Re: [PATCH v4 6/7] s390: ap: Cleanup on removing the AP device

From: Pierre Morel
Date: Mon Mar 11 2019 - 04:31:12 EST

On 08/03/2019 23:43, Tony Krowiak wrote:
On 2/22/19 10:29 AM, Pierre Morel wrote:
When the device is remove, we must make sure to
clear the interruption and reset the AP device.

We also need to clear the CRYCB of the guest.

Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
 drivers/s390/crypto/vfio_ap_drv.c | 35 +++++++++++++++++++++++++++++++++++
 drivers/s390/crypto/vfio_ap_ops.c | 3 ++-
 drivers/s390/crypto/vfio_ap_private.h | 3 +++
 3 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
index eca0ffc..e5d91ff 100644
--- a/drivers/s390/crypto/vfio_ap_drv.c
+++ b/drivers/s390/crypto/vfio_ap_drv.c
@@ -5,6 +5,7 @@
ÂÂ * Copyright IBM Corp. 2018
ÂÂ *
ÂÂ * Author(s): Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
+ *ÂÂÂÂÂÂÂÂÂ Pierre Morel <pmorel@xxxxxxxxxxxxx>
ÂÂ */
 #include <linux/module.h>
@@ -12,6 +13,8 @@
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <asm/facility.h>
+#include <linux/bitops.h>
+#include <linux/kvm_host.h>
 #include "vfio_ap_private.h"
 #define VFIO_AP_ROOT_NAME "vfio_ap"
@@ -61,6 +64,33 @@ static int vfio_ap_queue_dev_probe(struct ap_device *apdev)
+ * vfio_ap_update_crycb
+ * @q: A pointer to the queue being removed
+ *
+ * We clear the APID of the queue, making this queue unusable for the guest.
+ * After this function we can reset the queue without to fear a race with
+ * the guest to access the queue again.
+ * We do not fear race with the host as we still get the device.
+ */
+static void vfio_ap_update_crycb(struct vfio_ap_queue *q)
+ÂÂÂ struct ap_matrix_mdev *matrix_mdev = q->matrix_mdev;
+ÂÂÂ if (!matrix_mdev)
+ÂÂÂÂÂÂÂ return;
+ÂÂÂ clear_bit_inv(AP_QID_CARD(q->apqn), matrix_mdev->matrix.apm);
+ÂÂÂ if (!matrix_mdev->kvm)
+ÂÂÂÂÂÂÂ return;
+ÂÂÂ kvm_arch_crypto_set_masks(matrix_mdev->kvm,
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ matrix_mdev->matrix.apm,
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ matrix_mdev->matrix.aqm,
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ matrix_mdev->matrix.adm);
ÂÂ * vfio_ap_queue_dev_remove:
ÂÂ *
ÂÂ * Free the associated vfio_ap_queue structure
@@ -70,6 +100,11 @@ static void vfio_ap_queue_dev_remove(struct ap_device *apdev)
ÂÂÂÂÂ struct vfio_ap_queue *q;
ÂÂÂÂÂ q = dev_get_drvdata(&apdev->device);
+ÂÂÂ if (!q)
+ÂÂÂÂÂÂÂ return;
+ÂÂÂ vfio_ap_update_crycb(q);
+ÂÂÂ vfio_ap_mdev_reset_queue(q);

Since the bit corresponding to the APID is cleared in the
vfio_ap_update_crycb() above, shouldn't all queues on that
card also be reset?

I do not think so.
The remove function will be called in a loop for all queues by the bus.
No need to clear all queues.

ÂÂÂÂÂ list_del(&q->list);
ÂÂÂÂÂ kfree(q);
diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 0196065..5b9bb33 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -59,6 +59,7 @@ int vfio_ap_mdev_reset_queue(struct vfio_ap_queue *q)
ÂÂÂÂÂÂÂÂÂÂÂÂÂ if (retry <= 0)
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ pr_warn("%s: queue 0x%04x not empty\n",
+ÂÂÂÂÂÂÂÂÂÂÂ vfio_ap_free_irq(q);

Shouldn't this be done for the response codes that terminate this loop
such as those caught by the default case?

I do not think so, the error code is returned and the caller may want to reset the queue again.
I think that doing the free inside the call to reset is not right.
I will investigate in this direction.


Pierre Morel
Linux/KVM/QEMU in BÃblingen - Germany