Re: [PATCH v18 2/4] vfio-pci/zdev: Add a device feature for error information

[Farhan Ali]

On 6/3/2026 3:37 PM, Alex Williamson wrote:
> On Wed,  3 Jun 2026 11:24:13 -0700
> Farhan Ali <alifm@xxxxxxxxxxxxx> wrote:
> > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> > index 5de618a3a5ee..3eead86a00ab 100644
> > --- a/include/uapi/linux/vfio.h
> > +++ b/include/uapi/linux/vfio.h
> > @@ -1534,6 +1534,36 @@ struct vfio_device_feature_dma_buf {
> >    */
> >   #define VFIO_DEVICE_FEATURE_MIG_PRECOPY_INFOv2  12
> >   
> > +/**
> > + * VFIO_DEVICE_FEATURE_ZPCI_ERROR feature provides PCI error information to
> > + * userspace for vfio-pci devices on s390. On s390, PCI error recovery
> > + * involves platform firmware and notification to operating systems is done
> > + * by architecture specific mechanism. Exposing this information to
> > + * userspace allows it to take appropriate actions to handle an
> > + * error on the device. The ioctl returns -ENOMSG if there are no pending
> > + * PCI errors.
> > + */
> > +
> > +struct vfio_device_feature_zpci_err {
> > +	__u32 feature_flags;		/* Indicate future features */
> > +	__u32 reserved1;
> > +	__u32 fh;			/* function handle */
> > +	__u32 fid;			/* function id */
> > +	__u32 ett		:  4;	/* expected table type */
> > +	__u32 mvn		: 12;	/* MSI vector number */
> > +	__u32 dmaas		:  8;	/* DMA address space */
> > +	__u32 reserved2		:  6;
> > +	__u32 q			:  1;	/* event qualifier */
> > +	__u32 rw		:  1;	/* read/write */
> There's a 4-byte hole here.
>
> > +	__u64 faddr;			/* failing address */
> > +	__u32 reserved3;
> > +	__u16 reserved4;
> > +	__u16 pec;			/* PCI event code */
> > +	__u8 reserved5[28];		/* Allow for future expansion */
> > +};
> > +
> > +#define VFIO_DEVICE_FEATURE_ZPCI_ERROR 13
> Based on the discussion with Omar and FMB reporting, I don't suppose
> this could also be copied to a user buffer as opaque data with size
> reported elsewhere, could it?  Thanks,
>
> Alex

We currently don't expose any PCI error data to userspace and so 
userspace has no way of knowing the size of the buffer. Unless we 
provide the size, i don't think we can copy the user buffer as opaque data.

Thanks

Farhan