Existing VFIO provides group-centric user APIs for userspace. Userspace opens the /dev/vfio/$group_id first before getting device fd and hence getting access to device. This is not the desired model for iommufd. Per the conclusion of community discussion[1], iommufd provides device-centric kAPIs and requires its consumer (like VFIO) to be device-centric user APIs. Such user APIs are used to associate device with iommufd and also the I/O address spaces managed by the iommufd. This series first introduces a per device file structure to be prepared for further enhancement and refactors the kvm-vfio code to be prepared for accepting device file from userspace. Then refactors the vfio to be able to handle iommufd binding. This refactor includes the mechanism of blocking device access before iommufd bind, making the device_open exclusive. between the group path and the cdev path. Eventually, adds the cdev support for vfio device, and makes group infrastructure optional as it is not needed when vfio device cdev is compiled. This is also a prerequisite for iommu nesting for vfio device[2]. The complete code can be found in below branch, simple test done with the legacy group path and the cdev path. Draft QEMU branch can be found at[3] https://github.com/yiliu1765/iommufd/tree/vfio_device_cdev_v5 (config CONFIG_IOMMUFD=y CONFIG_VFIO_DEVICE_CDEV=y) base-commit: 63777bd2daa3625da6eada88bd9081f047664dad [1] https://lore.kernel.org/kvm/BN9PR11MB5433B1E4AE5B0480369F97178C189@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ [2] https://lore.kernel.org/linux-iommu/20230209043153.14964-1-yi.l.liu@xxxxxxxxx/ [3] https://github.com/yiliu1765/qemu/tree/iommufd_rfcv3 (it is based on Eric's QEMU iommufd rfcv3 (https://lore.kernel.org/kvm/20230131205305.2726330-1-eric.auger@xxxxxxxxxx/) plus two commits to align with vfio_device_cdev v3/v4/v5) Change log: v5: - Add r-b from Kevin on patch 08, 13, 14, 15 and 17. - Rename patch 02 to limit the change for KVM facing kAPIs. The vfio pci hot reset path only accepts group file until patch 09. (Kevin) - Update comment around smp_load_acquire(&df->access_granted) (Yan) - Adopt Jason's suggestion on the vfio pci hot reset path, passing zero-length fd array to indicate using bound iommufd_ctx as ownership check. (Jason, Kevin) - Direct read df->access_granted value in vfio_device_cdev_close() (Kevin, Yan, Jason) - Wrap the iommufd get/put into a helper to refine the error path of vfio_device_ioctl_bind_iommufd(). (Yan) v4: https://lore.kernel.org/kvm/20230221034812.138051-1-yi.l.liu@xxxxxxxxx/ - Add r-b from Kevin on patch 09/10 - Add a line in devices/vfio.rst to emphasize user should add group/device to KVM prior to invoke open_device op which may be called in the VFIO_GROUP_GET_DEVICE_FD or VFIO_DEVICE_BIND_IOMMUFD ioctl. - Modify VFIO_GROUP/VFIO_DEVICE_CDEV Kconfig dependency (Alex) - Select VFIO_GROUP for SPAPR (Jason) - Check device fully-opened in PCI hotreset path for device fd (Jason) - Set df->access_granted in the caller of vfio_device_open() since the caller may fail in other operations, but df->access_granted does not allow a true to false change. So it should be set only when the open path is really done successfully. (Yan, Kevin) - Fix missing iommufd_ctx_put() in the cdev path (Yan) - Fix an issue found in testing exclusion between group and cdev path. vfio_device_cdev_close() should check df->access_granted before heading to other operations. - Update vfio.rst for iommufd/cdev v3: https://lore.kernel.org/kvm/20230213151348.56451-1-yi.l.liu@xxxxxxxxx/ - Add r-b from Kevin on patch 