Re: [PATCH v5 7/9] vfio/pci: Clean up BAR zap and revocation

[Matt Evans <matt@ozlabs.org>]

Hi Alex,

On 04/08/2026 21:10, Alex Williamson wrote:
> On Thu, 30 Jul 2026 15:47:13 +0100
> Matt Evans <matt@ozlabs.org> wrote:
> 
>> Hi Alex,
>>
>> On 29/07/2026 18:52, Alex Williamson wrote:
>>> On Wed, 15 Jul 2026 18:47:30 +0100
>>> Matt Evans <matt@ozlabs.org> wrote:  
>>>> diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
>>>> index 9a1674c152aa..e2b4252e7c3f 100644
>>>> --- a/include/linux/vfio_pci_core.h
>>>> +++ b/include/linux/vfio_pci_core.h
>>>> @@ -134,6 +134,7 @@ struct vfio_pci_core_device {
>>>>  	bool			pm_intx_masked;
>>>>  	bool			pm_runtime_engaged;
>>>>  	bool			sriov_active;
>>>> +	bool			zap_bars_on_revoke;
>>>>  	struct pci_saved_state	*pci_saved_state;
>>>>  	struct pci_saved_state	*pm_save;
>>>>  	int			ioeventfds_nr;  
>>>
>>> This should be in the bitfield usage group since it's only modified at
>>> init time.  
>>
>> This was intentional, but happy to change it if you're certain ofc.  Is
>> it inconceivable that a sub-driver could set it after init?  I'd say
>> they _shouldn't_, but only review will stop them and this placement
>> intended to be cautious.  It seemed a low cost way to avoid issues
>> around synchronisation on the bitfield.
> 
> I'd agree with the statement that they shouldn't, it would be difficult
> to synchronize setting the flag once there are any active mappings of
> the BARs.  Also, if we put it in the bitfield category under the
> comment that the value is only modified at setup/release, it documents
> the intentions, hopefully to the extent the author or reviewers notice.
> An argument can always be made to change it if there's a worthwhile use
> case.  Thanks,

Okay, book removed in favour of bit.

Thanks,


Matt