linux-toradex.git/drivers/vfio/vfio.c, branch v5.0

vfio: use match_string() helper

2018-06-08T16:24:33+00:00

match_string() returns the index of an array for a matching string,
which can be used intead of open coded variant.

Cc: Alex Williamson 
Cc: kvm@vger.kernel.org
Signed-off-by: Yisheng Xie 
Reviewed-by: Andy Shevchenko 
Signed-off-by: Alex Williamson

vfio: Simplify capability helper

2017-12-20T16:53:54+00:00

The vfio_info_add_capability() helper requires the caller to pass a
capability ID, which it then uses to fill in header fields, assuming
hard coded versions.  This makes for an awkward and rigid interface.
The only thing we want this helper to do is allocate sufficient
space in the caps buffer and chain this capability into the list.
Reduce it to that simple task.

Reviewed-by: Alexey Kardashevskiy 
Acked-by: Zhenyu Wang 
Reviewed-by: Kirti Wankhede 
Reviewed-by: Peter Xu 
Reviewed-by: Eric Auger 
Signed-off-by: Alex Williamson

locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns to READ_ONCE()/WRITE_ONCE()

2017-10-25T09:01:08+00:00

Please do not apply this to mainline directly, instead please re-run the
coccinelle script shown below and apply its output.

For several reasons, it is desirable to use {READ,WRITE}_ONCE() in
preference to ACCESS_ONCE(), and new code is expected to use one of the
former. So far, there's been no reason to change most existing uses of
ACCESS_ONCE(), as these aren't harmful, and changing them results in
churn.

However, for some features, the read/write distinction is critical to
correct operation. To distinguish these cases, separate read/write
accessors must be used. This patch migrates (most) remaining
ACCESS_ONCE() instances to {READ,WRITE}_ONCE(), using the following
coccinelle script:

----
// Convert trivial ACCESS_ONCE() uses to equivalent READ_ONCE() and
// WRITE_ONCE()

// $ make coccicheck COCCI=/home/mark/once.cocci SPFLAGS="--include-headers" MODE=patch

virtual patch

@ depends on patch @
expression E1, E2;
@@

- ACCESS_ONCE(E1) = E2
+ WRITE_ONCE(E1, E2)

@ depends on patch @
expression E;
@@

- ACCESS_ONCE(E)
+ READ_ONCE(E)
----

Signed-off-by: Mark Rutland 
Signed-off-by: Paul E. McKenney 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: davem@davemloft.net
Cc: linux-arch@vger.kernel.org
Cc: mpe@ellerman.id.au
Cc: shuah@kernel.org
Cc: snitzer@redhat.com
Cc: thor.thayer@linux.intel.com
Cc: tj@kernel.org
Cc: viro@zeniv.linux.org.uk
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1508792849-3115-19-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar

vfio: Stall vfio_del_group_dev() for container group detach

2017-08-30T20:02:16+00:00

When the user unbinds the last device of a group from a vfio bus
driver, the devices within that group should be available for other
purposes.  We currently have a race that makes this generally, but
not always true.  The device can be unbound from the vfio bus driver,
but remaining IOMMU context of the group attached to the container
can result in errors as the next driver configures DMA for the device.

Wait for the group to be detached from the IOMMU backend before
allowing the bus driver remove callback to complete.

Signed-off-by: Alex Williamson

vfio: fix noiommu vfio_iommu_group_get reference count

2017-08-30T20:00:47+00:00

In vfio_iommu_group_get() we want to increase the reference
count of the iommu group.

In noiommu case, the group does not exist and is allocated.
iommu_group_add_device() increases the group ref count. However we
then call iommu_group_put() which decrements it.

This leads to a "refcount_t: underflow WARN_ON".

Only decrement the ref count in case of iommu_group_add_device
failure.

Signed-off-by: Eric Auger 
Signed-off-by: Alex Williamson

vfio: Remove unnecessary uses of vfio_container.group_lock

2017-07-07T21:37:38+00:00

The original intent of vfio_container.group_lock is to protect
vfio_container.group_list, however over time it's become a crutch to
prevent changes in container composition any time we call into the
iommu driver backend.  This introduces problems when we start to have
more complex interactions, for example when a user's DMA unmap request
triggers a notification to an mdev vendor driver, who responds by
attempting to unpin mappings within that request, re-entering the
iommu backend.  We incorrectly assume that the use of read-locks here
allow for this nested locking behavior, but a poorly timed write-lock
could in fact trigger a deadlock.

The current use of group_lock seems to fall into the trap of locking
code, not data.  Correct that by removing uses of group_lock that are
not directly related to group_list.  Note that the vfio type1 iommu
backend has its own mutex, vfio_iommu.lock, which it uses to protect
itself for each of these interfaces anyway.  The group_lock appears to
be a redundancy for these interfaces and type1 even goes so far as to
release its mutex to allow for exactly the re-entrant code path above.

Reported-by: Chuanxiao Dong 
Signed-off-by: Alex Williamson 
Acked-by: Alexey Kardashevskiy 
Cc: stable@vger.kernel.org # v4.10+

vfio: New external user group/file match

2017-06-28T19:50:05+00:00

At the point where the kvm-vfio pseudo device wants to release its
vfio group reference, we can't always acquire a new reference to make
that happen.  The group can be in a state where we wouldn't allow a
new reference to be added.  This new helper function allows a caller
to match a file to a group to facilitate this.  Given a file and
group, report if they match.  Thus the caller needs to already have a
group reference to match to the file.  This allows the deletion of a
group without acquiring a new reference.

Signed-off-by: Alex Williamson 
Reviewed-by: Eric Auger 
Reviewed-by: Paolo Bonzini 
Tested-by: Eric Auger 
Cc: stable@vger.kernel.org

vfio: Fix group release deadlock

2017-06-28T19:49:38+00:00

If vfio_iommu_group_notifier() acquires a group reference and that
reference becomes the last reference to the group, then vfio_group_put
introduces a deadlock code path where we're trying to unregister from
the iommu notifier chain from within a callout of that chain.  Use a
work_struct to release this reference asynchronously.

Signed-off-by: Alex Williamson 
Reviewed-by: Eric Auger 
Tested-by: Eric Auger 
Cc: stable@vger.kernel.org

vfio: Use ERR_CAST() instead of open coding it

2017-06-13T15:24:21+00:00

It's a small cleanup to use ERR_CAST() here.

Signed-off-by: Dan Carpenter 
Signed-off-by: Alex Williamson

vfio: Rework group release notifier warning

2017-03-21T19:19:09+00:00

The intent of the original warning is make sure that the mdev vendor
driver has removed any group notifiers at the point where the group
is closed by the user.  Theoretically this would be through an
orderly shutdown where any devices are release prior to the group
release.  We can't always count on an orderly shutdown, the user can
close the group before the notifier can be removed or the user task
might be killed.  We'd like to add this sanity test when the group is
idle and the only references are from the devices within the group
themselves, but we don't have a good way to do that.  Instead check
both when the group itself is removed and when the group is opened.
A bit later than we'd prefer, but better than the current over
aggressive approach.

Fixes: ccd46dbae77d ("vfio: support notifier chain in vfio_group")
Signed-off-by: Alex Williamson 
Cc:  # v4.10
Cc: Jike Song