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, 5 insertions, 22 deletions

diff --git a/drivers/vfio/pci/pds/pci_drv.c b/drivers/vfio/pci/pds/pci_drv.c
index a34dda516629..16e93b11ab1b 100644
--- a/drivers/vfio/pci/pds/pci_drv.c
+++ b/drivers/vfio/pci/pds/pci_drv.c
@@ -21,16 +21,13 @@
 
 static void pds_vfio_recovery(struct pds_vfio_pci_device *pds_vfio)
 {
-	bool deferred_reset_needed = false;
-
 	/*
 	 * Documentation states that the kernel migration driver must not
 	 * generate asynchronous device state transitions outside of
 	 * manipulation by the user or the VFIO_DEVICE_RESET ioctl.
 	 *
 	 * Since recovery is an asynchronous event received from the device,
-	 * initiate a deferred reset. Issue a deferred reset in the following
-	 * situations:
+	 * initiate a reset in the following situations:
 	 *   1. Migration is in progress, which will cause the next step of
 	 *	the migration to fail.
 	 *   2. If the device is in a state that will be set to
@@ -42,24 +39,8 @@ static void pds_vfio_recovery(struct pds_vfio_pci_device *pds_vfio)
 	     pds_vfio->state != VFIO_DEVICE_STATE_ERROR) ||
 	    (pds_vfio->state == VFIO_DEVICE_STATE_RUNNING &&
 	     pds_vfio_dirty_is_enabled(pds_vfio)))
-		deferred_reset_needed = true;
+		pds_vfio_reset(pds_vfio, VFIO_DEVICE_STATE_ERROR);
 	mutex_unlock(&pds_vfio->state_mutex);
-
-	/*
-	 * On the next user initiated state transition, the device will
-	 * transition to the VFIO_DEVICE_STATE_ERROR. At this point it's the user's
-	 * responsibility to reset the device.
-	 *
-	 * If a VFIO_DEVICE_RESET is requested post recovery and before the next
-	 * state transition, then the deferred reset state will be set to
-	 * VFIO_DEVICE_STATE_RUNNING.
-	 */
-	if (deferred_reset_needed) {
-		mutex_lock(&pds_vfio->reset_mutex);
-		pds_vfio->deferred_reset = true;
-		pds_vfio->deferred_reset_state = VFIO_DEVICE_STATE_ERROR;
-		mutex_unlock(&pds_vfio->reset_mutex);
-	}
 }
 
 static int pds_vfio_pci_notify_handler(struct notifier_block *nb,
@@ -185,7 +166,9 @@ static void pds_vfio_pci_aer_reset_done(struct pci_dev *pdev)
 {
 	struct pds_vfio_pci_device *pds_vfio = pds_vfio_pci_drvdata(pdev);
 
-	pds_vfio_reset(pds_vfio);
+	mutex_lock(&pds_vfio->state_mutex);
+	pds_vfio_reset(pds_vfio, VFIO_DEVICE_STATE_RUNNING);
+	mutex_unlock(&pds_vfio->state_mutex);
 }
 
 static const struct pci_error_handlers pds_vfio_pci_err_handlers = {