Kernel Error when writing to CAAM Encrypted Partition

[gilmoreat]

We are currently running into an issue were we are getting a kernel error every once in a while when writing to an encrypted partition set up following AN12714 Rev. 2. Sometimes the kernel will report a crash saying "Unable to handle kernel paging request at virtual address". I was able to recreate the crash by using the dd command to write a large file to the encrypted partition. However, it does not seem to cause the crash every time. Below is some more information on our hardware setup:

• i.MX8QM
  • custom board closely resembling the i.MX8QM MEK (same RAM layout/chip/settings)
• linux-imx : lf-6.1.22-2.0.0
• differences from AN12714
  • encrypted.img is 10GB instead of 32MB

Do you have any idea what the cause of this crash could be? is there any issue to how we are using the CAAM?

@rlgagliardo 

[Harvey021]

Have you tried to refer to the <10 Security> Linux user Guide IMX_LINUX_USERS_GUIDE.pdf. an12714 was not recommended.

Regards

Harvey

[gilmoreat]

Thanks for the reply. After further troubleshooting, it looks like it is not specifically tied to the CAAM encryption. I was able to get an crash by just creating 6 threads of "yes > /dev/null". 

I was looking through the IMX8_1N94W errata document and ERR050104 mentioned a cache coherency issue. Could this be related to the crash? Is there already a patch in the kernel to address this issue?

[rlgagliardo]

We had something similar - the issue seemed to be resolved by dropping the clock frequency down from 1.6GHz to 1.3GHz.