Re: arm: warning at virt/kvm/arm/vgic.c:1468

Jan Kiszka
2015-02-15T08:48:29Z

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On 2015-02-13 07:53, Alex Bennée wrote:
>
> Alex Bennée <alex.bennee@linaro.org> writes:
>
>> Christoffer Dall <christoffer.dall@linaro.org> writes:
> <snip>
>>> On Sun, Feb 08, 2015 at 08:48:09AM +0100, Jan Kiszka wrote:
> <snip>
>>>> BTW, KVM tracing support on ARM seems like it requires some care. E.g.:
>>>> kvm_exit does not report an exit reason. The in-kernel vgic also seems
>>>> to lack instrumentation. Unfortunate. Tracing is usually the first stop
>>>> when KVM is stuck on a guest.
>>>
>>> I know, the exit reason is on my todo list, and Alex B is sitting on
>>> trace patches for the gic. Coming soon to a git repo near your.
>>
>> For the impatient the raw patches are in:
>>
>> git.linaro.org/people/alex.bennee/linux.git
>> migration/v3.19-rc7-improve-tracing
>
> OK try tracing/kvm-exit-entry for something cleaner.

Doesn't build for ARM (vcpu_sys_reg is ARM64-only so far).

But the values traced seem useful. Wei Huang's patch in kvm.git queue
traces the exception class, but unfortunately nothing else. When would
we need that class? Do we need it at all?

In any case, please add symbolic printing of the magic values whenever
possible, just like on x86.

I'm now throwing trace_printk at my broken KVM. Already found out that I
get ARM_EXCEPTION_IRQ every few 10 µs. Not seeing any irq_* traces,
though. Weird.

Thanks,
Jan

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