linux-kernel - Re: [PATCH] powerpc: clean up UPD

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Message-ID: <c2ebc59f-c14e-d78f-78f0-2204d09cf81c@kernel.org>
Date:   Tue, 14 Sep 2021 09:38:53 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Segher Boessenkool <segher@...nel.crashing.org>,
        David Hildenbrand <david@...hat.com>,
        Michal Hocko <mhocko@...e.com>, Daniel Axtens <dja@...ens.net>,
        Dan Williams <dan.j.williams@...el.com>,
        "Christopher M. Riedl" <cmr@...efail.de>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        kvm-ppc@...r.kernel.org
Subject: Re: [PATCH] powerpc: clean up UPD_CONSTR

On 9/14/2021 9:17 AM, Nick Desaulniers wrote:
> UPD_CONSTR was previously a preprocessor define for an old GCC 4.9 inline
> asm bug with m<> constraints.
> 
> Fixes: 6563139d90ad ("powerpc: remove GCC version check for UPD_CONSTR")
> Suggested-by: Nathan Chancellor <nathan@...nel.org>
> Suggested-by: Christophe Leroy <christophe.leroy@...roup.eu>
> Suggested-by: Michael Ellerman <mpe@...erman.id.au>
> Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>

Reviewed-by: Nathan Chancellor <nathan@...nel.org>

> ---
>   arch/powerpc/include/asm/asm-const.h | 2 --
>   arch/powerpc/include/asm/atomic.h    | 8 ++++----
>   arch/powerpc/include/asm/io.h        | 4 ++--
>   arch/powerpc/include/asm/uaccess.h   | 6 +++---
>   arch/powerpc/kvm/powerpc.c           | 4 ++--
>   5 files changed, 11 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/asm-const.h b/arch/powerpc/include/asm/asm-const.h
> index dbfa5e1e3198..bfb3c3534877 100644
> --- a/arch/powerpc/include/asm/asm-const.h
> +++ b/arch/powerpc/include/asm/asm-const.h
> @@ -12,6 +12,4 @@
>   #  define ASM_CONST(x)		__ASM_CONST(x)
>   #endif
>   
> -#define UPD_CONSTR "<>"
> -
>   #endif /* _ASM_POWERPC_ASM_CONST_H */
> diff --git a/arch/powerpc/include/asm/atomic.h b/arch/powerpc/include/asm/atomic.h
> index 6a53ef178bfd..fd594fdbd84d 100644
> --- a/arch/powerpc/include/asm/atomic.h
> +++ b/arch/powerpc/include/asm/atomic.h
> @@ -27,14 +27,14 @@ static __inline__ int arch_atomic_read(const atomic_t *v)
>   {
>   	int t;
>   
> -	__asm__ __volatile__("lwz%U1%X1 %0,%1" : "=r"(t) : "m"UPD_CONSTR(v->counter));
> +	__asm__ __volatile__("lwz%U1%X1 %0,%1" : "=r"(t) : "m<>"(v->counter));
>   
>   	return t;
>   }
>   
>   static __inline__ void arch_atomic_set(atomic_t *v, int i)
>   {
> -	__asm__ __volatile__("stw%U0%X0 %1,%0" : "=m"UPD_CONSTR(v->counter) : "r"(i));
> +	__asm__ __volatile__("stw%U0%X0 %1,%0" : "=m<>"(v->counter) : "r"(i));
>   }
>   
>   #define ATOMIC_OP(op, asm_op)						\
> @@ -320,14 +320,14 @@ static __inline__ s64 arch_atomic64_read(const atomic64_t *v)
>   {
>   	s64 t;
>   
> -	__asm__ __volatile__("ld%U1%X1 %0,%1" : "=r"(t) : "m"UPD_CONSTR(v->counter));
> +	__asm__ __volatile__("ld%U1%X1 %0,%1" : "=r"(t) : "m<>"(v->counter));
>   
>   	return t;
>   }
>   
>   static __inline__ void arch_atomic64_set(atomic64_t *v, s64 i)
