linux-kernel - Re: [PATCH v1] RISC-V: clarify what some RISCV

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Date: Fri, 19 Apr 2024 12:06:59 +0100
From: Conor Dooley <conor@...nel.org>
To: Andrew Jones <ajones@...tanamicro.com>
Cc: linux-riscv@...ts.infradead.org,
	Conor Dooley <conor.dooley@...rochip.com>,
	Björn Töpel <bjorn@...osinc.com>,
	Samuel Holland <samuel.holland@...ive.com>,
	Pu Lehui <pulehui@...weicloud.com>,
	Björn Töpel <bjorn@...nel.org>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] RISC-V: clarify what some RISCV_ISA* config options do

On Fri, Apr 19, 2024 at 01:01:52PM +0200, Andrew Jones wrote:
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index 6d64888134ba..c3a7793b0a7c 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -503,8 +503,8 @@ config RISCV_ISA_SVNAPOT
> >  	depends on RISCV_ALTERNATIVE
> >  	default y
> >  	help
> > -	  Allow kernel to detect the Svnapot ISA-extension dynamically at boot
> > -	  time and enable its usage.
> > +	  Add support for the Svnapot ISA-extension when it is detected by
> > +	  the kernel at boot.
> 
> I'm not sure we need the 'by the kernel', since I guess that's implied by
> being in a Kconfig help text, but either way is fine by me.

I think we do, given some of the options are required for userspace to
use it and others are not. Distinguishing between them doesn't cos us
more than a few characters so I think it is worthwhile.


> > @@ -686,7 +687,8 @@ config FPU
> >  	default y
> >  	help
> >  	  Say N here if you want to disable all floating-point related procedure
> > -	  in the kernel.
> > +	  in the kernel. Without this option enabled, neither the kernel nor
> > +	  userspace may use floating-point procedures.
> >  
> >  	  If you don't know what to do here, say Y.
> >
> 
> Zicboz could also use some clarification, right? Or is the fact that
> RISCV_ISA_ZICBOZ enables the use in both the kernel and userspace the
> reason "Enable the use of the Zicboz extension (cbo.zero instruction)
> when available." looks sufficient? Maybe Zicboz should follow the
> "Say N here if..." pattern of V and FPU?

Yeah, I think I just overlooked Zicboz. If the kernel option is needed
for userspace to use it then yeah, it should follow the same wording as
V/FPU.

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