Re: [PATCH] hw/arm: virt: Add SBSA watchdog

[Peter Maydell]

On Thu, 5 May 2022 at 11:17, Jan Kiszka <jan.kiszka@siemens.com> wrote:
>
> On 05.05.22 10:40, Peter Maydell wrote:
> > On Sun, 1 May 2022 at 19:07, Jan Kiszka <jan.kiszka@web.de> wrote:
> >>
> >> From: Jan Kiszka <jan.kiszka@siemens.com>
> >>
> >> The virt machine lacks a watchdog so far while the sbsa-ref has a simple
> >> model that is also supported by Linux and even U-Boot. Let's take it to
> >> allow, e.g., system integration tests of A/B software update under
> >> watchdog monitoring.
> >>
> >> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> >
> > The virt board has a PCI bus, and QEMU has a model of a
> > PCI watchdog device -- the i6300esb. Can you use that?
>
> While one could do that, it implies using completely alien Intel x86
> host controller bits on this platform. And, thus, would require changes
> in firmware (e.g. adding a driver to U-Boot).

> > In general I much prefer it if we can support use cases in
> > virt via pluggable PCI devices rather than hard-wired MMIO
> > devices -- it means that only users who want the functionality
> > need to have the exposed attack surface area of the device
> > present in their VM.
>
> Valid point - would making this opt-in via a machine feature be sufficient?

I really strongly prefer the PCI device solution. If you don't
like the i6300esb you could write a model of some other
PCI device.

thanks
-- PMM