/dev/crypto not being used in 12-STABLE

John Baldwin jhb at FreeBSD.org
Thu Dec 6 23:39:11 UTC 2018

On 12/6/18 3:24 PM, John Nielsen wrote:
>> On Dec 6, 2018, at 4:04 PM, Xin LI <delphij at gmail.com> wrote:
>> On Thu, Dec 6, 2018 at 11:37 AM John Nielsen <lists at jnielsen.net> wrote:
>>> I have upgraded two physical machines from 11-STABLE to 12-STABLE recently (one is 12.0-PRERELEASE r341380 and the other is 12.0-PRERELEASE r341391). I noticed today that neither machine seems to be utilizing /dev/crypto. Typically I see at least ssh/sshd have the device open plus some programs from ports. But 'fuser' doesn't list any processes on either machine:
>>> # fuser /dev/crypto
>>> /dev/crypto:
>>> Both machines are running custom kernels that include "device crypto" and "device cryptodev". One of them additionally has "device aesni".
>>> Is anyone else seeing this? Any idea what would cause it?
>> Your average OpenSSL applications should not use /dev/crypto, if your
>> goal is to utilize AES-NI (which does not require /dev/crypto).  On
>> capable systems, AES-NI would be used automatically (and it's faster
>> this way).
> Thanks for the response. Is there a way to verify that AES-NI is being used for e.g. ssh? I'm also curious why/when/how the change to not use (or support?) /dev/crypto from base openssl was made.

I suspect it was something we just didn't test in the flurry of other work
during the OpenSSL upgrade.  However, it is much faster to use the AES-NI
instructions in userland than to use a system call that copies the data
into a kernel buffer, uses the sames AES-NI instructions, then copies the
data back out again along with the overhead of a pair of user <--> kernel
transitions.  If you have an actual crypto offload device (as in a PCI-e
card or something), then you might be interested in /dev/crypto (and we
should fix that eventually), but AES-NI is just faster software crypto and
is best done directly in userland.

John Baldwin


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