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From: "Stephan Müller" <smueller@chronox.de>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-crypto@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
	linux-api@vger.kernel.org,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	"Alexander E. Patrakov" <patrakov@gmail.com>,
	"Ahmed S. Darwish" <darwish.07@gmail.com>,
	"Theodore Y. Ts'o" <tytso@mit.edu>, Willy Tarreau <w@1wt.eu>,
	Matthew Garrett <mjg59@srcf.ucam.org>,
	Vito Caputo <vcaputo@pengaru.com>,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	Jan Kara <jack@suse.cz>, Ray Strode <rstrode@redhat.com>,
	William Jon McCann <mccann@jhu.edu>,
	zhangjs <zachary@baishancloud.com>,
	Andy Lutomirski <luto@kernel.org>,
	Florian Weimer <fweimer@redhat.com>,
	Lennart Poettering <mzxreary@0pointer.de>,
	Nicolai Stange <nstange@suse.de>,
	"Peter, Matthias" <matthias.peter@bsi.bund.de>,
	Marcelo Henrique Cerri <marcelo.cerri@canonical.com>,
	Roman Drahtmueller <draht@schaltsekun.de>,
	Neil Horman <nhorman@redhat.com>
Subject: Re: [PATCH v25 01/12] Linux Random Number Generator
Date: Sun, 17 Nov 2019 11:30:13 +0100
Message-ID: <9486573.CV9Qe9s7RZ@positron.chronox.de> (raw)
In-Reply-To: <alpine.DEB.2.21.1911161216540.14348@nanos.tec.linutronix.de>

Am Samstag, 16. November 2019, 12:25:21 CET schrieb Thomas Gleixner:

Hi Thomas,

> On Sat, 16 Nov 2019, Stephan Müller wrote:
> > +/**
> > + * Hot code path - Callback for interrupt handler
> > + */
> > +void add_interrupt_randomness(int irq, int irq_flags)
> > +{
> > +	lrng_time_process();
> > +
> > +	if (!lrng_pool_highres_timer()) {
> > +		struct pt_regs *regs = get_irq_regs();
> > +		static atomic_t reg_idx = ATOMIC_INIT(0);
> > +		u64 ip;
> > +
> > +		lrng_pool_lfsr_u32(jiffies);
> > +		lrng_pool_lfsr_u32(irq);
> > +		lrng_pool_lfsr_u32(irq_flags);
> > +
> > +		if (regs) {
> > +			u32 *ptr = (u32 *)regs;
> > +			int reg_ptr = atomic_add_return_relaxed(1, &reg_idx);
> > +			size_t n = (sizeof(struct pt_regs) / sizeof(u32));
> > +
> > +			ip = instruction_pointer(regs);
> > +			lrng_pool_lfsr_u32(*(ptr + (reg_ptr % n)));
> > +		} else
> > +			ip = _RET_IP_;
> > +
> > +		lrng_pool_lfsr_u32(ip >> 32);
> > +		lrng_pool_lfsr_u32(ip);
> > +	}
> 
> Is there a way to avoid all that processing right in the interrupt hot
> path and just store the raw data for later processing?

The main code path is lrng_time_process(). This code is streamlined as you 
already suggested: it is very lightweight to the interrupt handler. Compared 
to the existing /dev/random implementation it is about 50% faster.

When measuring the lrng_time_process, it takes on one particular test system 
on average about 65 cycles where on that very same system the 
add_interrupt_randomness code path from the existing /dev/random takes on 
average about 97 cycles.

The additional code you see in the add_interrupt_randomness is only executed 
if lrng_pool_highres_timer is not set. This is not set if the LRNG does not 
find a high-resolution time stamp, i.e. random_get_entropy() returns 0. As on 
most architectures this is now set, this code path is not executed.

This additional code path serves as an emergency code to collect some data 
that smells random and having entropy but not having really much.

It may be a bit more stremlined but since it is hardly used, I left it as it 
is so far. Do you see the need to streamline it more at this time?

Thanks a lot.


