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    SubjectRE: [PATCHv2 00/10] vfio/mdev: Improve vfio/mdev core module
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    > -----Original Message-----
    > From: Alex Williamson <alex.williamson@redhat.com>
    > Sent: Monday, May 6, 2019 5:03 PM
    > To: Parav Pandit <parav@mellanox.com>
    > Cc: kvm@vger.kernel.org; linux-kernel@vger.kernel.org;
    > kwankhede@nvidia.com; cjia@nvidia.com
    > Subject: Re: [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,
    >
    Ok. Great.
    Yes, these are important for us to make use of mdev.
    We should address them in 5.2 window.
    I will look for any comments this week and address them as required.

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