[Intel-gfx] [PATCH v3 05/12] vfio/pci: Allow passing zero-length fd array in VFIO_DEVICE_PCI_HOT_RESET

[Liu, Yi L]

> From: Liu, Yi L <yi.l.liu at intel.com>
> Sent: Wednesday, April 5, 2023 3:55 PM
 
> >
> > Therefore, I think as written, the singleton dev_set hot-reset is
> > enabled for iommufd and (unintentionally?) for the group path, while
> > also negating a requirement for a group fd or that a provided group fd
> > actually matches the device in this latter case.  The null-array
> > approach is not however extended to groups for more general use.
> > Additionally, limiting no-iommu hot-reset to singleton dev_sets
> > provides only a marginal functional difference vs VFIO_DEVICE_RESET.
> 
> I think the singletion dev_set hot-reset is for iommufd (or more accurately
> for the noiommu case in cdev path).

but actually, singleton dev_set hot-reset can work for group path as well.
Based on this, I'm also wondering do we really want to have singleton dev_set
hot-reset only for cdev noiommu case? or we allow it generally or just
don't support it as it is equivalent with VFIO_DEVICE_RESET?

If we don't support singletion dev_set hot-reset, noiommu devices in cdev
path shall fail the hot-reset if empty-fd array is provided. But we may just
document that empty-fd array does not work for noiommu. User should
use the device fd array.

Regards,
Yi Liu