Ciao
Stephan



  reply index

Thread overview: 162+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-11 18:17 [PATCH v24 00/12] /dev/random - a new approach with full SP800-90B compliance Stephan Müller
2019-11-11 18:18 ` [PATCH v24 01/12] Linux Random Number Generator Stephan Müller
2019-11-11 23:54   ` Thomas Gleixner
2019-11-12  2:25     ` Stephan Müller
2019-11-12 10:16       ` Thomas Gleixner
2019-11-12 22:30   ` kbuild test robot
2019-11-12 23:15     ` Stephan Müller
2019-11-13  0:14   ` kbuild test robot
2019-11-13  0:25     ` Stephan Müller
2019-11-24  4:51   ` Sandy Harris
2019-11-24  9:02     ` Stephan Mueller
2019-11-11 18:19 ` [PATCH v24 02/12] LRNG - allocate one SDRNG instance per NUMA node Stephan Müller
2019-11-11 18:20 ` [PATCH v24 03/12] LRNG - /proc interface Stephan Müller
2019-11-11 18:20 ` [PATCH v24 04/12] LRNG - add switchable DRNG support Stephan Müller
2019-11-11 18:21 ` [PATCH v24 05/12] crypto: DRBG - externalize DRBG functions for LRNG Stephan Müller
2019-11-11 18:21 ` [PATCH v24 06/12] LRNG - add SP800-90A DRBG extension Stephan Müller
2019-11-11 18:22 ` [PATCH v24 07/12] LRNG - add kernel crypto API PRNG extension Stephan Müller
2019-11-11 18:23 ` [PATCH v24 08/12] crypto: provide access to a static Jitter RNG state Stephan Müller
2019-11-11 18:23 ` [PATCH v24 09/12] LRNG - add Jitter RNG fast noise source Stephan Müller
2019-11-11 18:24 ` [PATCH v24 10/12] LRNG - add TRNG support Stephan Müller
2019-11-11 18:26 ` [PATCH v24 11/12] LRNG - add SP800-90B compliant health tests Stephan Müller
2019-11-12 19:58   ` Alexander E. Patrakov
2019-11-12 23:11     ` Stephan Müller
2019-11-13  0:36     ` Stephan Müller
2019-11-13  6:02       ` Alexander E. Patrakov
2019-11-14  1:46         ` Stephan Müller
2019-11-11 18:26 ` [PATCH v24 12/12] LRNG - add interface for gathering of raw entropy Stephan Müller
2019-11-12 20:55   ` kbuild test robot
2019-11-12 23:13     ` Stephan Müller
2019-11-12 13:23 ` [PATCH v24 00/12] /dev/random - a new approach with full SP800-90B compliance Florian Weimer
2019-11-12 22:43   ` Stephan Müller
2019-11-12 15:33 ` Andy Lutomirski
2019-11-12 23:03   ` Stephan Müller
2019-11-12 23:26     ` Stephan Müller
2019-11-13  4:24   ` Stephan Müller
2019-11-13  4:48     ` Andy Lutomirski
2019-11-13 12:16       ` Stephan Müller
2019-11-16  9:32 ` [PATCH v25 00/12] /dev/random - a new approach with full SP800-90B Stephan Müller
2019-11-16  9:33   ` [PATCH v25 01/12] Linux Random Number Generator Stephan Müller
2019-11-16 11:25     ` Thomas Gleixner
2019-11-17 10:30       ` Stephan Müller [this message]
2019-11-16 18:13     ` Nicolai Stange
2019-11-17 11:01       ` Stephan Müller
2019-11-16  9:33   ` [PATCH v25 02/12] LRNG - allocate one SDRNG instance per NUMA node Stephan Müller
2019-11-16  9:34   ` [PATCH v25 03/12] LRNG - /proc interface Stephan Müller
2019-11-16 16:39     ` Andy Lutomirski
2019-11-17 12:16       ` Stephan Müller
2019-11-19 10:06         ` Andy Lutomirski
2019-11-19 10:55           ` Stephan Mueller
2019-11-19 17:40             ` Andy Lutomirski
2019-11-16 23:36     ` Eric W. Biederman
2019-11-17 11:37       ` Stephan Müller
2019-11-16  9:34   ` [PATCH v25 04/12] LRNG - add switchable DRNG support Stephan Müller
2019-11-16  9:35   ` [PATCH v25 05/12] crypto: DRBG - externalize DRBG functions for LRNG Stephan Müller
2019-11-16  9:35   ` [PATCH v25 06/12] LRNG - add SP800-90A DRBG extension Stephan Müller
2019-11-16  9:35   ` [PATCH v25 07/12] LRNG - add kernel crypto API PRNG extension Stephan Müller
2019-11-16  9:36   ` [PATCH v25 08/12] crypto: provide access to a static Jitter RNG state Stephan Müller
2019-11-16  9:36   ` [PATCH v25 09/12] LRNG - add Jitter RNG fast noise source Stephan Müller
2019-11-20 13:33     ` Neil Horman
2019-11-20 20:07       ` Stephan Müller
2019-11-21 14:19         ` Neil Horman
