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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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