[dm-devel] dm-integrity stalls with iMX6q CAAM

[Neil Armstrong]

On 17/10/2018 15:35, Horia Geanta wrote:
> On 9/21/2018 3:06 PM, Neil Armstrong wrote:
>> Hi,
>>
>> I recently configured dm-crypt + dm-integrity on an iMX6q platform with CAAM Hash functions enabled using the following command lines :
>>
>> Linux 4.14.71
>>
>> cryptsetup luksFormat /dev/mmcblk1p3 --cipher aes-xts-plain64 --type luks2 --integrity hmac-sha256 --sector-size 512 --use-urandom
>> cryptsetup open /dev/mmcblk1p3 root
>> mkfs.ext4 -v -F /dev/mapper/root
>>
>> luksFormat and open finishes correctly, luksDump and status reports correct dm and luks properties.
>>
>> but when trying to access the /dev/mapper/root (mkfs, sha256sum or whatever), it blocks without any warning or errors reported by the kernel.
>> I can see a few (~170) interrupts on the jr0 interrupt then nothing.
>>
>> Is there a particular issue with hmac-sha256 with the linux CAAM driver ?
>>
>> When disabling the CAAM hash functions or using another cipher & integrity pair, it works like a charm.
>>
> The issue you are seeing is most probably related to CAAM driver not
> implementing correctly the crypto requests "backlogging".
> See commit c0403ec0bb5a ("Revert "dm crypt: fix deadlock when async crypto
> algorithm returns -EBUSY"") for a detailed description.
> 
> Historically, there have been several CAAM backlogging implementations proposed
> - but all were rejected:
> v1: https://patchwork.kernel.org/patch/7144701
> v2: https://patchwork.kernel.org/patch/7199241
> v3: https://patchwork.kernel.org/patch/7221941
> v4: https://patchwork.kernel.org/patch/7230241
> v5: https://patchwork.kernel.org/patch/9033121
> 
> Discussion here: https://community.nxp.com/message/1020096
> mentions v2 as solving the issue.
> You could try it while we find a solution that would be accepted upstream.
> 
> Hope this helps,
> Horia
> 

Hi Horia,

Thanks for the pointers ! Hopefully you will find a solution soon.

Neil