2019-11-21 14:33           ` Stephan Mueller
2019-11-16  9:37   ` [PATCH v25 10/12] LRNG - add TRNG support Stephan Müller
2019-11-16 16:09     ` Andy Lutomirski
2019-11-17 11:10       ` Stephan Müller
2019-11-19 10:07         ` Andy Lutomirski
2019-11-19 10:46           ` Stephan Mueller
2019-11-19 12:41           ` Greg Kroah-Hartman
2019-11-20  8:58             ` Stephan Müller
2019-11-20  9:55               ` Alexander E. Patrakov
2019-11-20 13:29               ` Greg Kroah-Hartman
2019-11-20 19:51                 ` Stephan Müller
2019-11-20 19:57                   ` Alexander E. Patrakov
2019-11-20 20:32                   ` Greg Kroah-Hartman
2019-11-21 13:06                     ` Stephan Müller
2019-11-16  9:37   ` [PATCH v25 11/12] LRNG - add SP800-90B compliant health tests Stephan Müller
2019-11-16  9:38   ` [PATCH v25 12/12] LRNG - add interface for gathering of raw entropy Stephan Müller
2019-11-16 16:51     ` Andy Lutomirski
2019-11-17 22:55       ` Stephan Müller
2019-11-19 10:04         ` Andy Lutomirski
2019-11-19 17:17     ` Randy Dunlap
2019-11-20  9:01       ` Stephan Müller
2019-11-21 12:18     ` Nicolai Stange
2019-11-21 15:18       ` Stephan Müller
2019-11-23 20:08   ` [PATCH v26 00/12] /dev/random - a new approach with full SP800-90B Stephan Müller
2019-11-23 20:10     ` [PATCH v26 01/12] Linux Random Number Generator Stephan Müller
2019-11-24 22:44       ` kbuild test robot
2019-11-25  6:29         ` Stephan Mueller
2019-11-23 20:10     ` [PATCH v26 02/12] LRNG - allocate one SDRNG instance per NUMA node Stephan Müller
2019-11-23 20:11     ` [PATCH v26 03/12] LRNG - sysctls and /proc interface Stephan Müller
2019-11-23 20:11     ` [PATCH v26 04/12] LRNG - add switchable DRNG support Stephan Müller
2019-11-23 20:31     ` [PATCH v26 05/12] crypto: DRBG - externalize DRBG functions for LRNG Stephan Müller
2019-11-23 20:32     ` [PATCH v26 06/12] LRNG - add SP800-90A DRBG extension Stephan Müller
2019-11-23 20:32     ` [PATCH v26 07/12] LRNG - add kernel crypto API PRNG extension Stephan Müller
2019-11-23 20:33     ` [PATCH v26 08/12] crypto: provide access to a static Jitter RNG state Stephan Müller
2019-11-23 20:34     ` [PATCH v26 09/12] LRNG - add Jitter RNG fast noise source Stephan Müller
2019-11-23 20:34     ` [PATCH v26 10/12] LRNG - add TRNG support Stephan Müller
2019-11-23 20:34     ` [PATCH v26 11/12] LRNG - add SP800-90B compliant health tests Stephan Müller
2019-11-23 20:35     ` [PATCH v26 12/12] LRNG - add interface for gathering of raw entropy Stephan Müller
2020-01-09  8:29     ` [PATCH v27 00/12] /dev/random - a new approach with full SP800-90B Stephan Müller
2020-01-09  8:30       ` [PATCH v27 01/12] Linux Random Number Generator Stephan Müller
2020-01-16  6:09         ` kbuild test robot
2020-01-16  6:41           ` Stephan Mueller
2020-01-09  8:31       ` [PATCH v27 02/12] LRNG - allocate one DRNG instance per NUMA node Stephan Müller
2020-01-09  8:31       ` [PATCH v27 03/12] LRNG - sysctls and /proc interface Stephan Müller
2020-01-09  8:32       ` [PATCH v27 04/12] LRNG - add switchable DRNG support Stephan Müller
2020-01-11  7:09         ` kbuild test robot
2020-01-12 10:12           ` Stephan Müller
2020-01-09  8:32       ` [PATCH v27 05/12] crypto: DRBG - externalize DRBG functions for LRNG Stephan Müller
2020-01-09  8:32       ` [PATCH v27 06/12] LRNG - add SP800-90A DRBG extension Stephan Müller
2020-01-09  8:33       ` [PATCH v27 07/12] LRNG - add kernel crypto API PRNG extension Stephan Müller
2020-01-09  8:33       ` [PATCH v27 08/12] crypto: provide access to a static Jitter RNG state Stephan Müller
2020-01-09  8:34       ` [PATCH v27 09/12] LRNG - add Jitter RNG fast noise source Stephan Müller
2020-01-10  0:24         ` Randy Dunlap
2020-01-10  7:45           ` Stephan Mueller
