linux-kernel - Re: [PATCH] s390/zcrypt: enable s390 hwrng to seed kernel entropy

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Date:	Mon, 11 Aug 2014 15:56:11 +0200
From:	Torsten Duwe <duwe@....de>
To:	Ingo Tuchscherer <ingo.tuchscherer@...ibm.com>
Cc:	linux-kernel@...r.kernel.org, Theodore Ts'o <tytso@....edu>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Gerald Schaefer <gerald.schaefer@...ibm.com>,
	Heiko Carstens <heicars2@...ux.vnet.ibm.com>,
	Hendrik Brueckner <brueckner@...ibm.com>,
	Matt Mackall <mpm@...enic.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Harald Freudenberger <freude@...ibm.com>,
	Ingo Tuchscherer <ingo.tuchscherer@...ux.vnet.ibm.com>
Subject: Re: [PATCH] s390/zcrypt: enable s390 hwrng to seed kernel entropy

On Wed, Jul 30, 2014 at 02:17:36PM +0200, Ingo Tuchscherer wrote:
> Set the 'quality' property in the zcrypt rng device structure to enable the
> zcrypt hwrng device to take part in the kernel entropy seeding process.
> A module parameter named hwrng_seed will be introduced to disable the
> participation. By default this parameter is set to 1 (enabled).

I only had a one-liner that simply enabled it. I guess the extra switch
is for certification scenarios? Anyway,

Acked-by: Torsten Duwe <duwe@...e.de>
> 
> Signed-off-by: Ingo Tuchscherer <ingo.tuchscherer@...ibm.com>
> ---
>  drivers/s390/crypto/ap_bus.c     | 5 +++++
>  drivers/s390/crypto/ap_bus.h     | 1 +
>  drivers/s390/crypto/zcrypt_api.c | 3 +++
>  3 files changed, 9 insertions(+)
> 
> diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c
> index 4038437..19fac5f 100644
> --- a/drivers/s390/crypto/ap_bus.c
> +++ b/drivers/s390/crypto/ap_bus.c
> @@ -85,6 +85,11 @@ static int ap_thread_flag = 0;
>  module_param_named(poll_thread, ap_thread_flag, int, S_IRUSR|S_IRGRP);
>  MODULE_PARM_DESC(poll_thread, "Turn on/off poll thread, default is 0 (off).");
>  
> +int ap_hwrng_seed = 1;
> +EXPORT_SYMBOL(ap_hwrng_seed);
> +module_param_named(hwrng_seed, ap_hwrng_seed, int, S_IRUSR|S_IRGRP);
> +MODULE_PARM_DESC(hwrng_seed, "Turn on/off hwrng auto seed, default is 1 (on).");
> +
>  static struct device *ap_root_device = NULL;
>  static struct ap_config_info *ap_configuration;
>  static DEFINE_SPINLOCK(ap_device_list_lock);
> diff --git a/drivers/s390/crypto/ap_bus.h b/drivers/s390/crypto/ap_bus.h
> index 6405ae2..b0be09a 100644
> --- a/drivers/s390/crypto/ap_bus.h
> +++ b/drivers/s390/crypto/ap_bus.h
> @@ -38,6 +38,7 @@
>  #define AP_POLL_TIME 1		/* Time in ticks between receive polls. */
>  
>  extern int ap_domain_index;
> +extern int ap_hwrng_seed;
>  
>  /**
>   * The ap_qid_t identifier of an ap queue. It contains a
> diff --git a/drivers/s390/crypto/zcrypt_api.c b/drivers/s390/crypto/zcrypt_api.c
> index 0e18c5d..ed91665 100644
> --- a/drivers/s390/crypto/zcrypt_api.c
> +++ b/drivers/s390/crypto/zcrypt_api.c
> @@ -1374,6 +1374,7 @@ static int zcrypt_rng_data_read(struct hwrng *rng, u32 *data)
>  static struct hwrng zcrypt_rng_dev = {
>  	.name		= "zcrypt",
>  	.data_read	= zcrypt_rng_data_read,
> +	.quality	= 990,
>  };
>  
>  static int zcrypt_rng_device_add(void)
> @@ -1388,6 +1389,8 @@ static int zcrypt_rng_device_add(void)
>  			goto out;
>  		}
>  		zcrypt_rng_buffer_index = 0;
> +		if (!ap_hwrng_seed)
> +			zcrypt_rng_dev.quality = 0;
>  		rc = hwrng_register(&zcrypt_rng_dev);
>  		if (rc)
>  			goto out_free;
> -- 
> 1.8.5.5
> 
> --
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