linux-kernel - Re: [PATCH v2 2/3] powerpc/powernv: wire up rng during setup

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Message-ID: <d310a8cf-79f8-89ed-41fd-ebe0281a67f4@csgroup.eu>
Date:   Sat, 11 Jun 2022 14:42:43 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     "Jason A. Donenfeld" <Jason@...c4.com>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Michael Ellerman <mpe@...erman.id.au>
CC:     "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] powerpc/powernv: wire up rng during setup_arch



Le 11/06/2022 à 12:04, Jason A. Donenfeld a écrit :
> The platform's RNG must be available before random_init() in order to be
> useful for initial seeding, which in turn means that it needs to be
> called from setup_arch(), rather than from an init call. Fortunately,
> each platform already has a setup_arch function pointer, which means
> it's easy to wire this up for each of the three platforms that have an
> RNG. This commit also removes some noisy log messages that don't add
> much.
> 
> Cc: stable@...r.kernel.org
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Christophe Leroy <christophe.leroy@...roup.eu>
> Fixes: a4da0d50b2a0 ("powerpc: Implement arch_get_random_long/int() for powernv")
> Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
> ---
>   arch/powerpc/platforms/powernv/rng.c   | 17 ++++-------------
>   arch/powerpc/platforms/powernv/setup.c |  4 ++++
>   2 files changed, 8 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/powernv/rng.c b/arch/powerpc/platforms/powernv/rng.c
> index e3d44b36ae98..ef24e72a1b69 100644
> --- a/arch/powerpc/platforms/powernv/rng.c
> +++ b/arch/powerpc/platforms/powernv/rng.c
> @@ -84,24 +84,20 @@ static int powernv_get_random_darn(unsigned long *v)
>   	return 1;
>   }
>   
> -static int __init initialise_darn(void)
> +static void __init initialise_darn(void)
>   {
>   	unsigned long val;
>   	int i;
>   
>   	if (!cpu_has_feature(CPU_FTR_ARCH_300))
> -		return -ENODEV;
> +		return;
>   
>   	for (i = 0; i < 10; i++) {
>   		if (powernv_get_random_darn(&val)) {
>   			ppc_md.get_random_seed = powernv_get_random_darn;
> -			return 0;
> +			return;
>   		}
>   	}
> -
> -	pr_warn("Unable to use DARN for get_random_seed()\n");
> -
> -	return -EIO;
>   }
>   
>   int powernv_get_random_long(unsigned long *v)
> @@ -163,14 +159,12 @@ static __init int rng_create(struct device_node *dn)
>   
>   	rng_init_per_cpu(rng, dn);
>   
> -	pr_info_once("Registering arch random hook.\n");
> -
>   	ppc_md.get_random_seed = powernv_get_random_long;
>   
>   	return 0;
>   }
>   
> -static __init int rng_init(void)
> +__init void powernv_rng_init(void)
>   {
>   	struct device_node *dn;
>   	int rc;
> @@ -188,7 +182,4 @@ static __init int rng_init(void)
>   	}
>   
>   	initialise_darn();
> -
> -	return 0;
>   }
> -machine_subsys_initcall(powernv, rng_init);
> diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
> index 824c3ad7a0fa..a0c5217bc5c0 100644
> --- a/arch/powerpc/platforms/powernv/setup.c
> +++ b/arch/powerpc/platforms/powernv/setup.c
> @@ -184,6 +184,8 @@ static void __init pnv_check_guarded_cores(void)
>   	}
>   }
>   
> +__init void powernv_rng_init(void);
> +

Same here, the prototype should go in a header file., should be 'void 
__init' (and indeed the __init is pointless in the prototype, only 
matters in the function definition).

Maybe the name should be pnv_rng_init() like the setup arch below.

>   static void __init pnv_setup_arch(void)
>   {
>   	set_arch_panic_timeout(10, ARCH_PANIC_TIMEOUT);
> @@ -203,6 +205,8 @@ static void __init pnv_setup_arch(void)
>   	pnv_check_guarded_cores();
>   
>   	/* XXX PMCS */
> +
> +	powernv_rng_init();
>   }
>   
>   static void __init pnv_init(void)