Re: [PATCH] accel/kvm/kvm-all: Handle register access errors

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

On Thu, 1 Dec 2022 at 10:27, Akihiko Odaki <akihiko.odaki@daynix.com> wrote:
>
> A register access error typically means something seriously wrong
> happened so that anything bad can happen after that and recovery is
> impossible.
> Even failing one register access is catastorophic as
> architecture-specific code are not written so that it torelates such
> failures.
>
> Make sure the VM stop and nothing worse happens if such an error occurs.
>
> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>

In a similar vein there was also
https://lore.kernel.org/all/20220617144857.34189-1-peterx@redhat.com/
back in June, which on the one hand was less comprehensive but on
the other does the plumbing to pass the error upwards rather than
reporting it immediately at point of failure.

I'm in principle in favour but suspect we'll run into some corner
cases where we were happily ignoring not-very-important failures
(eg if you're running Linux as the host OS on a Mac M1 and your
host kernel doesn't have this fix:
https://lore.kernel.org/all/YnHz6Cw5ONR2e+KA@google.com/T/
then QEMU will go from "works by sheer luck" to "consistently
hits this error check"). So we should aim to land this extra
error checking early in the release cycle so we have plenty of
time to deal with any bug reports we get about it.

thanks
-- PMM