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

["Alex Bennée" <alex.bennee@linaro.org>]

Peter Maydell <peter.maydell@linaro.org> writes:

> On Tue, 20 Jun 2023 at 17:56, Peter Maydell <peter.maydell@linaro.org> wrote:
>>
>> $ make -C build/x86 check-tcg
>> make: Entering directory '/mnt/nvmedisk/linaro/qemu-from-laptop/qemu/build/x86'
>> [...]
>>   TEST    munmap-pthread on arm
>> **
>> ERROR:../../plugins/core.c:221:qemu_plugin_vcpu_init_hook: assertion
>> failed: (success)
>> **
>> ERROR:../../accel/tcg/cpu-exec.c:1024:cpu_exec_setjmp: assertion
>> failed: (cpu == current_cpu)
>
> git bisect blames commit d7ee93e2435970:
>
>     cputlb: Restrict SavedIOTLB to system emulation
>
> I think that commit is not correct, because it means that
> the size of 'struct CPUState' and also the offset of fields
> like 'cpu_index' will be different for files which are
> compile-per-target-for-usermode and files which are
> compile-once-only. The assert happens here because the
> code which sets up cpu_index is build-once, but the code
> in qemu_plugin_vcpu_init_hook() which reads cpu_index is
> build-per-target and now they don't agree about where in
> the struct the field is...

Hmm two things from that imply:

  - I suspect the plugin core stuff could be build once (or maybe twice,
    system and user)

  - we need to have some guard rails somehow to make sure things don't
    go out of sync

>
> Reverting the commit fixes the bug.
>
> thanks
> -- PMM


-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro