linux-kernel - Re: [v6 PATCH] RISC-V: Remove unsupported isa string info print

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Date:   Tue, 1 Oct 2019 00:02:36 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Atish Patra <atish.patra@....com>
Cc:     linux-kernel@...r.kernel.org, Albert Ou <aou@...s.berkeley.edu>,
        Anup Patel <anup@...infault.org>,
        Palmer Dabbelt <palmer@...ive.com>,
        Johan Hovold <johan@...nel.org>, hch@...radead.org,
        Paul Walmsley <paul.walmsley@...ive.com>,
        linux-riscv@...ts.infradead.org
Subject: Re: [v6 PATCH] RISC-V: Remove unsupported isa string info print

On Mon, Sep 30, 2019 at 05:23:18PM -0700, Atish Patra wrote:
> /proc/cpuinfo should just print all the isa string as an information
> instead of determining what is supported or not. ELF hwcap can be
> used by the userspace to figure out that.
> 
> Simplify the isa string printing by removing the unsupported isa string
> print and all related code.
> 
> The relevant discussion can be found at
> http://lists.infradead.org/pipermail/linux-riscv/2019-September/006702.html

This looks good, but can you also rename the orig_isa argument to isa
now that we never modify it?

>  	/*
>  	 * Linux doesn't support rv32e or rv128i, and we only support booting
>  	 * kernels on harts with the same ISA that the kernel is compiled for.
>  	 */
>  #if defined(CONFIG_32BIT)
> -	if (strncmp(isa, "rv32i", 5) != 0)
> +	if (strncmp(orig_isa, "rv32i", 5) != 0)
>  		return;
>  #elif defined(CONFIG_64BIT)
> -	if (strncmp(isa, "rv64i", 5) != 0)
> +	if (strncmp(orig_isa, "rv64i", 5) != 0)
>  		return;
>  #endif

And I don't think having these checks here makes much sense.  If we want
to check this at all we should do it somewhere in the boot process.