linux-kernel - Re: WARNING: CPU: 0 PID: 1111 at arch/arm64/kernel/fpsimd.c:464 fpsimd

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Message-ID: <Y3NwuOKJXudb9K30@sirena.org.uk>
Date:   Tue, 15 Nov 2022 10:58:00 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Naresh Kamboju <naresh.kamboju@...aro.org>,
        open list <linux-kernel@...r.kernel.org>,
        linux-stable <stable@...r.kernel.org>,
        lkft-triage@...ts.linaro.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Ard Biesheuvel <ardb@...nel.org>
Subject: Re: WARNING: CPU: 0 PID: 1111 at arch/arm64/kernel/fpsimd.c:464
 fpsimd_save+0x170/0x1b0

On Tue, Nov 15, 2022 at 09:22:53AM +0100, Arnd Bergmann wrote:

> Have you tried what happens if you run the same thing on an x86
> machine? I would expect them to behave the same way, but it's
> possible something goes wrong with the guest CPU if this ends
> up using some (but not all) of the logic from KVM that would
> use '-cpu host' instead of '-cpu max'. Note that the Neoverse
> CPU in the Altra machine does not support SVE.

I'm finding it hard to think of a failure pattern that would
make it through VL discovery then fail at runtime but also not
obviously trigger any issues in syscall-abi...

> Other things you could easily try would use the same command
> line as above, with the possible combinations of '-cpu host'
> (replacing -cpu max) and '-enable-kvm'. Do you always get
> the same result?

The machine parameter accel={tcg,kvm} is useful for forcing a
specific backend - it's probably wise to force TCG if you might
be running on a job on a native architecture.

BTW there's some other funky stuff going on with that job, the
syscall-abi test is stopped with a timeout after 45 seconds (as
is sve-ptrace) which appears to be coming from a harness
somewhere.  The selection of FP tests run seems to miss fp-stress
too.

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