Re: [PATCH v17 06/15] s390/vfio-ap: refresh guest's APCB by filtering APQNs assigned to mdev

Tony Krowiak <akrowiak@xxxxxxxxxxxxx> · Tue, 11 Jan 2022 16:19:06 -0500

On 12/27/21 03:53, Halil Pasic wrote:
On Thu, 21 Oct 2021 11:23:23 -0400
Tony Krowiak <akrowiak@xxxxxxxxxxxxx> wrote:

Refresh the guest's APCB by filtering the APQNs assigned to the matrix mdev
that do not reference an AP queue device bound to the vfio_ap device
driver. The mdev's APQNs will be filtered according to the following rules:

* The APID of each adapter and the APQI of each domain that is not in the
host's AP configuration is filtered out.

* The APID of each adapter comprising an APQN that does not reference a
queue device bound to the vfio_ap device driver is filtered. The APQNs
are derived from the Cartesian product of the APID of each adapter and
APQI of each domain assigned to the mdev.

The control domains that are not assigned to the host's AP configuration
will also be filtered before assigning them to the guest's APCB.
The v16 version used to filer on queue removal from vfio_ap, which makes
a ton of sense.

This version will "filter back" the queues once these become bound, but
if a queue is removed form vfio_ap, we don't seem to care to filter. Is
this intentional?

See patch the changes to the vfio_ap_mdev_remove_queue function in patch 
09/15,
s390/vfio-ap: allow hot plug/unplug of AP resources using mdev device

Now that I look at that patch, I should probably rearrange this patch to 
also do
filtering on queue removal, but only do the hotplug stuff in patch 09.


Also we could probably do the filtering incrementally. In a sense that
at a time only so much changes, and we know that the invariant was
preserved without that change. But that would probably end up trading
complexity for cycles. I will trust your judgment and your tests on this
matter.

I am not entirely clear on what you are suggesting. I think you are
suggesting that there may not be a need to look at every APQN
assigned to the mdev when an adapter or domain is assigned or
unassigned or a queue is probed or removed. Maybe you can clarify
what you are suggesting here.


Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
---
  drivers/s390/crypto/vfio_ap_ops.c | 66 ++++++++++++++++++++++++++++++-
  1 file changed, 64 insertions(+), 2 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 4305177029bf..46c179363aca 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -314,6 +314,62 @@ static void vfio_ap_matrix_init(struct ap_config_info *info,
  	matrix->adm_max = info->apxa ? info->Nd : 15;
  }
  
+static void vfio_ap_mdev_filter_cdoms(struct ap_matrix_mdev *matrix_mdev)
+{
+	bitmap_and(matrix_mdev->shadow_apcb.adm, matrix_mdev->matrix.adm,
+		   (unsigned long *)matrix_dev->info.adm, AP_DOMAINS);
+}
+
+/*
+ * vfio_ap_mdev_filter_matrix - copy the mdev's AP configuration to the KVM
+ *				guest's APCB then filter the APIDs that do not
+ *				comprise at least one APQN that references a
+ *				queue device bound to the vfio_ap device driver.
+ *
+ * @matrix_mdev: the mdev whose AP configuration is to be filtered.
+ */
+static void vfio_ap_mdev_filter_matrix(struct ap_matrix_mdev *matrix_mdev)
+{
+	int ret;
+	unsigned long apid, apqi, apqn;
+
+	ret = ap_qci(&matrix_dev->info);
+	if (ret)
+		return;
+
+	vfio_ap_matrix_init(&matrix_dev->info, &matrix_mdev->shadow_apcb);
+
+	/*
+	 * Copy the adapters, domains and control domains to the shadow_apcb
+	 * from the matrix mdev, but only those that are assigned to the host's
+	 * AP configuration.
+	 */
+	bitmap_and(matrix_mdev->shadow_apcb.apm, matrix_mdev->matrix.apm,
+		   (unsigned long *)matrix_dev->info.apm, AP_DEVICES);
+	bitmap_and(matrix_mdev->shadow_apcb.aqm, matrix_mdev->matrix.aqm,
+		   (unsigned long *)matrix_dev->info.aqm, AP_DOMAINS);
+
+	for_each_set_bit_inv(apid, matrix_mdev->shadow_apcb.apm, AP_DEVICES) {
+		for_each_set_bit_inv(apqi, matrix_mdev->shadow_apcb.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 if we're
+			 * filtering APIDs, then filter the APID; otherwise,
+			 * filter the APQI.
+			 */
+			apqn = AP_MKQID(apid, apqi);
+			if (!vfio_ap_mdev_get_queue(matrix_mdev, apqn)) {
+				clear_bit_inv(apid,
+					      matrix_mdev->shadow_apcb.apm);
+				break;
+			}
+		}
+	}
+}
+
  static int vfio_ap_mdev_probe(struct mdev_device *mdev)
  {
  	struct ap_matrix_mdev *matrix_mdev;
@@ -703,6 +759,7 @@ static ssize_t assign_adapter_store(struct device *dev,
  		goto share_err;
  
