Re: [PATCH v2] pci: Assert that capabilities never overlap

[Markus Armbruster]

Akihiko Odaki <akihiko.odaki@daynix.com> writes:

> pci_add_capability appears most PCI devices. Its error handling required
> lots of code, and led to inconsistent behaviors such as:
> - passing error_abort
> - passing error_fatal
> - asserting the returned value
> - propagating the error to the caller
> - skipping the rest of the function
> - just ignoring
>
> The code generating errors in pci_add_capability had a comment which
> says:
>> Verify that capabilities don't overlap.  Note: device assignment
>> depends on this check to verify that the device is not broken.
>> Should never trigger for emulated devices, but it's helpful for
>> debugging these.
>
> Indeed vfio has some code that passes capability offsets and sizes from
> a physical device, but it explicitly pays attention so that the
> capabilities never overlap.

I can't see that at a glance.  Can you give me a clue?

>                             Therefore, we can always assert that
> capabilities never overlap when pci_add_capability is called, resolving
> these inconsistencies.
>
> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>