linux-kernel - Re: [PATCH v4 15/21] arm64: Add an aliasing facility for the idreg override

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Date:   Mon, 18 Jan 2021 13:18:39 +0000
From:   David Brazdil <dbrazdil@...gle.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Jing Zhang <jingzhangos@...gle.com>,
        Ajay Patil <pajay@....qualcomm.com>,
        Prasad Sodagudi <psodagud@...eaurora.org>,
        Srinivas Ramana <sramana@...eaurora.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        kernel-team@...roid.com
Subject: Re: [PATCH v4 15/21] arm64: Add an aliasing facility for the idreg
 override

On Mon, Jan 18, 2021 at 09:45:27AM +0000, Marc Zyngier wrote:
> In order to map the override of idregs to options that a user
> can easily understand, let's introduce yet another option
> array, which maps an option to the corresponding idreg options.
> 
> Signed-off-by: Marc Zyngier <maz@...nel.org>
Acked-by: David Brazdil <dbrazdil@...gle.com>

> ---
>  arch/arm64/kernel/idreg-override.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
> index 75d9845f489b..16bc8b3b93ae 100644
> --- a/arch/arm64/kernel/idreg-override.c
> +++ b/arch/arm64/kernel/idreg-override.c
> @@ -37,6 +37,12 @@ static const struct reg_desc * const regs[] __initdata = {
>  	&mmfr1,
>  };
>  
> +static const struct {
> +	const char * const	alias;
> +	const char * const	feature;
> +} aliases[] __initdata = {
> +};
> +
>  static int __init find_field(const char *cmdline, const struct reg_desc *reg,
>  			     int f, u64 *v)
>  {
> @@ -80,6 +86,18 @@ static void __init match_options(const char *cmdline)
>  	}
>  }
>  
> +static __init void match_aliases(const char *cmdline)
> +{
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(aliases); i++) {
> +		char *str = strstr(cmdline, aliases[i].alias);
> +
> +		if ((str == cmdline || (str > cmdline && *(str - 1) == ' ')))

nit: Extract to a 'cmdline_contains' helper? Took me a good few seconds to
parse this in the previous patch. Giving it a name would help, and now it's
also shared.

> +			match_options(aliases[i].feature);
> +	}
> +}
> +
>  static __init void parse_cmdline(void)
>  {
>  	if (!IS_ENABLED(CONFIG_CMDLINE_FORCE)) {
> @@ -100,6 +118,7 @@ static __init void parse_cmdline(void)
>  			goto out;
>  
>  		match_options(prop);
> +		match_aliases(prop);
>  
>  		if (!IS_ENABLED(CONFIG_CMDLINE_EXTEND))
>  			return;
> @@ -107,6 +126,7 @@ static __init void parse_cmdline(void)
>  
>  out:
>  	match_options(CONFIG_CMDLINE);
> +	match_aliases(CONFIG_CMDLINE);
>  }
>  
>  void __init init_shadow_regs(void)
> -- 
> 2.29.2
>