  	vfio_ap_mdev_link_adapter(matrix_mdev, apid);
+	vfio_ap_mdev_filter_matrix(matrix_mdev);
  	ret = count;
  	goto done;
  
@@ -771,6 +828,7 @@ static ssize_t unassign_adapter_store(struct device *dev,
  
  	clear_bit_inv((unsigned long)apid, matrix_mdev->matrix.apm);
  	vfio_ap_mdev_unlink_adapter(matrix_mdev, apid);
+	vfio_ap_mdev_filter_matrix(matrix_mdev);
  	ret = count;
  done:
  	mutex_unlock(&matrix_dev->lock);
@@ -874,6 +932,7 @@ static ssize_t assign_domain_store(struct device *dev,
  		goto share_err;
  
  	vfio_ap_mdev_link_domain(matrix_mdev, apqi);
+	vfio_ap_mdev_filter_matrix(matrix_mdev);
  	ret = count;
  	goto done;
  
@@ -942,6 +1001,7 @@ static ssize_t unassign_domain_store(struct device *dev,
  
  	clear_bit_inv((unsigned long)apqi, matrix_mdev->matrix.aqm);
  	vfio_ap_mdev_unlink_domain(matrix_mdev, apqi);
+	vfio_ap_mdev_filter_matrix(matrix_mdev);
  	ret = count;
  
  done:
@@ -995,6 +1055,7 @@ static ssize_t assign_control_domain_store(struct device *dev,
  	 * number of control domains that can be assigned.
  	 */
  	set_bit_inv(id, matrix_mdev->matrix.adm);
+	vfio_ap_mdev_filter_cdoms(matrix_mdev);
  	ret = count;
  done:
  	mutex_unlock(&matrix_dev->lock);
@@ -1042,6 +1103,7 @@ static ssize_t unassign_control_domain_store(struct device *dev,
  	}
  
  	clear_bit_inv(domid, matrix_mdev->matrix.adm);
+	clear_bit_inv(domid, matrix_mdev->shadow_apcb.adm);
  	ret = count;
  done:
  	mutex_unlock(&matrix_dev->lock);
@@ -1179,8 +1241,6 @@ static int vfio_ap_mdev_set_kvm(struct ap_matrix_mdev *matrix_mdev,
  		kvm_get_kvm(kvm);
  		matrix_mdev->kvm = kvm;
  		kvm->arch.crypto.data = matrix_mdev;
-		memcpy(&matrix_mdev->shadow_apcb, &matrix_mdev->matrix,
-		       sizeof(struct ap_matrix));
  		kvm_arch_crypto_set_masks(kvm, matrix_mdev->shadow_apcb.apm,
  					  matrix_mdev->shadow_apcb.aqm,
  					  matrix_mdev->shadow_apcb.adm);
@@ -1536,6 +1596,8 @@ int vfio_ap_mdev_probe_queue(struct ap_device *apdev)
  	q->apqn = to_ap_queue(&apdev->device)->qid;
  	q->saved_isc = VFIO_AP_ISC_INVALID;
  	vfio_ap_queue_link_mdev(q);
+	if (q->matrix_mdev)
+		vfio_ap_mdev_filter_matrix(q->matrix_mdev);
  	dev_set_drvdata(&apdev->device, q);
  	mutex_unlock(&matrix_dev->lock);
  







