Re: what is qemu_system_guest_panicked() for?

[Cornelia Huck <cohuck@redhat.com>]

On Mon, Jul 13 2026, Daniel P. Berrangé <berrange@redhat.com> wrote:

> On Mon, Jul 13, 2026 at 10:57:58AM +0200, Markus Armbruster wrote:
>> Daniel P. Berrangé <berrange@redhat.com> writes:
>> 
>> > On Fri, Jul 10, 2026 at 05:02:53PM +0100, Peter Maydell wrote:
>> 
>> [...]
>> 
>> >> So I guess my question is, is it OK to mash these two categories of
>> >> "we can't keep running the VM" together, or should we define a new
>> >> one for the "unrecoverable guest error" case, or do we already have
>> >> some better thing to do that I missed?
>> >
>> > IMHO we should NOT be abusing "panicked" for cases which are
>> > not guest OS panics.
>> 
>> Point.
>> 
>> > Adding new QMP events is cheap and we should do so.
>> 
>> Changing the event sent on a certain situation is technically a
>> compatibility break.  Would it matter here?
>
> What wins "compat break" or "bug fix" ? A strict POV prevents almost
> any bug fixes, if you want to remain bug-for-bug compatible with
> old QEMU.
>
> With my "management app" hat on, I want QEMU to stop sending panic
> events for things that are not panics, as that is triggering incorrect
> actions / admin activities. ie on a panic, I'm going to take a guest
> memory dump and try to analyse what is broken in the guest kernel.

That would argue for e.g. a guest exception loop being a "panic" as
well, as the admin may want to debug that.

>
> The QAPI spec says:
>
>   ##
>   # @GUEST_PANICKED:
>   #
>   # Emitted when guest OS panic is detected
>
>
> and
>
>   ##
>   # @RunState:
>   #
>   # An enumeration of VM run states.
>   #
>   ..
>   # @guest-panicked: guest has been panicked as a result of guest OS
>   #     panic
>
>
> I don't think "machine check exception" or "unknown VM exit"
> can be said to match either of those docs, and thus fixing
> compliance should trump bug-for-bug compatibility IMHO.

I'm wondering whether we first need to agree upon a common definition of
what a "guest OS panic" is. "The Linux kernel ran into a panic()
statement" clearly is; is "the guest OS put itself into a state of which
the only way out is a reboot" a "guest OS panic" as well, or only in
some cases?