Re: what is qemu_system_guest_panicked() for?

[Aditya Gupta <adityag@linux.ibm.com>]

+ shivang


On 13/07/26 19:06, Fabiano Rosas wrote:

> Peter Maydell <peter.maydell@linaro.org> writes:
>
>> (cc list is a random mix of maintainers of code that calls this
>> function, Paolo as "main loop maintainer" and a few others who
>> I thought might have an opinion.)
>>
>> We have a qemu_system_guest_panicked() function which causes QEMU
>> to report this to the user and do one of a couple of possible options
>> (shutdown, pause the VM, do nothing). This seems mostly intended for
>> "the guest OS told us by some mechanism that it just panicked". But
>> we use it more widely than that...
>>
>> Cases which are "the guest told us about a panic":
>>   - accel/kvm/kvm-all.c handling of the KVM_EXIT_SYSTEM_EVENT SEV_TERM
>>     and CRASH subtypes
>>   - the pvpanic device
>>   - the spapr ibm,os-term RTAS call
> I think I remember this one is arbitrary and the spec doesn't really
> interprets this as an error state of any sort. It's just that this is
> the way it has been used.
>
> I had to comment that qemu_system_guest_panicked line a few times when
> experimenting with using os-term to do a clean termination _from_ the
> guest code.
>
> PPC folks, please confirm, it's been years since I looked at this.
True. The way the spec mentions it seems the OS can get control back after
execution of ibm,os-term.

This difference is noticeable with `panic=15`. On an LPAR, this would 
print the
following line and do a reboot after a timeout of 15s (this happens in linux
after it has done the os-term call):

     [  338.186072] Rebooting in 15 seconds..

But on QEMU, this isn't printed, and the machine powers down:

     qemu-system-ppc64: OS terminated:

Maybe worth taking a look. Didn't notice this earlier, thanks Fabiano !

- Aditya G