Re: git: 32a2fed6e71f - stable/13 - openssl: Fix detection of ARMv7 and ARM64 CPU features

On 11/25/2021 10:31 AM, Helge Oldach wrote:
> Allan Jude wrote on Thu, 25 Nov 2021 16:09:25 +0100 (CET):
>> On 11/25/2021 2:38 AM, Helge Oldach wrote:
>>> hmo@p48 ~ $ for f in 0 1 2 3 8 16 32 64 128 ; do echo -n $f:; env OPENSSL_armcap=$f openssl speed -evp aes-256-gcm 2>&1 | tail -1 | cut -wf7; done
>>> 0:42295.15k
>>> 1:23891.19k
>>> 2:42208.57k
>>> 3:23970.56k
>>> 8:42354.98k
>>> 16:42199.06k
>>> 32:size
>>> Illegal instruction (core dumped)
>>> 64:42322.42k
>>> 128:42275.00k
>>> hmo@p48 ~ $
>>>
>>> So I guess HWCAP_FP is the culprit? Maybe related to hard/soft floating
>>> point math which indeed is kind of special on the Pi?
>>
>> So yeah, the issue seems to be that floating point on the RPi4 is slower
>> than not, but now openssl (properly) detects that the CPU advertises
>> support for it.
>>
>> As seen elsewhere in the thread, most other ARM platforms get a very
>> significant speed boost.
> 
> So can we disable FP within OpenSSL for the RPi by default? This commit
> basically introduced a regression for this platform and I think that
> should be fixed.
> 
> Or it the root cause a suboptimal FP implementation that is not adequate
> for the RPi?
> 
> Kind regards
> Helge
> 

The root cause is that the RPi4 advertises support for FP, but its FP is 
slow.

I don't know that there is an easy way to detect the RPi4 specifically. 
You might be able to just disable the FP bit by setting 
OPENSSL_armcap=~1 globally, or maybe via openssl.conf?

-- 
Allan Jude