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Date: Thu, 1 Feb 2024 20:55:06 -0800
From: Charlie Jenkins <charlie@rivosinc.com>
To: Elliot Berman <quic_eberman@quicinc.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Jisheng Zhang <jszhang@kernel.org>, Evan Green <evan@rivosinc.com>,
	=?iso-8859-1?Q?Cl=E9ment_L=E9ger?= <cleger@rivosinc.com>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] riscv: Disable misaligned access probe when
 CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
Message-ID: <Zbx1qlcfWJIBLobb@ghost>
References: <20240201-disable_misaligned_probe_config-v2-0-77c368bed7b2@rivosinc.com>
 <20240201-disable_misaligned_probe_config-v2-2-77c368bed7b2@rivosinc.com>
 <gtwet3x2fokbne5642vleyp5u7pqjl2lbtbngjjfavmgvvytzg@z2gx6xoa3hvl>
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On Thu, Feb 01, 2024 at 08:31:10PM -0800, Elliot Berman wrote:
> Hi Charlie,
> 
> On Thu, Feb 01, 2024 at 03:30:46PM -0800, Charlie Jenkins wrote:
> > When CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is selected, the cpus can be
> > set to have fast misaligned access without needing to probe.
> > 
> > Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
> > ---
> >  arch/riscv/Kconfig                               |   1 +
> >  arch/riscv/include/asm/cpufeature.h              |   7 +
> >  arch/riscv/include/asm/misaligned_access_speed.h |  29 +++
> >  arch/riscv/kernel/Makefile                       |   3 +
> >  arch/riscv/kernel/cpufeature.c                   | 255 ----------------------
> >  arch/riscv/kernel/misaligned_access_speed.c      | 265 +++++++++++++++++++++++
> >  arch/riscv/kernel/sys_hwprobe.c                  |   4 +
> >  7 files changed, 309 insertions(+), 255 deletions(-)
> > 
> > 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)
> 
> Should this be CONFIG_RISCV_EFFICIENT_UNALIGNED_ACCESS ?

Oh thank you Elliot! Yes it is. I was going back and forth on whether I
wanted this to be CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS or
CONFIG_RISCV_EFFICIENT_UNALIGNED_ACCESS and I must have mistyped when I
was changing it. I settled on CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
everywhere else so this should also use that instead. These two configs
are effectively the same since the only way to select
CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is by selecting
CONFIG_RISCV_EFFICIENT_UNALIGNED_ACCESS.

- Charlie

> 
> > +obj-y	+= misaligned_access_speed.o
> > +endif
> >  obj-$(CONFIG_FPU)		+= fpu.o
> >  obj-$(CONFIG_RISCV_ISA_V)	+= vector.o
> >  obj-$(CONFIG_RISCV_ISA_V)	+= kernel_mode_vector.o