Re: [PATCH v2] vfio/ap_ops: Add missed vfio_uninit_group_dev()

Tony Krowiak
2021-09-20T21:28:36Z

On 9/16/21 2:51 PM, Alex Williamson wrote:
> On Fri, 10 Sep 2021 20:06:30 -0300
> Jason Gunthorpe <jgg@nvidia.com> wrote:
>
>> Without this call an xarray entry is leaked when the vfio_ap device is
>> unprobed. It was missed when the below patch was rebased across the
>> dev_set patch.
>>
>> Fixes: eb0feefd4c02 ("vfio/ap_ops: Convert to use vfio_register_group_dev()")
>> Reviewed-by: Christoph Hellwig <hch@lst.de>
>> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
>> ---
>> drivers/s390/crypto/vfio_ap_ops.c | 2 ++
>> 1 file changed, 2 insertions(+)
> Hi Tony, Halil, Jason (H),
>
> Any acks for this one? Thanks,
>
> Alex

I installed this on a test system running the latest linux
code from our library and ran our test suite. I got the
following running a simple test case that assigns some
adapters and domains to a mediated device then
starts a guest using the mdev.

[Sep20 23:19] ======================================================
[  +0.000001] WARNING: possible circular locking dependency detected
[  +0.000002] 5.15.0-rc1-10318-gac08b1c68d1b-dirty #15 Not tainted
[  +0.000002] ------------------------------------------------------
[  +0.000001] nose2/1993 is trying to acquire lock:
[  +0.000002] 00000000cf2a5520 (&new_dev_set->lock){+.+.}-{3:3}, at:
vfio_uninit_group_dev+0x3c/0xf0 [vfio]
[  +0.000012]
but task is already holding lock:
[  +0.000001] 00000000c84424d8 (&matrix_dev->lock){+.+.}-{3:3}, at:
vfio_ap_mdev_remove+0x48/0xc8 [vfio_ap]
[  +0.000006]
which lock already depends on the new lock.

[  +0.000002]
the existing dependency chain (in reverse order) is:
[  +0.000001]
-> #1 (&matrix_dev->lock){+.+.}-{3:3}:
[  +0.000004]        __lock_acquire+0x64c/0xc40
[  +0.000005]        reacquire_held_locks+0x134/0x228
[  +0.000002]        __lock_release+0xc6/0x338
[  +0.000002]        lock_release+0x1b0/0x298
[  +0.000001]        __mutex_unlock_slowpath+0x3a/0x2d8
[  +0.000005]        vfio_ap_mdev_unset_kvm.part.0+0xa6/0xc0 [vfio_ap]
[  +0.000003]        vfio_device_fops_release+0x64/0xe8 [vfio]
[  +0.000003]        __fput+0xae/0x288
[  +0.000005]        task_work_run+0x76/0xc0
[  +0.000005]        do_exit+0x268/0x5c0
[  +0.000005]        do_group_exit+0x48/0xc0
[  +0.000050]        __s390x_sys_exit_group+0x2e/0x30
[  +0.000002]        __do_syscall+0x1c2/0x1f0
[  +0.000004]        system_call+0x78/0xa0
[  +0.000003]
-> #0 (&new_dev_set->lock){+.+.}-{3:3}:
[  +0.000004]        check_prev_add+0xe0/0xed8
[  +0.000002]        validate_chain+0x9ca/0xde8
[  +0.000001]        __lock_acquire+0x64c/0xc40
[  +0.000002]        lock_acquire.part.0+0xec/0x258
[  +0.000002]        lock_acquire+0xb0/0x200
[  +0.000001]        __mutex_lock+0xa2/0x8f8
[  +0.000002]        mutex_lock_nested+0x32/0x40
[  +0.000002]        vfio_uninit_group_dev+0x3c/0xf0 [vfio]
[  +0.000004]        vfio_ap_mdev_remove+0x90/0xc8 [vfio_ap]
[  +0.000002]        mdev_remove+0x32/0x58 [mdev]
[  +0.000004]        __device_release_driver+0x18a/0x238
[  +0.000005]        device_release_driver+0x40/0x50
[  +0.000002]        bus_remove_device+0x110/0x1a0
[  +0.000002]        device_del+0x19c/0x3e8
[  +0.000002]        mdev_device_remove_common+0x3c/0xb0 [mdev]
[  +0.000003]        mdev_device_remove+0xac/0x100 [mdev]
[  +0.000002]        remove_store+0x78/0x90 [mdev]
[  +0.000003]        kernfs_fop_write_iter+0x13e/0x1e0
[  +0.000004]        new_sync_write+0x100/0x190
[  +0.000003]        vfs_write+0x230/0x2e0
[  +0.000002]        ksys_write+0x6c/0xf8
[  +0.000002]        __do_syscall+0x1c2/0x1f0
[  +0.000002]        system_call+0x78/0xa0
[  +0.000002]
other info that might help us debug this:

