linux-kernel - Re: Decreasing time for `rsa

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Message-ID: <6e722409-07d6-79b9-3e8f-d20ae88c0b91@infradead.org>
Date:   Tue, 26 Dec 2017 13:49:36 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Paul Menzel <pmenzel+linux-crypto@...gen.mpg.de>,
        Stephan Müller <smueller@...onox.de>
Cc:     linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Decreasing time for `rsa_init`

On 12/26/2017 12:28 AM, Paul Menzel wrote:
> Dear Stephan, dear Linux folks,
> 
> 
> Am 13.07.2017 um 20:20 schrieb Paul Menzel:
> 
>> Am Mittwoch, den 12.07.2017, 19:38 +0200 schrieb Paul Menzel:
>>
>>> On 07/12/17 19:28, Stephan Müller wrote:
>>>> Am Mittwoch, 12. Juli 2017, 12:59:58 CEST schrieb Paul Menzel:
>>>>> Building CRYPTO_RSA not as module, but into the Linux kernel,
>>>>> `rsa_init()` takes 130 ms on an ASRock E350M1.
>>>>>
>>>>> (Timings are shown by adding `initcall_debug` to Linux command
>>>>> line [1].
>>>>> The times are visualized by `analyze_boot.py` from pm-graph [2]
>>>>> or `systemd-bootchart`.)
>>>>>
>>>>> This is quite a lot of time compared to other modules, and I
>>>>> wonder if
>>>>> there are ways to decrease that time other than building it as a
>>>>> module,
>>>>> and not signing modules?
>>>>
>>>> Is the testmgr compiled? If yes, the self test may take that time.
>>>
>>> It looks like it is, as the tests are not disabled.
>>>
>>> ```
>>> $ grep MANAGER_DISABLE_TESTS .config
>>> # CONFIG_CRYPTO_MANAGER_DISABLE_TESTS is not set
>>> ```
>>>
>>> I’ll try an image without the tests, and will report back.
>>
>> Thank you. That was it. Disabling the tests reduces the time to 51 μs.
>>
>> ```
>> kernel: calling  rsa_init+0x0/0x40 @ 1
>> kernel: initcall rsa_init+0x0/0x40 returned 0 after 51 usecs
>> ```
>>
>> It’d be nice to be able to disable the testmgr during run-time by
>> adding an option to the Linux Kernel command line for example.
> 
> To follow up with this, thanks to commit 9e5c9fe4 (crypto: testmgr - Add a flag allowing the self-tests to be disabled at runtime.), present since Linux 4.7, this can be disabled at run-time by adding `cryptomgr.notests` to the Linux command line.
> 
> I just don’t know, how a user should find this parameter, that means, what module(?) this parameter belongs to, and is visible with `modinfo <module_name>`.

in Documentation/admin-guide/kernel-parameters.txt, we have:

	cryptomgr.notests
                        [KNL] Disable crypto self-tests


I don't have a module built for it, but algboss.o and testmgr.o are combined
(by Makefile) into cryptomgr.o -> cryptomgr.ko, so 'modinfo cryptomgr.ko'
should provide the module parameters since testmgr.c contains:

static bool notests;
module_param(notests, bool, 0644);
MODULE_PARM_DESC(notests, "disable crypto self-tests");


> Additionally in `crypto/algboss.c`, that parameter doesn’t seem to apply.

Right, it only pays attention to the build-time Kconfig symbol
CRYPTO_MANAGER_DISABLE_TESTS.  It would be preferable to have consistency.


-- 
~Randy