[Bug 206669] Little-endian kernel crashing on POWER8 on heavy big-endian PowerKVM load
From: <hidden>
Date: 2020-02-26 11:12:29
https://bugzilla.kernel.org/show_bug.cgi?id=206669
--- Comment #5 from npiggin@gmail.com ---bugzilla-daemon@bugzilla.kernel.org's on February 26, 2020 8:28 pm:
quoted hunk ↗ jump to hunk
https://bugzilla.kernel.org/show_bug.cgi?id=206669--- Comment #4 from John Paul Adrian Glaubitz (glaubitz@physik.fu-berlin.de)--- (In reply to npiggin from comment #3)quoted
Do you have tracing / ftrace enabled in the host kernel for any reason? Turning that off might let the oops message get printed.Seems that this is the case in the Debian kernel, yes: root@watson:~# grep -i ftrace /boot/config-5.4.0-0.bpo.3-powerpc64le CONFIG_KPROBES_ON_FTRACE=y CONFIG_HAVE_KPROBES_ON_FTRACE=y CONFIG_HAVE_DYNAMIC_FTRACE=y CONFIG_HAVE_DYNAMIC_FTRACE_WITH_REGS=y CONFIG_HAVE_FTRACE_MCOUNT_RECORD=y CONFIG_FTRACE=y CONFIG_FTRACE_SYSCALLS=y CONFIG_DYNAMIC_FTRACE=y CONFIG_DYNAMIC_FTRACE_WITH_REGS=y CONFIG_FTRACE_MCOUNT_RECORD=y # CONFIG_FTRACE_STARTUP_TEST is not set root@watson:~# Do you have the kernel command option at hand which disables ftrace on the command line? Is it just ftrace=off?
Hmm, not sure, Documentation/admin-guide/kernel-parameters.txt seems to say that wouldn't work. I thought it might only be going down that path if you have already done some tracing. Perhaps ensure /sys/kernel/debug/tracing/tracing_on is set to 0, and then `echo 1 > /sys/kernel/debug/tracing/free_buffer` before you start the test.
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FWIW, the kernel image comes from this Debian package:quoted
http://snapshot.debian.org/archive/debian/20200211T210433Z/pool/main/l/linux/linux-image-5.4.0-0.bpo.3-powerpc64le_5.4.13-1%7Ebpo10%2B1_ppc64el.deb Okay. Any chance you could test an upstream kernel?Sure, absolutely. Any preference on the version number?
Current head if you're feeling lucky, but v5.5 if not. But you can give the ftrace test a try with the debian kernel first if you've got it ready to go.
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Don't bother testing that after the above -- panic_on_oops happens after oops_begin(), so it won't help unfortunately.Okay.quoted
Attmepting to get into xmon might though, if you boot with xmon=on. Try that if tracing wasn't enabled, or disabling it doesn't help.Okay. I will try to disable ftrace first, then retrigger the crash.
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