s390/vfio-ap: add s390dbf logging to the handle_pqap function

This patch adds s390dbf logging to the function that handles interception
of the PQAP(AQIC) instruction. Several items of data are validated before
ultimately calling the functions that execute the PQAP(AQIC) instruction on
behalf of the guest to which the queue for which interrupts are being
enabled or disabled is attached.

Currently, the handle_pqap function sets status response code 01 (queue not
available) in the status word that is normally returned from the
PQAP(AQIC) instruction under the following conditions:

* Set when the function pointer to the handler is not set in the
kvm_s390_crypto object (i.e., the PQAP hook is not registered).

* Set when the KVM pointer is not set in the ap_matrix_mdev object
(i.e., the matrix mdev is not passed through to a guest).

* Set when the queue for which interrupts are being enabled or
disabled is either not bound to the vfio_ap device driver or not assigned
to the matrix mdev.

Setting the response code returned to userspace without also logging a
message in the kernel makes it impossible to determine whether the response
was due to an error detected by the vfio_ap device driver or because the
response code was returned by the firmware in response to the PQAP(AQIC)
instruction, so this patch logs a message to the s390dbf log for the
vfio_ap device driver for each of the situations described above.

Signed-off-by: Tony Krowiak <[e-mail]>
Reviewed-by: Matthew Rosato <[e-mail]>
Acked-by: Heiko Carstens <[e-mail]>
Signed-off-by: Vasily Gorbik <[e-mail]>

drivers/s390/crypto/vfio_ap_ops.c

···
 #include <linux/bitops.h>
 #include <linux/kvm_host.h>
 #include <linux/module.h>
+#include <linux/uuid.h>
 #include <asm/kvm.h>
 #include <asm/zcrypt.h>
 
 #include "vfio_ap_private.h"
+#include "vfio_ap_debug.h"
 
 #define VFIO_AP_MDEV_TYPE_HWVIRT "passthrough"
 #define VFIO_AP_MDEV_NAME_HWVIRT "VFIO AP Passthrough Device"
···
 }
 
 /**
+ * vfio_ap_le_guid_to_be_uuid - convert a little endian guid array into an array
+ *				of big endian elements that can be passed by
+ *				value to an s390dbf sprintf event function to
+ *				format a UUID string.
+ *
+ * @guid: the object containing the little endian guid
+ * @uuid: a six-element array of long values that can be passed by value as
+ *	  arguments for a formatting string specifying a UUID.
+ *
+ * The S390 Debug Feature (s390dbf) allows the use of "%s" in the sprintf
+ * event functions if the memory for the passed string is available as long as
+ * the debug feature exists. Since a mediated device can be removed at any
+ * time, it's name can not be used because %s passes the reference to the string
+ * in memory and the reference will go stale once the device is removed .
+ *
+ * The s390dbf string formatting function allows a maximum of 9 arguments for a
+ * message to be displayed in the 'sprintf' view. In order to use the bytes
+ * comprising the mediated device's UUID to display the mediated device name,
+ * they will have to be converted into an array whose elements can be passed by
+ * value to sprintf. For example:
+ *
+ * guid array: { 83, 78, 17, 62, bb, f1, f0, 47, 91, 4d, 32, a2, 2e, 3a, 88, 04 }
+ * mdev name: 62177883-f1bb-47f0-914d-32a22e3a8804
+ * array returned: { 62177883, f1bb, 47f0, 914d, 32a2, 2e3a8804 }
+ * formatting string: "%08lx-%04lx-%04lx-%04lx-%02lx%04lx"
+ */
+static void vfio_ap_le_guid_to_be_uuid(guid_t *guid, unsigned long *uuid)
+{
+	/*
+	 * The input guid is ordered in little endian, so it needs to be
+	 * reordered for displaying a UUID as a string. This specifies the
+	 * guid indices in proper order.
+	 */
+	uuid[0] = le32_to_cpup((__le32 *)guid);
+	uuid[1] = le16_to_cpup((__le16 *)&guid->b[4]);
+	uuid[2] = le16_to_cpup((__le16 *)&guid->b[6]);
+	uuid[3] = *((__u16 *)&guid->b[8]);
+	uuid[4] = *((__u16 *)&guid->b[10]);
+	uuid[5] = *((__u32 *)&guid->b[12]);
+}
+
+/**
  * handle_pqap - PQAP instruction callback
  *
  * @vcpu: The vcpu on which we received the PQAP instruction
···
 {
 	uint64_t status;
 	uint16_t apqn;
+	unsigned long uuid[6];
 	struct vfio_ap_queue *q;
 	struct ap_queue_status qstatus = {
 			       .response_code = AP_RESPONSE_Q_NOT_AVAIL, };
 	struct ap_matrix_mdev *matrix_mdev;
 
-	/* If we do not use the AIV facility just go to userland */
-	if (!(vcpu->arch.sie_block->eca & ECA_AIV))
-		return -EOPNOTSUPP;
-
 	apqn = vcpu->run->s.regs.gprs[0] & 0xffff;
-	mutex_lock(&matrix_dev->lock);
 
-	if (!vcpu->kvm->arch.crypto.pqap_hook)
+	/* If we do not use the AIV facility just go to userland */
+	if (!(vcpu->arch.sie_block->eca & ECA_AIV)) {
+		VFIO_AP_DBF_WARN("%s: AIV facility not installed: apqn=0x%04x, eca=0x%04x\n",
+				 __func__, apqn, vcpu->arch.sie_block->eca);
+
+		return -EOPNOTSUPP;
+	}
+
+	mutex_lock(&matrix_dev->lock);
+	if (!vcpu->kvm->arch.crypto.pqap_hook) {
+		VFIO_AP_DBF_WARN("%s: PQAP(AQIC) hook not registered with the vfio_ap driver: apqn=0x%04x\n",
+				 __func__, apqn);
 		goto out_unlock;
+	}
+
 	matrix_mdev = container_of(vcpu->kvm->arch.crypto.pqap_hook,
 				   struct ap_matrix_mdev, pqap_hook);
 
 	/* If the there is no guest using the mdev, there is nothing to do */
-	if (!matrix_mdev->kvm)
+	if (!matrix_mdev->kvm) {
+		vfio_ap_le_guid_to_be_uuid(&matrix_mdev->mdev->uuid, uuid);
+		VFIO_AP_DBF_WARN("%s: mdev %08lx-%04lx-%04lx-%04lx-%04lx%08lx not in use: apqn=0x%04x\n",
+				 __func__, uuid[0],  uuid[1], uuid[2],
+				 uuid[3], uuid[4], uuid[5], apqn);
 		goto out_unlock;
+	}
 
 	q = vfio_ap_get_queue(matrix_mdev, apqn);
-	if (!q)
+	if (!q) {
+		VFIO_AP_DBF_WARN("%s: Queue %02x.%04x not bound to the vfio_ap driver\n",
+				 __func__, AP_QID_CARD(apqn),
+				 AP_QID_QUEUE(apqn));
 		goto out_unlock;
+	}
 
 	status = vcpu->run->s.regs.gprs[1];