Re: 'make check-tcg' fails with an assert in qemu_plugin_vcpu_init_hook

[Peter Maydell]

On Wed, 21 Jun 2023 at 11:00, Alex Bennée <alex.bennee@linaro.org> wrote:
>
>
> Peter Maydell <peter.maydell@linaro.org> writes:
>
> > On Wed, 21 Jun 2023 at 09:05, Alex Bennée <alex.bennee@linaro.org> wrote:
> >>   - I suspect the plugin core stuff could be build once (or maybe twice,
> >>     system and user)
> >
> > It is already build-once, that's why it goes wrong...
>
> I thought it was the other way around:
>
>   specific_ss.add(when: 'CONFIG_PLUGIN', if_true: [files(
>     'loader.c',
>     'core.c',
>     'api.c',
>   ), declare_dependency(link_args: plugin_ldflags)])
>
> but if we built it for linux-user and softmmu this could be fixed (until
> the next breakage anyway). cpus-common.c is the common code that sets
> this once.

Oh, right, I got it the wrong way around.

> >>   - we need to have some guard rails somehow to make sure things don't
> >>     go out of sync
> >
> > We do, this is the poison.h stuff. CONFIG_USER_ONLY is a
> > special case which we don't poison because there would be
> > too much refactoring required...
>
> I guess a great big honking comment at the top of CPUState telling
> people not to do that or pushing softmmu and user specific bits of
> CPUState into their own de-referenced structures.

It's not specific to CPUState, though. The thing you must not
do is use CONFIG_USER_ONLY (or CONFIG_SOFTMMU, now) to ifdef
out any struct field anywhere in any struct that's visible to
compiled-once code, or otherwise do something that changes
the ABI of a global or of a type passed around between functions.

-- PMM