Re: [RFC PATCH 18/18] hw/core/qdev: Display warning for devices missing migration state

[Peter Maydell]

On Fri, 3 Jul 2020 at 21:19, Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
>
> When built with --enable-qdev-debug, QEMU displays warnings
> listing devices missing migration state:
>
>   $ qemu-system-arm -S -M spitz
>   qemu-system-arm: warning: missing migration state for type: 
> 'pxa270-c0-arm-cpu'
>   qemu-system-arm: warning: missing migration state for type: 'serial'
>   qemu-system-arm: warning: missing migration state for type: 'pxa2xx-pcmcia'
>   qemu-system-arm: warning: missing migration state for type: 'pxa2xx-pcmcia'
>   qemu-system-arm: warning: missing migration state for type: 
> 'pxa2xx-i2c-slave'
>   qemu-system-arm: warning: missing migration state for type: 
> 'pxa2xx-i2c-slave'
>   qemu-system-arm: warning: missing migration state for type: 'ads7846'
>   qemu-system-arm: warning: missing migration state for type: 'max1111'
>
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
> RFC because there might be something simpler than --enable-qdev-debug.

I think where we'd like to get to is installing a migration
blocker if the machine has any devices which don't have a vmsd.
But for that we'd need to be pretty sure we'd got all the devices
on machines where we care about migration, and we're clearly a
fair way from that (eg we need to do something about the
devices like the CPU which don't have a vmsd but handle their
migration some other way so they don't trigger the condition
for warning/migration-blocker).

I don't have a strong objection to this --enable-qdev-debug, I guess.
Another option halfway between this and a full migration-blocker
would be do a warn_report() for the relevant devices when savevm
tries to migrate them.

thanks
-- PMM