Re: qemu-system-aarch64 hangs in a cortex-a72 test

[Peter Maydell <peter.maydell@linaro.org>]

On Sun, 5 Oct 2025 at 17:55, Liviu Ionescu <ilg@livius.net> wrote:
>
> Hi!
>
> I have a small semihosted test that I use to test the xPack QEMU releases.
>
> The test worked just fine up to 8.2.9, but hangs with 9.0.0 or later, including 10.0.0.

> Any ideas what changed from 8.x to 9.0 to cause this?

Notably 9.0 is the first release which included
commit 59754f85ed, which enforces the architectural
requirement that when the MMU is disabled unaligned
loads and stores must fault. We didn't use to check
that, so bare metal code that was compiled with a
compiler that assumes unaligned accesses are permitted
(or which simply has a bug where it does an unaligned
access not permitted by the C spec) will now take an
exception where it didn't before. (You should be able
to see that in the -d debug logs if it's happening,
or via gdbstub if you put a breakpoint on the exception
entry point.)

If it doesn't look like that's what it's falling over on,
you could try a git bisect of QEMU to pinpoint the
commit where it stopped working.

thanks
-- PMM