[RFC 2/7] s390/vfio-ap: circumvent filtering for adapters/domains not in host config

[Tony Krowiak <akrowiak@linux.ibm.com>]

While filtering the mdev matrix, it doesn't make sense - and will have
unexpected results - to filter an APID from the matrix if the APID or one
of the associated APQIs is not in the host's AP configuration. There are
two reasons for this:

1. An adapter or domain that is not in the host's AP configuration can be
   assigned to the matrix; this is known as over-provisioning. Queue
   devices, however, are only created for adapters and domains in the
   host's AP configuration, so there will be no queues associated with an
   over-provisioned adapter or domain to filter.

2. The adapter or domain may have been externally removed from the host's
   configuration via an SE or HMC attached to a DPM enabled LPAR. In this
   case, the vfio_ap device driver would have been notified by the AP bus
   via the on_config_changed callback and the adapter or domain would
   have already been filtered.

Let's bypass the filtering of an APID if an adapter or domain assigned to
the mdev matrix is not in the host's AP configuration.

Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
Fixes: 48cae940c31d ("s390/vfio-ap: refresh guest's APCB by filtering AP resources assigned to mdev")
Cc: <stable@vger.kernel.org>
---
 drivers/s390/crypto/vfio_ap_ops.c | 32 +++++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index e5490640e19c..4e40e226ce62 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -692,17 +692,37 @@ static bool vfio_ap_mdev_filter_matrix(struct ap_matrix_mdev *matrix_mdev)
 		   (unsigned long *)matrix_dev->info.aqm, AP_DOMAINS);
 
 	for_each_set_bit_inv(apid, matrix_mdev->matrix.apm, AP_DEVICES) {
+		/*
+		 * If the adapter is not in the host's AP configuration, it will
+		 * be due to one of two reasons:
+		 * 1. The adapter is over-provisioned.
+		 * 2. The adapter was removed from the host's
+		 *    configuration in which case it will already have
+		 *    been processed by the on_config_changed callback.
+		 * In either case, we should skip the filtering and
+		 * continue examining APIDs.
+		 */
+		if (!test_bit_inv(apid, (unsigned long *)matrix_dev->info.apm))
+			continue;
+
 		for_each_set_bit_inv(apqi, matrix_mdev->matrix.aqm, AP_DOMAINS) {
 			/*
-			 * If the APQN is not bound to the vfio_ap device
-			 * driver, then we can't assign it to the guest's
-			 * AP configuration. The AP architecture won't
-			 * allow filtering of a single APQN, so let's filter
-			 * the APID since an adapter represents a physical
-			 * hardware device.
+			 * If the domain is not in the host's AP configuration,
+			 * it will for one of two reasons:
+			 * 1. The domain is over-provisioned.
+			 * 2. The domain was removed from the host's
+			 *    configuration in which case it will already have
+			 *    been processed by the on_config_changed callback.
+			 * In either case, we should skip the filtering and
+			 * continue examining APQIs.
 			 */
+			if (!test_bit_inv(apqi,
+					  (unsigned long *)matrix_dev->info.aqm))
+				continue;
+
 			apqn = AP_MKQID(apid, apqi);
 			q = vfio_ap_mdev_get_queue(matrix_mdev, apqn);
+
 			if (!q || q->reset_status.response_code) {
 				clear_bit_inv(apid,
 					      matrix_mdev->shadow_apcb.apm);
-- 
2.41.0