Re: pvpanic mmio support

[Peter Maydell <peter.maydell@linaro.org>]

On Tue, 13 Oct 2020 at 21:37, Mihai Carabas <mihai.carabas@oracle.com> wrote:
> Does anyone know if there is any progress with pvpanic patches that
> brings in mmio support [1]?

I don't think so. If I recall correctly there was quite a lot
of discussion on at least one version of that patchset, and it
was never clear to me at least that having an MMIO pvpanic device
was actually useful (as opposed to for instance having a PCI
device, or maybe a virtio backend, both of which have the
virtue of being (a) pluggable by the user and (b) autodetectable
by the guest).

> I see no activity since late 2018, but I do
> see support added to the kernel (also asking myself how this was tested):
>
> 46f934c misc/pvpanic: add support to get pvpanic device info FDT
> b1d9d6c dt-bindings: misc/pvpanic: add document for pvpanic-mmio
> 725eba2 misc/pvpanic: add MMIO support

That was probably tested with somebody's not-actually-in-QEMU
patchset. The documentation in the kernel's
Documentation/devicetree/bindings/misc/pvpanic-mmio.txt
is just wrong when it says
# QEMU's emulation / virtualization targets provide the following
# PVPANIC MMIO Configuration interface on the "virt" machine.

because we definitely do not.

thanks
-- PMM