linux-kernel - Re: [PATCH v3 2/3] powerpc/powernv: wire up rng during setup

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Message-ID: <709016db-7bd2-c2ad-76ed-1dfee1c9c5c4@csgroup.eu>
Date:   Sat, 11 Jun 2022 16:25:26 +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 v3 2/3] powerpc/powernv: wire up rng during setup_arch



Le 11/06/2022 à 17:10, 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. 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>

Reviewed-by: Christophe Leroy <christophe.leroy@...roup.eu>

> ---
>   arch/powerpc/platforms/powernv/powernv.h |  2 ++
>   arch/powerpc/platforms/powernv/rng.c     | 18 +++++-------------
>   arch/powerpc/platforms/powernv/setup.c   |  2 ++
>   3 files changed, 9 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/powernv/powernv.h b/arch/powerpc/platforms/powernv/powernv.h
> index e297bf4abfcb..fd3f5e1eb10b 100644
> --- a/arch/powerpc/platforms/powernv/powernv.h
> +++ b/arch/powerpc/platforms/powernv/powernv.h
> @@ -42,4 +42,6 @@ ssize_t memcons_copy(struct memcons *mc, char *to, loff_t pos, size_t count);
>   u32 __init memcons_get_size(struct memcons *mc);
>   struct memcons *__init memcons_init(struct device_node *node, const char *mc_prop_name);
>   
> +void powernv_rng_init(void);
> +
>   #endif /* _POWERNV_H */
> diff --git a/arch/powerpc/platforms/powernv/rng.c b/arch/powerpc/platforms/powernv/rng.c
> index e3d44b36ae98..c86bf097e407 100644
> --- a/arch/powerpc/platforms/powernv/rng.c
> +++ b/arch/powerpc/platforms/powernv/rng.c
> @@ -17,6 +17,7 @@
>   #include <asm/prom.h>
>   #include <asm/machdep.h>
>   #include <asm/smp.h>
> +#include "powernv.h"
>   
>   #define DARN_ERR 0xFFFFFFFFFFFFFFFFul
>   
> @@ -84,24 +85,20 @@ 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 +160,12 @@ 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)
> +void __init powernv_rng_init(void)
>   {
>   	struct device_node *dn;
>   	int rc;
> @@ -188,7 +183,4 @@ 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..a5fcb6796b22 100644
> --- a/arch/powerpc/platforms/powernv/setup.c
> +++ b/arch/powerpc/platforms/powernv/setup.c
> @@ -203,6 +203,8 @@ static void __init pnv_setup_arch(void)
>   	pnv_check_guarded_cores();
>   
>   	/* XXX PMCS */
> +
> +	powernv_rng_init();
>   }
>   
>   static void __init pnv_init(void)