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    SubjectRe: [PATCHv2 00/10] vfio/mdev: Improve vfio/mdev core module
    On Tue, 30 Apr 2019 17:49:27 -0500
    Parav Pandit <parav@mellanox.com> wrote:

    > 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 Fixes releasing parent dev reference during error unwinding
    > mdev parent registration.
    > Patch-2 Simplifies mdev device for unused kref.
    > Patch-3 Drops redundant extern prefix of exported symbols.
    > Patch-4 Returns right error code from vendor driver.
    > Patch-5 Fixes to use right sysfs remove sequence.
    > Patch-6 Fixes removing all child devices if one of them fails.
    > Patch-7 Remove unnecessary inline
    > Patch-8 Improve the mdev create/remove sequence to match Linux
    > bus, device model
    > Patch-9 Avoid recreating remove file on stale device to
    > eliminate call trace
    > Patch-10 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:
    > ---
    > 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 (10):
    > vfio/mdev: Avoid release parent reference during error path
    > vfio/mdev: Removed unused kref
    > vfio/mdev: Drop redundant extern for exported symbols
    > vfio/mdev: Avoid masking error code to EBUSY
    > vfio/mdev: Follow correct remove sequence
    > vfio/mdev: Fix aborting mdev child device removal if one fails
    > vfio/mdev: Avoid inline get and put parent helpers
    > 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 | 162 +++++++++++++------------------
    > drivers/vfio/mdev/mdev_private.h | 9 +-
    > drivers/vfio/mdev/mdev_sysfs.c | 8 +-
    > include/linux/mdev.h | 21 ++--
    > 4 files changed, 89 insertions(+), 111 deletions(-)
    >

    Hi Parav,

    I applied 1-7 to the vfio next branch for v5.2 since these are mostly
    previously reviewed or trivial. I'm not ruling out the rest for v5.2
    as bug fixes yet, but they require a bit more to digest and hopefully
    we'll get some feedback from others as well. Thanks,

    Alex

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