[Intel-gfx] [PATCH v7 8/9] vfio/pci: Extend VFIO_DEVICE_GET_PCI_HOT_RESET_INFO for vfio device cdev

[Alex Williamson]

On Tue, 13 Jun 2023 12:50:43 +0000
"Liu, Yi L" <yi.l.liu at intel.com> wrote:

> > From: Jason Gunthorpe <jgg at nvidia.com>
> > Sent: Tuesday, June 13, 2023 7:47 PM
> > 
> > On Fri, Jun 02, 2023 at 05:15:14AM -0700, Yi Liu wrote:  
> > > +/*
> > > + * Return devid for a device which is affected by hot-reset.
> > > + * - valid devid > 0 for the device that is bound to the input
> > > + *   iommufd_ctx.
> > > + * - devid == VFIO_PCI_DEVID_OWNED for the device that has not
> > > + *   been bound to any iommufd_ctx but other device within its
> > > + *   group has been bound to the input iommufd_ctx.
> > > + * - devid == VFIO_PCI_DEVID_NOT_OWNED for others. e.g. device
> > > + *   is bound to other iommufd_ctx etc.
> > > + */
> > > +int vfio_iommufd_device_hot_reset_devid(struct vfio_device *vdev,
> > > +					struct iommufd_ctx *ictx)
> > > +{
> > > +	struct iommu_group *group;
> > > +	int devid;
> > > +
> > > +	if (vfio_iommufd_device_ictx(vdev) == ictx)
> > > +		return vfio_iommufd_device_id(vdev);
> > > +
> > > +	group = iommu_group_get(vdev->dev);
> > > +	if (!group)
> > > +		return VFIO_PCI_DEVID_NOT_OWNED;
> > > +
> > > +	if (iommufd_ctx_has_group(ictx, group))
> > > +		devid = VFIO_PCI_DEVID_OWNED;
> > > +	else
> > > +		devid = VFIO_PCI_DEVID_NOT_OWNED;
> > > +
> > > +	iommu_group_put(group);
> > > +
> > > +	return devid;
> > > +}
> > > +EXPORT_SYMBOL_GPL(vfio_iommufd_device_hot_reset_devid);  
> > 
> > This function really should not be in the core iommufd.c file - it is
> > a purely vfio-pci function - why did you have to place it here?  
> 
> Put it here can avoid calling iommufd_ctx_has_group() in vfio-pci,
> which requires to import IOMMUFD_NS. If this reason is not so
> strong I can move it back to vfio-pci code.

The PCI-isms here are the name of the function and the return value,
otherwise this is simply a "give me the devid for this device in this
context".  The function name is trivial to change and we can define the
internal errno usage such that the vfio-pci-core code can interpret the
correct uAPI value.  For example, -EXDEV ("Cross-device link") could
maybe be interpreted as owned and any other errno is not-owned, -ENODEV
maybe being the default.

Errno values are often contentious, are there other suggestions?
Thanks,

Alex