vfio/pds: Refactor/simplify reset logic

The current logic for handling resets is more complicated than it needs
to be. The deferred_reset flag is used to indicate a reset is needed
and the deferred_reset_state is the requested, post-reset, state.

Also, the deferred_reset logic was added to vfio migration drivers to
prevent a circular locking dependency with respect to mm_lock and state
mutex. This is mainly because of the copy_to/from_user() functions(which
takes mm_lock) invoked under state mutex.

Remove all of the deferred reset logic and just pass the requested
next state to pds_vfio_reset() so it can be used for VMM and DSC
initiated resets.

This removes the need for pds_vfio_state_mutex_lock(), so remove that
and replace its use with a simple mutex_unlock().

Also, remove the reset_mutex as it's no longer needed since the
state_mutex can be the driver's primary protector.

Suggested-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Reviewed-by: Shannon Nelson <shannon.nelson@amd.com>
Signed-off-by: Brett Creeley <brett.creeley@amd.com>
Link: https://lore.kernel.org/r/20240308182149.22036-3-brett.creeley@amd.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/drivers/vfio/pci/pds/dirty.c b/drivers/vfio/pci/pds/dirty.c
index 8ddf4346fcd5..68e8f006dfdb 100644
--- a/drivers/vfio/pci/pds/dirty.c
+++ b/drivers/vfio/pci/pds/dirty.c
@@ -607,7 +607,7 @@ int pds_vfio_dma_logging_report(struct vfio_device *vdev, unsigned long iova,
 
 	mutex_lock(&pds_vfio->state_mutex);
 	err = pds_vfio_dirty_sync(pds_vfio, dirty, iova, length);
-	pds_vfio_state_mutex_unlock(pds_vfio);
+	mutex_unlock(&pds_vfio->state_mutex);
 
 	return err;
 }
@@ -624,7 +624,7 @@ int pds_vfio_dma_logging_start(struct vfio_device *vdev,
 	mutex_lock(&pds_vfio->state_mutex);
 	pds_vfio_send_host_vf_lm_status_cmd(pds_vfio, PDS_LM_STA_IN_PROGRESS);
 	err = pds_vfio_dirty_enable(pds_vfio, ranges, nnodes, page_size);
-	pds_vfio_state_mutex_unlock(pds_vfio);
+	mutex_unlock(&pds_vfio->state_mutex);
 
 	return err;
 }
@@ -637,7 +637,7 @@ int pds_vfio_dma_logging_stop(struct vfio_device *vdev)
 
 	mutex_lock(&pds_vfio->state_mutex);
 	pds_vfio_dirty_disable(pds_vfio, true);
-	pds_vfio_state_mutex_unlock(pds_vfio);
+	mutex_unlock(&pds_vfio->state_mutex);
 
 	return 0;
 }