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Date:   Tue, 8 Oct 2019 08:44:08 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Atish Patra <atish.patra@wdc.com>
Cc:     linux-kernel@vger.kernel.org, Albert Ou <aou@eecs.berkeley.edu>,
        Richard Fontana <rfontana@redhat.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Palmer Dabbelt <palmer@sifive.com>,
        Johan Hovold <johan@kernel.org>,
        Alexandre Ghiti <aghiti@upmem.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Anup Patel <anup@brainfault.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-riscv@lists.infradead.org
Subject: Re: [v1 PATCH  2/2] RISC-V: Consolidate isa correctness check
Message-ID: <20191008154408.GC20318@infradead.org>
References: <20191004012000.2661-1-atish.patra@wdc.com>
 <20191004012000.2661-3-atish.patra@wdc.com>
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> +int riscv_read_check_isa(struct device_node *node, const char **isa)
> +{
> +	u32 hart;
> +
> +	if (of_property_read_u32(node, "reg", &hart)) {
> +		pr_warn("Found CPU without hart ID\n");
> +		return -ENODEV;
> +	}
> +
> +	if (of_property_read_string(node, "riscv,isa", isa)) {
> +		pr_warn("CPU with hartid=%d has no \"riscv,isa\" property\n",
> +			hart);
> +		return -ENODEV;
> +	}
> +
> +	/*
> +	 * 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)
> +		return -ENODEV;
> +#elif defined(CONFIG_64BIT)
> +	if (strncmp(*isa, "rv64i", 5) != 0)
> +		return -ENODEV;
> +#endif

Using IS_ENABLED here would clean the checks up a bit.

> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index b1ade9a49347..eaad5aa07403 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -38,10 +38,8 @@ void riscv_fill_hwcap(void)
>  		if (riscv_of_processor_hartid(node) < 0)
>  			continue;
>  
> -		if (of_property_read_string(node, "riscv,isa", &isa)) {
> -			pr_warn("Unable to find \"riscv,isa\" devicetree entry\n");
> +		if (riscv_read_check_isa(node, &isa) < 0)
>  			continue;

Do we really get rid of warnings if we didn't find anything proper?