Re: [PATCH v2 6/7] s390: vfio-ap: handle bind and unbind of AP queue device

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On 5/6/19 6:55 AM, Pierre Morel wrote:
On 03/05/2019 23:14, Tony Krowiak wrote:
There is nothing preventing a root user from inadvertently unbinding an
AP queue device that is in use by a guest from the vfio_ap device driver
and binding it to a zcrypt driver. This can result in a queue being
accessible from both the host and a guest.

This patch introduces safeguards that prevent sharing of an AP queue
between the host when a queue device is unbound from the vfio_ap device
driver. In addition, this patch restores guest access to AP queue devices
bound to the vfio_ap driver if the queue's APQN is assigned to an mdev
device in use by a guest.

Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
---
  drivers/s390/crypto/vfio_ap_drv.c     |  12 +++-
  drivers/s390/crypto/vfio_ap_ops.c     | 100 +++++++++++++++++++++++++++++++++-
  drivers/s390/crypto/vfio_ap_private.h |   2 +
  3 files changed, 111 insertions(+), 3 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
index e9824c35c34f..c215978daf39 100644
--- a/drivers/s390/crypto/vfio_ap_drv.c
+++ b/drivers/s390/crypto/vfio_ap_drv.c
@@ -42,12 +42,22 @@ MODULE_DEVICE_TABLE(vfio_ap, ap_queue_ids);
  static int vfio_ap_queue_dev_probe(struct ap_device *apdev)
  {
+    struct ap_queue *queue = to_ap_queue(&apdev->device);
+
+    mutex_lock(&matrix_dev->lock);
+    vfio_ap_mdev_probe_queue(queue);
+    mutex_unlock(&matrix_dev->lock);
+
      return 0;
  }
  static void vfio_ap_queue_dev_remove(struct ap_device *apdev)
  {
-    /* Nothing to do yet */
+    struct ap_queue *queue = to_ap_queue(&apdev->device);
+
+    mutex_lock(&matrix_dev->lock);
+    vfio_ap_mdev_remove_queue(queue);
+    mutex_unlock(&matrix_dev->lock);
  }
  static void vfio_ap_matrix_dev_release(struct device *dev)
diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index ede45184eb67..40324951bd37 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -226,8 +226,6 @@ static struct device *vfio_ap_get_queue_dev(unsigned long apid,
                    &apqn, match_apqn);
  }
-
-
  static int vfio_ap_mdev_validate_masks(unsigned long *apm, unsigned long *aqm)
  {
      int ret;
@@ -259,6 +257,27 @@ static bool vfio_ap_queues_on_drv(unsigned long *apm, unsigned long *aqm)
      return true;
  }
+static bool vfio_ap_card_on_drv(struct ap_queue *queue, unsigned long *aqm)
+{
+    unsigned long apid, apqi;
+    struct device *dev;
+
+    apid = AP_QID_CARD(queue->qid);
+
+    for_each_set_bit_inv(apqi, aqm, AP_DOMAINS) {
+        if (queue->qid == AP_MKQID(apid, apqi))
+            continue;
+
+        dev = vfio_ap_get_queue_dev(apid, apqi);
+        if (!dev)
+            return false;
+
+        put_device(dev);
+    }
+
+    return true;
+}
+
  /**
   * assign_adapter_store
   *
@@ -1017,3 +1036,80 @@ void vfio_ap_mdev_unregister(void)
  {
      mdev_unregister_device(&matrix_dev->device);
  }
+
+static struct ap_matrix_mdev *vfio_ap_mdev_find_matrix_mdev(unsigned long apid,
+                                unsigned long apqi)
+{
+    struct ap_matrix_mdev *matrix_mdev;
+
+    list_for_each_entry(matrix_mdev, &matrix_dev->mdev_list, node) {
+        if (test_bit_inv(apid, matrix_mdev->matrix.apm) &&
+            test_bit_inv(apqi, matrix_mdev->matrix.aqm))
+            return matrix_mdev;
+    }
+
+    return NULL;
+}
+
