Various panics while using HWPMC on ARM64

[Zbigniew Bodek]

Hello,

I encountered some problems with FreeBSD on ARM64 while using hwpmc.
Some of the errors that I found are listed below:

* panic: Unknown kernel exception 0 esr_el1 2000000
* panic: data abort in critical section or under mutex
* panic: VFP exception in the kernel
* panic: Unknown kernel exception 21 esr_el1 86000006

Something is obviously broken.

This can be easily reproduced by invoking for example:
$ pmcstat -S CPU_CYCLES -O cpu_cycles.pmc

wait ~30 seconds or more and hit ctrl + C

Platform: ThunderX CRB (single socket)
SVN rev: 291651
Kernel: GENERIC + "device hwpmc" - "some debugging options"
(also verified that GENERIC + "device hwpmc" does the same)

Logs + patch for GENERIC conf. + kernel binary + objdumped kernel:
https://people.freebsd.org/~zbb/arm64/armv8_panic.tar.gz

Kind regards