Re: [PATCH v5 8/8] hw/vfio: all vfio files can now be common files

On 8/17/2026 11:18 PM, Andreas Grapentin wrote:
> On Mar 18 26, Pierrick Bouvier wrote:
>> -specific_ss.add_all(when: 'CONFIG_VFIO', if_true: vfio_ss)
>> +system_ss.add_all(when: 'CONFIG_VFIO', if_true: vfio_ss)
> 
> Apologies for digging out this old thread, but parts of the vfio code
> need linux/kvm.h, which includes asm/kvm.h. Consequently it can only be
> fully architecture agnostic based on the assumption that KVM will only
> ever be able to support one guest architecture which must be the same as
> the host architecture.
> 
> On s390x, we are currently working on a KVM change that breaks this
> assumption:
> https://lore.kernel.org/all/[email protected]/
> 
> We are in the process of working out what changes this would require on
> the qemu side, and will send a patch series soon for discussion, but
> we've noticed that this patch series in particular was a breaking change
> for us when moving to v11.1.
> 
> Fortunately, this series also extracted the architecture dependent code
> in VFIO into the kvm-helpers.c file, so for us the most obvious solution
> would be to keep kvm-helpers.c in specific_ss, while the rest of vfio
> can go to system_ss. Would that be acceptable?
>

Thanks for asking.

It would be better to keep it as system_ss, since bringing back
specific_ss will break the single-binary compilation.
It should not be needed to rely on target config within the C file
directly. At least, we didn't meet any situation where it was.
That said, there is nothing in CI (yet) that prevent such regression,
but I would appreciate if you could keep it as it is for now.

If you need to filter a specific function per config
(host/target/whatever), the right way is to isolate this in a new file,
and condition inclusion from build system instead.

system_ss.add_all(when: 'CONFIG_X', if_true: [newfile.c])
Also, you can add associated stubs for other configs in stub_ss.
stub_ss.add(files('newfile-stubs.c'))

I don't know the details of the series you sent (and too big for me to
take a look now), but if you have a precise question on a specific
patch, feel free to reach out to me by email.

> Thanks,
> Andreas
> 

Regards,
Pierrick