Showstoppers for RPI3

[Mark Millard]

On 2020-Feb-25, at 09:54, bob prohaska <fbsd at www.zefox.net> wrote:

> There seem to be a handful of problems for -current on the RPI3 at
> the moment. Those I've noticed include not getting multicore operation,
> cpu_reset failing and OOMA kills with vm.pfault_oom_attempts="-1" set
> in /boot/loader.conf.

If you are seeing vm.pfault_oom_attempts="-1" fail to work on or
after head -r357253 (from 2020-Jan-29) that is likely new news.
However, for aarch64 RPi*'s, this is after -r356767 where the
kernel needs to be told to avoid touching all the armstub8-gic.bin
or armstub8.bin RAM. (Previously worked only by accident, i.e.,
despite not being told to avoid all that RAM.)

It is messy to make judgments about aarch64 RPi*'s on or after
-r356767 (until/unless all the armstub8*.bin is being reported to
the kernel as RAM to avoid): too much ends up messed up by the
kernel replacing part of armstub8*.bin's RAM content.

The problem -r357253 fixed was for all platforms, not just aarch64,
much less being aarch64 RPi* specific. As far as I've seen, the
platforms that do not have problems at -r356767 are no longer
getting reports of vm.pfault_oom_attempts="-1" problems.

The armstub8-gic.bin/armstub8.bin RAM not being reported to the
kernel as RAM to avoid touching is a known problem for aarch64
RPi*'s. But, as far as I know, no one has indicated that they are
working on getting such RPi*'s to well report armstub8*.bin RAM
to the kernel --or that they are planning to do so.

As far as I know, there is no evidence that the kernel is doing
anything that it should not relative to what has been reported to
it. The problem is aarch64 RPi* specific for what is being
insufficiently reported to the kernel.

> What's a good way to figure out when it's safe(ish) to stick a toe
> back in -current? Are there any relevant bug reports to watch?


For aarch64 RPi*'s, either one sticks to head -r356676 or before
(which is also before -r357026 introduced the
vm.pfault_oom_attempts="-1" failure) or one patches in a work
around for reporting armstub8*.bin RAM to the kernel sufficiently
for now and otherwise uses -r357253 or later. The patch could be
to FreeBSD code or to u-boot code.

In my case, I kept my sysutils/u-boot-rpi4 based investigative
workaround in place: adjusting an efi_add_memory_map use to
change an in-line constant from 1 to 2, indicating to avoid
another page of RAM.

I do *not* have FreeBSD patched for the armstub8-gic.bin RAM
issue at all, just sysutils/u-boot-rpi4 .


===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)