linux-kernel - Re: [PATCH v2 2/2] riscv: Disable misaligned access probe when CONFIG_HAVE_EFFICIENT_UNALIGNED

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Date: Fri, 2 Feb 2024 15:13:31 -0800
From: Charlie Jenkins <charlie@...osinc.com>
To: Eric Biggers <ebiggers@...nel.org>
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Jisheng Zhang <jszhang@...nel.org>, Evan Green <evan@...osinc.com>,
	Clément Léger <cleger@...osinc.com>,
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] riscv: Disable misaligned access probe when
 CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS

On Fri, Feb 02, 2024 at 03:01:01PM -0800, Eric Biggers wrote:
> On Thu, Feb 01, 2024 at 03:30:46PM -0800, Charlie Jenkins wrote:
> > diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/cpufeature.h
> > index eb3ac304fc42..3a29d8e30e05 100644
> > --- a/arch/riscv/include/asm/cpufeature.h
> > +++ b/arch/riscv/include/asm/cpufeature.h
> > @@ -51,6 +51,7 @@ static inline bool check_unaligned_access_emulated(int cpu)
> >  static inline void unaligned_emulation_finish(void) {}
> >  #endif
> >  
> > +#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
> 
> #ifdef..#else..#endif is more readable than #ifndef..#else..#endif.
> 
> > diff --git a/arch/riscv/include/asm/misaligned_access_speed.h b/arch/riscv/include/asm/misaligned_access_speed.h
> > new file mode 100644
> > index 000000000000..81df2aa6fa6b
> > --- /dev/null
> > +++ b/arch/riscv/include/asm/misaligned_access_speed.h
> 
> This new header file isn't included from anywhere.
> 

I thought I deleted that...

> > diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
> > index f71910718053..8be7f17da9ab 100644
> > --- a/arch/riscv/kernel/Makefile
> > +++ b/arch/riscv/kernel/Makefile
> > @@ -62,6 +62,9 @@ obj-y	+= tests/
> >  obj-$(CONFIG_MMU) += vdso.o vdso/
> >  
> >  obj-$(CONFIG_RISCV_MISALIGNED)	+= traps_misaligned.o
> > +ifneq ($(RISCV_EFFICIENT_UNALIGNED_ACCESS), y)
> > +obj-y	+= misaligned_access_speed.o
> > +endif
> 
> CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
> 
> > diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
> > index a7c56b41efd2..3f1a6edfdb08 100644
> > --- a/arch/riscv/kernel/sys_hwprobe.c
> > +++ b/arch/riscv/kernel/sys_hwprobe.c
> > @@ -149,6 +149,7 @@ static bool hwprobe_ext0_has(const struct cpumask *cpus, unsigned long ext)
> >  
> >  static u64 hwprobe_misaligned(const struct cpumask *cpus)
> >  {
> > +#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
> >  	int cpu;
> >  	u64 perf = -1ULL;
> >  
> > @@ -168,6 +169,9 @@ static u64 hwprobe_misaligned(const struct cpumask *cpus)
> >  		return RISCV_HWPROBE_MISALIGNED_UNKNOWN;
> >  
> >  	return perf;
> > +#else
> > +	return RISCV_HWPROBE_MISALIGNED_FAST;
> > +#endif
> 
> #ifdef..#else..#endif is more readable than #ifndef..#else..#endif.
> 
> - Eric

Thanks for pointing these out, I will send a v3.

- Charlie