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

[Xu, Terrence]

> -----Original Message-----
> From: Liu, Yi L <yi.l.liu at intel.com>
> Sent: Monday, March 27, 2023 5:35 PM
> 
> 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.
> 
> [1] https://lore.kernel.org/kvm/Y%2FdobS6gdSkxnPH7@nvidia.com/
> [2] https://lore.kernel.org/kvm/Y%2FZOOClu8nXy2toX@nvidia.com/#t
> [3] https://lore.kernel.org/kvm/ZACX+Np%2FIY7ygqL5@nvidia.com/
> [4]
> https://lore.kernel.org/kvm/DS0PR11MB7529BE88460582BD599DC1F7C3B19
> @DS0PR11MB7529.namprd11.prod.outlook.com/#t
> [5] https://lore.kernel.org/kvm/ZAcvzvhkt9QhCmdi@nvidia.com/
> [6] https://lore.kernel.org/kvm/ZBoYgNq60eDpV9Un@nvidia.com/
> 
> Change log:
> 
> v2:
>  - Split the patch 03 of v1 to be 03, 04 and 05 of v2 (Jaon)
>  - Add r-b from Kevin and Jason
>  - Add patch 10 to introduce a new _INFO ioctl for the usage of device
>    fd passing usage in cdev path (Jason, Alex)
> 
> v1: https://lore.kernel.org/kvm/20230316124156.12064-1-yi.l.liu@intel.com/
> 
> Regards,
> 	Yi Liu
> 
> Yi Liu (10):
>   vfio/pci: Update comment around group_fd get in
>     vfio_pci_ioctl_pci_hot_reset()
>   vfio/pci: Only check ownership of opened devices in hot reset
>   vfio/pci: Move the existing hot reset logic to be a helper
>   vfio-iommufd: Add helper to retrieve iommufd_ctx and devid for
>     vfio_device
>   vfio/pci: Allow passing zero-length fd array in
>     VFIO_DEVICE_PCI_HOT_RESET
>   vfio: Refine vfio file kAPIs for vfio PCI hot reset
>   vfio: Accpet device file from vfio PCI hot reset path
>   vfio/pci: Renaming for accepting device fd in hot reset path
>   vfio/pci: Accept device fd in VFIO_DEVICE_PCI_HOT_RESET ioctl
>   vfio/pci: Add VFIO_DEVICE_GET_PCI_HOT_RESET_GROUP_INFO
> 
>  drivers/iommu/iommufd/device.c   |  12 ++
>  drivers/vfio/group.c             |  32 ++--
>  drivers/vfio/iommufd.c           |  16 ++
>  drivers/vfio/pci/vfio_pci_core.c | 244 ++++++++++++++++++++++++-------
>  drivers/vfio/vfio.h              |   2 +
>  drivers/vfio/vfio_main.c         |  44 ++++++
>  include/linux/iommufd.h          |   3 +
>  include/linux/vfio.h             |  14 ++
>  include/uapi/linux/vfio.h        |  65 +++++++-
>  9 files changed, 364 insertions(+), 68 deletions(-)
> 
> --
> 2.34.1

Verified this series by "Intel GVT-g GPU device mediated passthrough".
Passed VFIO legacy mode / compat mode / cdev mode basic functionality and GPU force reset test.

Tested-by: Terrence Xu <terrence.xu at intel.com>