[libvirt] [Qemu-devel] pvpanic plans?

[Peter Maydell]

On 22 August 2013 21:09, Anthony Liguori <anthony at codemonkey.ws> wrote:
> Paolo Bonzini <pbonzini at redhat.com> writes:
>> Not just that.  Panic notifiers are called in a substantially unknown
>> environment, with locks taken or interrupts already set up.
>
> If you make the panic notify a config space write, then on virtio-pci,
> it's an outb to a fixed offset within a io address that after boot is
> static.
>
> So the address could be stored in a global and accessed without a lock.

Fine for virtio-mmio too, obviously. I have a vague recollection that
config space writes on virtio-s390 are weird though. (would also
be an issue if we wanted to implement the virtio-console "emergency
write" functionality.)

-- PMM