+void vfio_ap_mdev_probe_queue(struct ap_queue *queue)
+{
+    struct ap_matrix_mdev *matrix_mdev;
+    unsigned long *shadow_apm, *shadow_aqm;
+    unsigned long apid = AP_QID_CARD(queue->qid);
+    unsigned long apqi = AP_QID_QUEUE(queue->qid);
+
+    /*
+     * Find the mdev device to which the APQN of the queue device being
+     * probed is assigned
+     */
+    matrix_mdev = vfio_ap_mdev_find_matrix_mdev(apid, apqi);
+
+    /* Check whether we found an mdev device and it is in use by a guest */
+    if (matrix_mdev && matrix_mdev->kvm) {
+        shadow_apm = matrix_mdev->shadow_crycb->apm;
+        shadow_aqm = matrix_mdev->shadow_crycb->aqm;
+        /*
+         * If the guest already has access to the adapter card
+         * referenced by APID or does not have access to the queues
+         * referenced by APQI, there is nothing to do here.
+         */
+        if (test_bit_inv(apid, shadow_apm) ||
+            !test_bit_inv(apqi, shadow_aqm))
+            return;
+
+        /*
+         * If each APQN with the APID of the queue being probed and an
+         * APQI in the shadow CRYCB references a queue device that is
+         * bound to the vfio_ap driver, then plug the adapter into the
+         * guest.
+         */
+        if (vfio_ap_card_on_drv(queue, shadow_aqm)) {
+            set_bit_inv(apid, shadow_apm);
+            vfio_ap_mdev_update_crycb(matrix_mdev);
+        }
+    }
+}
+
+void vfio_ap_mdev_remove_queue(struct ap_queue *queue)
+{
+    struct ap_matrix_mdev *matrix_mdev;
+    unsigned long apid = AP_QID_CARD(queue->qid);
+    unsigned long apqi = AP_QID_QUEUE(queue->qid);
+
+    matrix_mdev = vfio_ap_mdev_find_matrix_mdev(apid, apqi);
+
+    /*
+     * If the queue is assigned to the mdev device and the mdev device
+     * is in use by a guest, unplug the adapter referred to by the APID
+     * of the APQN of the queue being removed.
+     */
+    if (matrix_mdev && matrix_mdev->kvm) {
+        if (!test_bit_inv(apid, matrix_mdev->shadow_crycb->apm))
+            return;
+
+        clear_bit_inv(apid, matrix_mdev->shadow_crycb->apm);
+        vfio_ap_mdev_update_crycb(matrix_mdev);
+    }
+
+    vfio_ap_mdev_reset_queue(apid, apqi);
+}
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index e8457aa61976..6b1f7df5b979 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -87,5 +87,7 @@ struct ap_matrix_mdev {
  extern int vfio_ap_mdev_register(void);
  extern void vfio_ap_mdev_unregister(void);
+void vfio_ap_mdev_remove_queue(struct ap_queue *queue);
+void vfio_ap_mdev_probe_queue(struct ap_queue *queue);
  #endif /* _VFIO_AP_PRIVATE_H_ */



AFAIU the apmask/aqmask of the AP_BUS are replacing bind/unbind for the admin. Don't they?

Yes, these interfaces are used to bind/unbind.

Then why not suppress bind/unbind for ap_queues?

I did suppress them in a previous version, but I believe Harald
objected. I don't recall the reason. If any other maintainers
agree with this, I can reinstate that change. I personally would
prefer that. I think leaving the bind/unbind interfaces confuses
the issue.


Otherwise, it seems to me to handle correctly the disappearance of a card, which is the only thing that can happen from out of the firmware queue change requires configuration change and re-IPL.

You are correct.


Even still need testing, LGTM

I would welcome and appreciate additional testing, thanks in advance.







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