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Message-ID: <CAKwvOdnCcpS_9A2y9tMqeiAg2NfcVx=gNeA2V=+zHknit7wGkg@mail.gmail.com>
Date: Mon, 18 May 2020 14:15:44 -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 2/7] x86/percpu: Clean up percpu_to_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>
> ---
> arch/x86/include/asm/percpu.h | 90 ++++++++++++++---------------------
> 1 file changed, 35 insertions(+), 55 deletions(-)
>
> diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
> index 89f918a3e99b..233c7a78d1a6 100644
> --- a/arch/x86/include/asm/percpu.h
> +++ b/arch/x86/include/asm/percpu.h
> @@ -117,37 +117,17 @@ extern void __bad_percpu_size(void);
> #define __pcpu_reg_imm_4(x) "ri" (x)
> #define __pcpu_reg_imm_8(x) "re" (x)
>
> -#define percpu_to_op(qual, op, var, val) \
> -do { \
> - typedef typeof(var) pto_T__; \
> - if (0) { \
> - pto_T__ pto_tmp__; \
> - pto_tmp__ = (val); \
> - (void)pto_tmp__; \
> - } \
> - switch (sizeof(var)) { \
> - case 1: \
> - asm qual (op "b %1,"__percpu_arg(0) \
> - : "+m" (var) \
> - : "qi" ((pto_T__)(val))); \
> - break; \
> - case 2: \
> - asm qual (op "w %1,"__percpu_arg(0) \
> - : "+m" (var) \
> - : "ri" ((pto_T__)(val))); \
> - break; \
> - case 4: \
> - asm qual (op "l %1,"__percpu_arg(0) \
> - : "+m" (var) \
> - : "ri" ((pto_T__)(val))); \
> - break; \
> - case 8: \
> - asm qual (op "q %1,"__percpu_arg(0) \
> - : "+m" (var) \
> - : "re" ((pto_T__)(val))); \
> - break; \
> - default: __bad_percpu_size(); \
> - } \
> +#define percpu_to_op(size, qual, op, _var, _val) \
> +do { \
> + __pcpu_type_##size pto_val__ = __pcpu_cast_##size(_val); \
> + if (0) { \
> + typeof(_var) pto_tmp__; \
> + pto_tmp__ = (_val); \
> + (void)pto_tmp__; \
> + } \
Please replace the whole `if (0)` block with:
```c
__same_type(_var, _val);
```
from include/linux/compiler.h.
> + asm qual(__pcpu_op2_##size(op, "%[val]", __percpu_arg([var])) \
> + : [var] "+m" (_var) \
> + : [val] __pcpu_reg_imm_##size(pto_val__)); \
> } while (0)
>
> /*
> @@ -425,18 +405,18 @@ do { \
> #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_write_1(pcp, val) percpu_to_op(, "mov", (pcp), val)
> -#define raw_cpu_write_2(pcp, val) percpu_to_op(, "mov", (pcp), val)
> -#define raw_cpu_write_4(pcp, val) percpu_to_op(, "mov", (pcp), val)
> +#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)
> +#define raw_cpu_write_4(pcp, val) percpu_to_op(4, , "mov", (pcp), val)
> #define raw_cpu_add_1(pcp, val) percpu_add_op(, (pcp), val)
> #define raw_cpu_add_2(pcp, val) percpu_add_op(, (pcp), val)
> #define raw_cpu_add_4(pcp, val) percpu_add_op(, (pcp), val)
> -#define raw_cpu_and_1(pcp, val) percpu_to_op(, "and", (pcp), val)
> -#define raw_cpu_and_2(pcp, val) percpu_to_op(, "and", (pcp), val)
> -#define raw_cpu_and_4(pcp, val) percpu_to_op(, "and", (pcp), val)
> -#define raw_cpu_or_1(pcp, val) percpu_to_op(, "or", (pcp), val)
> -#define raw_cpu_or_2(pcp, val) percpu_to_op(, "or", (pcp), val)
> -#define raw_cpu_or_4(pcp, val) percpu_to_op(, "or", (pcp), val)
> +#define raw_cpu_and_1(pcp, val) percpu_to_op(1, , "and", (pcp), val)
> +#define raw_cpu_and_2(pcp, val) percpu_to_op(2, , "and", (pcp), val)
> +#define raw_cpu_and_4(pcp, val) percpu_to_op(4, , "and", (pcp), val)
> +#define raw_cpu_or_1(pcp, val) percpu_to_op(1, , "or", (pcp), val)
> +#define raw_cpu_or_2(pcp, val) percpu_to_op(2, , "or", (pcp), val)
> +#define raw_cpu_or_4(pcp, val) percpu_to_op(4, , "or", (pcp), val)
>
> /*
> * raw_cpu_xchg() can use a load-store since it is not required to be
> @@ -456,18 +436,18 @@ do { \
> #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_write_1(pcp, val) percpu_to_op(volatile, "mov", (pcp), val)
> -#define this_cpu_write_2(pcp, val) percpu_to_op(volatile, "mov", (pcp), val)
> -#define this_cpu_write_4(pcp, val) percpu_to_op(volatile, "mov", (pcp), val)
> +#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)
> #define this_cpu_add_1(pcp, val) percpu_add_op(volatile, (pcp), val)
> #define this_cpu_add_2(pcp, val) percpu_add_op(volatile, (pcp), val)
> #define this_cpu_add_4(pcp, val) percpu_add_op(volatile, (pcp), val)
> -#define this_cpu_and_1(pcp, val) percpu_to_op(volatile, "and", (pcp), val)
> -#define this_cpu_and_2(pcp, val) percpu_to_op(volatile, "and", (pcp), val)
> -#define this_cpu_and_4(pcp, val) percpu_to_op(volatile, "and", (pcp), val)
> -#define this_cpu_or_1(pcp, val) percpu_to_op(volatile, "or", (pcp), val)
> -#define this_cpu_or_2(pcp, val) percpu_to_op(volatile, "or", (pcp), val)
> -#define this_cpu_or_4(pcp, val) percpu_to_op(volatile, "or", (pcp), val)
> +#define this_cpu_and_1(pcp, val) percpu_to_op(1, volatile, "and", (pcp), val)
> +#define this_cpu_and_2(pcp, val) percpu_to_op(2, volatile, "and", (pcp), val)
> +#define this_cpu_and_4(pcp, val) percpu_to_op(4, volatile, "and", (pcp), val)
> +#define this_cpu_or_1(pcp, val) percpu_to_op(1, volatile, "or", (pcp), val)
> +#define this_cpu_or_2(pcp, val) percpu_to_op(2, volatile, "or", (pcp), val)
> +#define this_cpu_or_4(pcp, val) percpu_to_op(4, volatile, "or", (pcp), val)
> #define this_cpu_xchg_1(pcp, nval) percpu_xchg_op(volatile, pcp, nval)
> #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)
> @@ -509,19 +489,19 @@ do { \
> */
> #ifdef CONFIG_X86_64
> #define raw_cpu_read_8(pcp) percpu_from_op(, "mov", pcp)
> -#define raw_cpu_write_8(pcp, val) percpu_to_op(, "mov", (pcp), val)
> +#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(, "and", (pcp), val)
> -#define raw_cpu_or_8(pcp, val) percpu_to_op(, "or", (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_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_write_8(pcp, val) percpu_to_op(volatile, "mov", (pcp), val)
> +#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(volatile, "and", (pcp), val)
> -#define this_cpu_or_8(pcp, val) percpu_to_op(volatile, "or", (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_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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