Re: [PATCH v5 00/13] riscv: improve boot time isa extensions handling

[Guenter Roeck]

On 2/12/23 10:45, Conor Dooley wrote:
...
> > However, I still see that the patch series
> > results in boot hangs with the sifive_u qemu emulation, where
> > the log ends with "Oops - illegal instruction". Is that problem
> > being addressed as well ?
>
> Hmm, if it died on the last commit in this series, then I am not sure.
> If you meant with riscv/for-next or linux-next that's fixed by a patch
> from Samuel:
> https://patchwork.kernel.org/project/linux-riscv/patch/20230212021534.59121-3-samuel@xxxxxxxxxxxx/

It failed after the merge, so it looks like it may have been merge damage.

Anyway, I applied

RISC-V: Don't check text_mutex during stop_machine
riscv: Fix early alternative patching
riscv: Fix Zbb alternative IDs

and the sifive_u emulation no longer crashes. However, I still get

[    0.000000] ------------[ cut here ]------------
[    0.000000] WARNING: CPU: 0 PID: 0 at arch/riscv/kernel/patch.c:71 patch_insn_write+0x222/0x2f6

repeated several times.

I then also tested

riscv: patch: Fixup lockdep warning in stop_machine
riscv: Fix early alternative patching
riscv: Fix Zbb alternative IDs

which works fine (no warning backtrace) for sifive_u, but gives me

WARNING: CPU: 0 PID: 0 at kernel/trace/trace_events.c:433 trace_event_raw_init+0xde/0x642

and a whole lot of

event btrfs_clear_extent_bit has unsafe dereference of argument 1

and similar messages when running the "virt" emulation. That was there before,
but drowned in the noise. Ok, guess I'll need another round of bisect.

Guenter