[Intel-gfx] [PATCH v2 00/10] Introduce new methods for verifying ownership in vfio PCI hot reset

[Jiang, Yanting]

> 
> VFIO_DEVICE_PCI_HOT_RESET requires user to pass an array of group fds to
> prove that it owns all devices affected by resetting the calling device. This series
> introduces several extensions to allow the ownership check better aligned with
> iommufd and coming vfio device cdev support.
> 
> First, resetting an unopened device is always safe given nobody is using it. So
> relax the check to allow such devices not covered by group fd array. [1]
> 
> When iommufd is used we can simply verify that all affected devices are bound
> to a same iommufd then no need for the user to provide extra fd information.
> This is enabled by the user passing a zero-length fd array and moving forward
> this should be the preferred way for hot reset. [2]
> 
> However the iommufd method has difficulty working with noiommu devices
> since those devices don't have a valid iommufd, unless the noiommu device is in
> a singleton dev_set hence no ownership check is required. [3]
> 
> For noiommu backward compatibility a 3rd method is introduced by allowing the
> user to pass an array of device fds to prove ownership. [4]
> 
> As suggested by Jason [5], we have this series to introduce the above stuffs to
> the vfio PCI hot reset. Per the dicussion in [6], this series also adds a new _INFO
> ioctl to get hot reset scope for given device.
> 
Tested NIC passthrough on Intel platform.
Result looks good hence, 
Tested by: Jiang, Yanting <yanting.jiang at intel.com>

Thanks,
Yanting