Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754799AbaGNMhQ (ORCPT ); Mon, 14 Jul 2014 08:37:16 -0400 Received: from mho-02-ewr.mailhop.org ([204.13.248.72]:48027 "EHLO mho-02-ewr.mailhop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754637AbaGNMhK (ORCPT ); Mon, 14 Jul 2014 08:37:10 -0400 X-Mail-Handler: Dyn Standard SMTP by Dyn X-Originating-IP: 96.249.243.124 X-Report-Abuse-To: abuse@dyndns.com (see http://www.dyndns.com/services/sendlabs/outbound_abuse.html for abuse reporting information) X-MHO-User: U2FsdGVkX19m0c3eoYCsJ1YB+Etg13bWTIvtYmJW8+4= X-DKIM: OpenDKIM Filter v2.0.1 titan 4102C5AA9E5 Date: Mon, 14 Jul 2014 08:37:00 -0400 From: Jason Cooper To: Amit Shah Cc: linux-kernel@vger.kernel.org, Virtualization List , Rusty Russell , herbert@gondor.apana.org.au, keescook@chromium.org Subject: Re: [RFC PATCH 1/3] hw_random: allow RNG devices to give early randomness after a delay Message-ID: <20140714123700.GP13108@titan.lakedaemon.net> References: <685be569a29015d3ee56cc3f782d81cae06d52b9.1405277045.git.amit.shah@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <685be569a29015d3ee56cc3f782d81cae06d52b9.1405277045.git.amit.shah@redhat.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 14, 2014 at 10:05:19AM +0530, Amit Shah wrote: > Some RNG devices may not be ready to give early randomness at probe() > time, and hence lose out on the opportunity to contribute to system > randomness at boot- or device hotplug- time. > > This commit schedules a delayed work item for such devices, and fetches > early randomness after a delay. Currently the delay is 500ms, which is > enough for the lone device that needs such treatment: virtio-rng. > > CC: Kees Cook > CC: Jason Cooper > CC: Herbert Xu > Signed-off-by: Amit Shah > --- > drivers/char/hw_random/core.c | 20 +++++++++++++++++++- > include/linux/hw_random.h | 8 ++++++++ > 2 files changed, 27 insertions(+), 1 deletion(-) > > diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c > index c4419ea..2a765fd 100644 > --- a/drivers/char/hw_random/core.c > +++ b/drivers/char/hw_random/core.c > @@ -63,7 +63,7 @@ static size_t rng_buffer_size(void) > return SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES; > } > > -static void add_early_randomness(struct hwrng *rng) > +static void get_early_randomness(struct hwrng *rng) > { > unsigned char bytes[16]; > int bytes_read; > @@ -79,6 +79,21 @@ static void add_early_randomness(struct hwrng *rng) > add_device_randomness(bytes, bytes_read); > } > > +static void sched_init_random(struct work_struct *work) > +{ > + struct hwrng *rng = container_of(work, struct hwrng, dwork.work); > + > + get_early_randomness(rng); > +} > + > +static void add_early_randomness(struct hwrng *rng) The add/get naming seems awkward in the above hunks. > +{ > + if (!(rng->flags & HWRNG_DELAY_READ_AT_INIT)) > + return get_early_randomness(rng); > + > + schedule_delayed_work(&rng->dwork, msecs_to_jiffies(500)); > +} > + Perhaps instead of rng->flags and a hardcoded delay, we could have rng->seed_delay = msecs_to_jiffies(500) in virtio-rng? Then you can just call unconditionally: schedule_delayed_work(&rng->dwork, rng->seed_delay); I think that would be a more extensible solution should other drivers show up with the same issue. thx, Jason. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/