2020-01-09  8:34       ` [PATCH v27 10/12] LRNG - add SP800-90B compliant health tests Stephan Müller
2020-01-10  0:20         ` Randy Dunlap
2020-01-10  8:27           ` Stephan Mueller
2020-01-09  8:35       ` [PATCH v27 11/12] LRNG - add interface for gathering of raw entropy Stephan Müller
2020-01-09  8:35       ` [PATCH v27 12/12] LRNG - add power-on and runtime self-tests Stephan Müller
2020-01-10  0:22         ` Randy Dunlap
2020-01-10  7:48           ` Stephan Mueller
2020-01-13 10:39         ` Dan Carpenter
2020-01-13 10:46           ` Stephan Mueller
2020-01-15 10:31       ` [PATCH v28 00/12] /dev/random - a new approach with full SP800-90B Stephan Müller
2020-01-15 10:31         ` [PATCH v28 01/12] Linux Random Number Generator Stephan Müller
2020-01-16  0:11           ` Randy Dunlap
2020-01-16  7:22             ` Stephan Mueller
2020-01-15 10:32         ` [PATCH v28 02/12] LRNG - allocate one DRNG instance per NUMA node Stephan Müller
2020-01-15 10:32         ` [PATCH v28 03/12] LRNG - sysctls and /proc interface Stephan Müller
2020-01-15 10:32         ` [PATCH v28 04/12] LRNG - add switchable DRNG support Stephan Müller
2020-01-15 10:33         ` [PATCH v28 05/12] crypto: DRBG - externalize DRBG functions for LRNG Stephan Müller
2020-01-15 10:33         ` [PATCH v28 06/12] LRNG - add SP800-90A DRBG extension Stephan Müller
2020-01-16  0:14           ` Randy Dunlap
2020-01-16  6:55             ` Stephan Mueller
2020-01-15 10:34         ` [PATCH v28 07/12] LRNG - add kernel crypto API PRNG extension Stephan Müller
2020-01-16  0:15           ` Randy Dunlap
2020-01-16  6:54             ` Stephan Mueller
2020-01-15 10:34         ` [PATCH v28 08/12] crypto: provide access to a static Jitter RNG state Stephan Müller
2020-01-15 10:34         ` [PATCH v28 09/12] LRNG - add Jitter RNG fast noise source Stephan Müller
2020-01-16  0:17           ` Randy Dunlap
2020-01-16  6:51             ` Stephan Mueller
2020-01-15 10:35         ` [PATCH v28 10/12] LRNG - add SP800-90B compliant health tests Stephan Müller
2020-01-15 10:35         ` [PATCH v28 11/12] LRNG - add interface for gathering of raw entropy Stephan Müller
2020-01-16  0:18           ` Randy Dunlap
2020-01-16  6:43             ` Stephan Mueller
2020-01-16  6:48               ` Randy Dunlap
2020-01-16  6:52                 ` Stephan Mueller
2020-01-15 10:36         ` [PATCH v28 12/12] LRNG - add power-on and runtime self-tests Stephan Müller
2020-01-19 21:12         ` [PATCH v29 00/12] /dev/random - a new approach with full SP800-90B Stephan Müller
2020-01-19 21:13           ` [PATCH v29 01/12] Linux Random Number Generator Stephan Müller
2020-01-19 21:13           ` [PATCH v29 02/12] LRNG - allocate one DRNG instance per NUMA node Stephan Müller
2020-01-19 21:14           ` [PATCH v29 03/12] LRNG - sysctls and /proc interface Stephan Müller
2020-01-19 21:14           ` [PATCH v29 04/12] LRNG - add switchable DRNG support Stephan Müller
2020-01-19 21:15           ` [PATCH v29 05/12] crypto: DRBG - externalize DRBG functions for LRNG Stephan Müller
2020-01-19 21:16           ` [PATCH v29 06/12] LRNG - add SP800-90A DRBG extension Stephan Müller
2020-01-19 21:16           ` [PATCH v29 07/12] LRNG - add kernel crypto API PRNG extension Stephan Müller
2020-01-19 21:17           ` [PATCH v29 08/12] crypto: provide access to a static Jitter RNG state Stephan Müller
2020-01-19 21:18           ` [PATCH v29 09/12] LRNG - add Jitter RNG fast noise source Stephan Müller
2020-01-19 21:18           ` [PATCH v29 10/12] LRNG - add SP800-90B compliant health tests Stephan Müller
2020-01-19 21:19           ` [PATCH v29 11/12] LRNG - add interface for gathering of raw entropy Stephan Müller
2020-01-19 21:20           ` [PATCH v29 12/12] LRNG - add power-on and runtime self-tests Stephan Müller

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