #ifdef CONFIG_X86_64
> -#define raw_cpu_read_8(pcp) percpu_from_op(, "mov", pcp)
> +#define raw_cpu_read_8(pcp) percpu_from_op(8, , "mov", pcp)
> #define raw_cpu_write_8(pcp, val) percpu_to_op(8, , "mov", (pcp), val)
> #define raw_cpu_add_8(pcp, val) percpu_add_op(, (pcp), val)
> #define raw_cpu_and_8(pcp, val) percpu_to_op(8, , "and", (pcp), val)
> @@ -497,7 +477,7 @@ do { \
> #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)
>
> -#define this_cpu_read_8(pcp) percpu_from_op(volatile, "mov", pcp)
> +#define this_cpu_read_8(pcp) percpu_from_op(8, volatile, "mov", pcp)
> #define this_cpu_write_8(pcp, val) percpu_to_op(8, volatile, "mov", (pcp), val)
> #define this_cpu_add_8(pcp, val) percpu_add_op(volatile, (pcp), val)
> #define this_cpu_and_8(pcp, val) percpu_to_op(8, volatile, "and", (pcp), val)
> --
> 2.25.4
>
--
Thanks,
~Nick Desaulniers
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