>   {
> -	__asm__ __volatile__("std%U0%X0 %1,%0" : "=m"UPD_CONSTR(v->counter) : "r"(i));
> +	__asm__ __volatile__("std%U0%X0 %1,%0" : "=m<>"(v->counter) : "r"(i));
>   }
>   
>   #define ATOMIC64_OP(op, asm_op)						\
> diff --git a/arch/powerpc/include/asm/io.h b/arch/powerpc/include/asm/io.h
> index f130783c8301..beba4979bff9 100644
> --- a/arch/powerpc/include/asm/io.h
> +++ b/arch/powerpc/include/asm/io.h
> @@ -122,7 +122,7 @@ static inline u##size name(const volatile u##size __iomem *addr)	\
>   {									\
>   	u##size ret;							\
>   	__asm__ __volatile__("sync;"#insn"%U1%X1 %0,%1;twi 0,%0,0;isync"\
> -		: "=r" (ret) : "m"UPD_CONSTR (*addr) : "memory");	\
> +		: "=r" (ret) : "m<>" (*addr) : "memory");	\
>   	return ret;							\
>   }
>   
> @@ -130,7 +130,7 @@ static inline u##size name(const volatile u##size __iomem *addr)	\
>   static inline void name(volatile u##size __iomem *addr, u##size val)	\
>   {									\
>   	__asm__ __volatile__("sync;"#insn"%U0%X0 %1,%0"			\
> -		: "=m"UPD_CONSTR (*addr) : "r" (val) : "memory");	\
> +		: "=m<>" (*addr) : "r" (val) : "memory");	\
>   	mmiowb_set_pending();						\
>   }
>   
> diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
> index 22c79ab40006..63316100080c 100644
> --- a/arch/powerpc/include/asm/uaccess.h
> +++ b/arch/powerpc/include/asm/uaccess.h
> @@ -86,7 +86,7 @@ __pu_failed:							\
>   		"1:	" op "%U1%X1 %0,%1	# put_user\n"	\
>   		EX_TABLE(1b, %l2)				\
>   		:						\
> -		: "r" (x), "m"UPD_CONSTR (*addr)		\
> +		: "r" (x), "m<>" (*addr)		\
>   		:						\
>   		: label)
>   
> @@ -143,7 +143,7 @@ do {								\
>   		"1:	"op"%U1%X1 %0, %1	# get_user\n"	\
>   		EX_TABLE(1b, %l2)				\
>   		: "=r" (x)					\
> -		: "m"UPD_CONSTR (*addr)				\
> +		: "m<>" (*addr)				\
>   		:						\
>   		: label)
>   
> @@ -200,7 +200,7 @@ __gus_failed:								\
>   		".previous\n"				\
>   		EX_TABLE(1b, 3b)			\
>   		: "=r" (err), "=r" (x)			\
> -		: "m"UPD_CONSTR (*addr), "i" (-EFAULT), "0" (err))
> +		: "m<>" (*addr), "i" (-EFAULT), "0" (err))
>   
>   #ifdef __powerpc64__
>   #define __get_user_asm2(x, addr, err)			\
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index b4e6f70b97b9..3fd037d36afb 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -1094,7 +1094,7 @@ static inline u64 sp_to_dp(u32 fprs)
>   
>   	preempt_disable();
>   	enable_kernel_fp();
> -	asm ("lfs%U1%X1 0,%1; stfd%U0%X0 0,%0" : "=m"UPD_CONSTR (fprd) : "m"UPD_CONSTR (fprs)
> +	asm ("lfs%U1%X1 0,%1; stfd%U0%X0 0,%0" : "=m<>" (fprd) : "m<>" (fprs)
>   	     : "fr0");
>   	preempt_enable();
>   	return fprd;
> @@ -1106,7 +1106,7 @@ static inline u32 dp_to_sp(u64 fprd)
>   
>   	preempt_disable();
>   	enable_kernel_fp();
> -	asm ("lfd%U1%X1 0,%1; stfs%U0%X0 0,%0" : "=m"UPD_CONSTR (fprs) : "m"UPD_CONSTR (fprd)
> +	asm ("lfd%U1%X1 0,%1; stfs%U0%X0 0,%0" : "=m<>" (fprs) : "m<>" (fprd)
>   	     : "fr0");
>   	preempt_enable();
>   	return fprs;
>