As we would like to use mdev subsystem for wider use case as discussed in [1], [2] apart from an offline discussion. This use case is also discussed with wider forum in [4] in track 'Lightweight NIC HW functions for container offload use cases'. This series is prep-work and improves vfio/mdev module in following ways. Patch-1 Improves the mdev create/remove sequence to match Linux bus, device model Patch-2 Avoid recreating remove file on stale device to eliminate call trace Patch-3 Fix race conditions of create/remove with parent removal. This is improved version than using srcu as srcu can take seconds to minutes. This series is tested using (a) mtty with VM using vfio_mdev driver for positive tests and device removal while device in use by VM using vfio_mdev driver. (b) mlx5 core driver using RFC patches [3] and internal patches. Internal patches are large and cannot be combined with this prep-work patches. It will posted once prep-work completes. [1] https://www.spinics.net/lists/netdev/msg556978.html [2] https://lkml.org/lkml/2019/3/7/696 [3] https://lkml.org/lkml/2019/3/8/819 [4] https://netdevconf.org/0x13/session.html?workshop-hardware-offload --- Changelog: --- v5->v6: - Fixed mdev leak on fail to acquire semaphore - Corrected access to accessed - Avoided using ret and directly checking try_lock result v4->v5: - Addressed comments from Alex Williamson - Added comment around mdev_device_remove_common() - Added lockdep assert to catch any missing lock - Corrected 'system' to 'sequence' in 2nd patch commit log - Refactored mdev_device_remove_cb() to remove unused parent - Added Cornelia's Reviewed-by signature to already reviewed patches 1, 2. v3->v4: - Addressed comments from Cornelia for unbalanced mutex_unlock - Correct typo of subsquent to subsequent in patch-1 commit log - Instead of using refcount and completion, using rwsem to synchronize between mdev creation/deletion and parent unregistration v2->v3: - Addressed comment from Cornelia - Corrected several errors in commit log, updated commit log - Dropped already merged 7 patches v1->v2: - Addressed comments from Alex - Rebased - Inserted the device checking loop in Patch-6 as original code - Added patch 7 to 10 - Added fixes for race condition in create/remove with parent removal Patch-10 uses simplified refcount and completion, instead of srcu which might take seconds to minutes on busy system. - Added fix for device create/remove sequence to match Linux device, bus model v0->v1: - Dropped device placement on bus sequence patch for this series - Addressed below comments from Alex, Kirti, Maxim. - Added Review-by tag for already reviewed patches. - Dropped incorrect patch of put_device(). - Corrected Fixes commit tag for sysfs remove sequence fix - Split last 8th patch to smaller refactor and fixes patch - Following coding style commenting format - Fixed accidental delete of mutex_lock in mdev_unregister_device - Renamed remove helped to mdev_device_remove_common(). - Rebased for uuid/guid change Parav Pandit (3): vfio/mdev: Improve the create/remove sequence vfio/mdev: Avoid creating sysfs remove file on stale device removal vfio/mdev: Synchronize device create/remove with parent removal drivers/vfio/mdev/mdev_core.c | 135 +++++++++++++++---------------- drivers/vfio/mdev/mdev_private.h | 4 +- drivers/vfio/mdev/mdev_sysfs.c | 6 +- 3 files changed, 68 insertions(+), 77 deletions(-) -- 2.19.2
