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From:   =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn@kernel.org>
To:     Alexandre Ghiti <alexghiti@rivosinc.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org
Cc:     Alexandre Ghiti <alexghiti@rivosinc.com>
Subject: Re: [PATCH] riscv: Allow to downgrade paging mode from the command
 line
In-Reply-To: <20221214143311.960266-1-alexghiti@rivosinc.com>
References: <20221214143311.960266-1-alexghiti@rivosinc.com>
Date:   Wed, 14 Dec 2022 16:38:57 +0100
Message-ID: <87cz8m3sha.fsf@all.your.base.are.belong.to.us>
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Alexandre Ghiti <alexghiti@rivosinc.com> writes:

> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index b56a0a75533f..8140fefe0e57 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -752,12 +752,35 @@ static void __init disable_pgtable_l4(void)
>   * then read SATP to see if the configuration was taken into account
>   * meaning sv48 is supported.
>   */
> -static __init void set_satp_mode(void)
> +static __init void set_satp_mode(uintptr_t dtb_pa)
>  {
>  	u64 identity_satp, hw_satp;
>  	uintptr_t set_satp_mode_pmd =3D ((unsigned long)set_satp_mode) & PMD_MA=
SK;
>  	bool check_l4 =3D false;
>=20=20
> +#ifndef CONFIG_KASAN
> +	/*
> +	 * The below fdt functions are kasan instrumented, since at this point
> +	 * there is no mapping for the kasan shadow memory, this can't be used
> +	 * when kasan is enabled.
> +	 */
> +	int chosen_node;
> +
> +	chosen_node =3D fdt_path_offset((void *)dtb_pa, "/chosen");
> +	if (chosen_node >=3D 0) {
> +		const char *cmdline =3D fdt_getprop((void *)dtb_pa, chosen_node,
> +						  "bootargs", NULL);

The command line handling needs to honor CONFIG_CMDLINE_FORCE and
CONFIG_CMDLINE_EXTEND (which makes it possible to use no{4,5}lvl *and*
KASAN ;-)).


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