[  +0.000002]  Possible unsafe locking scenario:

[  +0.000001]        CPU0                    CPU1
[  +0.000001]        ----                    ----
[  +0.000001]   lock(&matrix_dev->lock);
[  +0.000002] lock(&new_dev_set->lock);
[  +0.000002] lock(&matrix_dev->lock);
[  +0.000002]   lock(&new_dev_set->lock);
[  +0.000002]
*** DEADLOCK ***

[  +0.000001] 7 locks held by nose2/1993:
[  +0.000002]  #0: 00000000b373af00 (&f->f_pos_lock){+.+.}-{3:3}, at:
__fdget_pos+0x6a/0x80
[  +0.000007]  #1: 00000000978e4498 (sb_writers#4){.+.+}-{0:0}, at:
ksys_write+0x6c/0xf8
[  +0.000005]  #2: 00000000b4b89490 (&of->mutex){+.+.}-{3:3}, at:
kernfs_fop_write_iter+0x102/0x1e0
[  +0.000006]  #3: 00000000ca215210 (kn->active#215){++++}-{0:0}, at:
sysfs_remove_file_self+0x42/0x78
[  +0.000006]  #4: 00000000cb7d85b8 (&parent->unreg_sem){++++}-{3:3},
at: mdev_device_remove+0x9c/0x100 [mdev]
[  +0.000005]  #5: 00000000cb188990 (&dev->mutex){....}-{3:3}, at:
device_release_driver+0x32/0x50
[  +0.000006]  #6: 00000000c84424d8 (&matrix_dev->lock){+.+.}-{3:3}, at:
vfio_ap_mdev_remove+0x48/0xc8 [vfio_ap]
[  +0.000005]
stack backtrace:
[  +0.000002] CPU: 6 PID: 1993 Comm: nose2 Not tainted
5.15.0-rc1-10318-gac08b1c68d1b-dirty #15
[  +0.000003] Hardware name: IBM 8561 T01 701 (LPAR)
[  +0.000002] Call Trace:
[  +0.000001]  [<0000000328775056>] dump_stack_lvl+0x8e/0xc8
[  +0.000003]  [<0000000327b4b648>] check_noncircular+0x168/0x188
[  +0.000003]  [<0000000327b4c708>] check_prev_add+0xe0/0xed8
[  +0.000002]  [<0000000327b4deca>] validate_chain+0x9ca/0xde8
[  +0.000002]  [<0000000327b50ec4>] __lock_acquire+0x64c/0xc40
[  +0.000002]  [<0000000327b4facc>] lock_acquire.part.0+0xec/0x258
[  +0.000002]  [<0000000327b4fce8>] lock_acquire+0xb0/0x200
[  +0.000002]  [<00000003287839d2>] __mutex_lock+0xa2/0x8f8
[  +0.000002]  [<000000032878425a>] mutex_lock_nested+0x32/0x40
[  +0.000002]  [<000003ff801c3ce4>] vfio_uninit_group_dev+0x3c/0xf0 [vfio]
[  +0.000004]  [<000003ff805e0000>] vfio_ap_mdev_remove+0x90/0xc8 [vfio_ap]
[  +0.000003]  [<000003ff802339fa>] mdev_remove+0x32/0x58 [mdev]
[  +0.000003]  [<00000003283e9c92>] __device_release_driver+0x18a/0x238
[  +0.000003]  [<00000003283e9d80>] device_release_driver+0x40/0x50
[  +0.000003]  [<00000003283e8e28>] bus_remove_device+0x110/0x1a0
[  +0.000002]  [<00000003283e2cb4>] device_del+0x19c/0x3e8
[  +0.000002]  [<000003ff8023270c>] mdev_device_remove_common+0x3c/0xb0
[mdev]
[  +0.000003]  [<000003ff80232fcc>] mdev_device_remove+0xac/0x100 [mdev]
[  +0.000003]  [<000003ff80233220>] remove_store+0x78/0x90 [mdev]
[  +0.000003]  [<0000000327eefaae>] kernfs_fop_write_iter+0x13e/0x1e0
[  +0.000003]  [<0000000327dfa160>] new_sync_write+0x100/0x190
[  +0.000002]  [<0000000327dfd038>] vfs_write+0x230/0x2e0
[  +0.000003]  [<0000000327dfd354>] ksys_write+0x6c/0xf8
[  +0.000002]  [<00000003287787b2>] __do_syscall+0x1c2/0x1f0
[  +0.000002]  [<000000032878b178>] system_call+0x78/0xa0
[  +0.000003] INFO: lockdep is turned off.