Re: [PATCH v1 4/6] vfio-pci/zdev: Setup a zpci memory region for error information

[Farhan Ali]

On 8/13/2025 1:30 PM, Alex Williamson wrote:
> On Wed, 13 Aug 2025 10:08:18 -0700
> Farhan Ali <alifm@xxxxxxxxxxxxx> wrote:
> > diff --git a/include/uapi/linux/vfio_zdev.h b/include/uapi/linux/vfio_zdev.h
> > index 77f2aff1f27e..bcd06f334a42 100644
> > --- a/include/uapi/linux/vfio_zdev.h
> > +++ b/include/uapi/linux/vfio_zdev.h
> > @@ -82,4 +82,9 @@ struct vfio_device_info_cap_zpci_pfip {
> >   	__u8 pfip[];
> >   };
> >   
> > +struct vfio_device_zpci_err_region {
> > +	__u16 pec;
> > +	int pending_errors;
> > +};
> > +
> >   #endif
> If this is uapi it would hopefully include some description, but if
> this is the extent of what can be read from the device specific region,
> why not just return it via a DEVICE_FEATURE ioctl?  Thanks,
>
> Alex
Yes, will add more details about the uapi. My thinking was based on how 
we expose some other vfio device information on s390x, such as SCHIB for 
vfio-ccw device.

I didn't think about the DEVICE_FEATURE ioctl. But looking into it, it 
looks like we would have to define a device feature (for eg: 
VFIO_DEVICE_FEATURE_ZPCI_ERROR), and expose this information via 
GET_FEATURE? If the preference is to use the DEVICE_FEATURE ioctl I can 
try that. Curious, any specific reason you prefer the DEVICE_FEATURE 
ioctl to the memory region?

Thanks
Farhan