03, 06, 07, 08. - Refine the group and cdev path exclusion. Remove vfio_device:single_open; add vfio_group::cdev_device_open_cnt to achieve exlucsion between group path and cdev path (Kevin, Jason) - Fix a bug in the error handling path (Yan Zhao) - Address misc remarks from Kevin v2: https://lore.kernel.org/kvm/20230206090532.95598-1-yi.l.liu@xxxxxxxxx/ - Add r-b from Kevin and Eric on patch 01 02 04. - "Split kvm/vfio: Provide struct kvm_device_ops::release() insted of ::destroy()" from this series and got applied. (Alex, Kevin, Jason, Mathhew) - Add kvm_ref_lock to protect vfio_device_file->kvm instead of reusing dev_set->lock as dead-lock is observed with vfio-ap which would try to acquire kvm_lock. This is opposite lock order with kvm_device_release() which holds kvm_lock first and then hold dev_set->lock. (Kevin) - Use a separate ioctl for detaching IOAS. (Alex) - Rename vfio_device_file::single_open to be is_cdev_device (Kevin, Alex) - Move the vfio device cdev code into device_cdev.c and add a VFIO_DEVICE_CDEV kconfig for it. (Kevin, Jason) v1: https://lore.kernel.org/kvm/20230117134942.101112-1-yi.l.liu@xxxxxxxxx/ - Fix the circular refcount between kvm struct and device file reference. (JasonG) - Address comments from KevinT - Remained the ioctl for detach, needs to Alex's taste (https://lore.kernel.org/kvm/BN9PR11MB5276BE9F4B0613EE859317028CFF9@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/) rfc: https://lore.kernel.org/kvm/20221219084718.9342-1-yi.l.liu@xxxxxxxxx/ Thanks, Yi Liu Yi Liu (19): vfio: Allocate per device file structure vfio: Refine vfio file kAPIs for KVM vfio: Accept vfio device file in the KVM facing kAPI kvm/vfio: Rename kvm_vfio_group to prepare for accepting vfio device fd kvm/vfio: Accept vfio device file from userspace vfio: Pass struct vfio_device_file * to vfio_device_open/close() vfio: Block device access via device fd until device is opened vfio/pci: Update comment around group_fd get in vfio_pci_ioctl_pci_hot_reset() vfio/pci: Allow passing zero-length fd array in VFIO_DEVICE_PCI_HOT_RESET vfio: Add infrastructure for bind_iommufd from userspace vfio-iommufd: Add detach_ioas support for physical VFIO devices vfio-iommufd: Add detach_ioas for emulated VFIO devices vfio: Add cdev_device_open_cnt to vfio_group vfio: Make vfio_device_open() single open for device cdev path vfio: Add cdev for vfio_device vfio: Add VFIO_DEVICE_BIND_IOMMUFD vfio: Add VFIO_DEVICE_AT[DE]TACH_IOMMUFD_PT vfio: Compile group optionally docs: vfio: Add vfio device cdev description Documentation/driver-api/vfio.rst | 133 +++++++- Documentation/virt/kvm/devices/vfio.rst | 52 ++-- drivers/gpu/drm/i915/gvt/kvmgt.c | 1 + drivers/s390/cio/vfio_ccw_ops.c | 1 + drivers/s390/crypto/vfio_ap_ops.c | 1 + drivers/vfio/Kconfig | 26 ++ drivers/vfio/Makefile | 3 +- drivers/vfio/device_cdev.c | 285 ++++++++++++++++++ drivers/vfio/fsl-mc/vfio_fsl_mc.c | 1 + drivers/vfio/group.c | 139 ++++++--- drivers/vfio/iommufd.c | 59 +++- .../vfio/pci/hisilicon/hisi_acc_vfio_pci.c | 2 + drivers/vfio/pci/mlx5/main.c | 1 + drivers/vfio/pci/vfio_pci.c | 1 + drivers/vfio/pci/vfio_pci_core.c | 116 +++++-- drivers/vfio/platform/vfio_amba.c | 1 + drivers/vfio/platform/vfio_platform.c | 1 + drivers/vfio/vfio.h | 192 +++++++++++- drivers/vfio/vfio_main.c | 244 +++++++++++++-- include/linux/iommufd.h | 6 + include/linux/vfio.h | 40 ++- include/uapi/linux/kvm.h | 16 +- include/uapi/linux/vfio.h | 102 +++++++ virt/kvm/vfio.c | 141 ++++----- 24 files changed, 1348 insertions(+), 216 deletions(-) create mode 100644 drivers/vfio/device_cdev.c -- 2.34.1
