[PATCH v7 02/15] s390/vfio-ap: Data structures for facilitating vfio device migration

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

Creates the data structures used to facilitate state transitions during
vfio device migration.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/Makefile            |   2 +-
 drivers/s390/crypto/vfio_ap_migration.c | 113 ++++++++++++++++++++++++
 drivers/s390/crypto/vfio_ap_private.h   |   5 ++
 3 files changed, 119 insertions(+), 1 deletion(-)
 create mode 100644 drivers/s390/crypto/vfio_ap_migration.c

diff --git a/drivers/s390/crypto/Makefile b/drivers/s390/crypto/Makefile
index e83c6603c858..20f29184825a 100644
--- a/drivers/s390/crypto/Makefile
+++ b/drivers/s390/crypto/Makefile
@@ -34,5 +34,5 @@ pkey-uv-objs := pkey_uv.o
 obj-$(CONFIG_PKEY_UV) += pkey-uv.o
 
 # adjunct processor matrix
-vfio_ap-objs := vfio_ap_drv.o vfio_ap_ops.o
+vfio_ap-objs := vfio_ap_drv.o vfio_ap_ops.o vfio_ap_migration.o
 obj-$(CONFIG_VFIO_AP) += vfio_ap.o
diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
new file mode 100644
index 000000000000..374d3a67cb21
--- /dev/null
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -0,0 +1,113 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Drives vfio_ap mdev migration.
+ *
+ * Copyright IBM Corp. 2025
+ */
+#include "vfio_ap_private.h"
+
+/* Magic number and version for the vfio_ap_config migration blob */
+#define VFIO_AP_MIG_MAGIC			0x76666170U  /* "vfap" */
+#define VFIO_AP_MIG_VERSION			1U
+
+/**
+ * struct vfio_ap_migration_file
+ *
+ * This object is used for chunk processing of multiple reads and writes of
+ * AP configuration information.
+ *
+ * @filp:	file stream used to read or write AP configuration data
+ * @ap_config:	object used to store AP configuration data between read or write
+ *		calls
+ * @config_sz:	the size (in bytes) of @ap_config
+ */
+struct vfio_ap_migration_file {
+	struct file		*filp;
+	struct vfio_ap_config	*ap_config;
+	unsigned long		config_sz;
+};
+
+/**
+ * struct vfio_ap_migration_data:
+ *
+ * Manages the migration state for the VFIO device that maintains the AP
+ * configuration of the guest being migrated.
+ *
+ * @mig_state:		the current migration state
+ * @resuming_mig_file:	the object used to restore the state of the vfio-ap
+ *			device on the destination host.
+ * @stop_copy_mig_file:	the object used to store the AP configuration of the
+ *			source guest for transfer to the destination host.
+ */
+struct vfio_ap_migration_data {
+	enum vfio_device_mig_state	mig_state;
+	struct vfio_ap_migration_file	resuming_mig_file;
+	struct vfio_ap_migration_file	stop_copy_mig_file;
+};
+
+/**
+ * struct vfio_ap_queue_info - the information for an AP queue
+ *
+ * @data: contains the queue information returned in GR2 from the PQAP(TAPQ)
+ *	  command
+ * @apqn: the APQN of the queue
+ * @reserved: padding to ensure consistent structure size across platforms
+ */
+struct vfio_ap_queue_info {
+	u64 data;
+	u16 apqn;
+	u8  reserved[6];
+};
+
+/**
+ * struct vfio_ap_config:
+ *
+ * Stores the state of a guest's AP configuration.
+ *
+ * VFIO device migration state transition from STOP to STOP_COPY:
+ * -------------------------------------------------------------
+ * When the migration state transitions from STOP to STOP_COPY, the vfio_ap device
+ * driver will open a file stream in read-only mode and return the fd to userspace.
+ * This fd is used during the STOP_COPY phase to read the current state of the
+ * vfio-ap device on the source host. In response, the driver will store the
+ * source guest's AP configuration data in a vfio_ap_config object and copy it to
+ * userspace.
+ *
+ * VFIO device migration state transition from STOP to RESUMING:
+ * ------------------------------------------------------------
+ * When the VFIO migration state transitions from STOP to RESUMING,
+ * the vfio_ap device driver will open a file stream in write-only mode and
+ * return the fd to userspace. This fd is used during the RESUMING phase to
+ * write the source guest's vfio_ap_config data that was read in during the
+ * STOP_COPY phase to the vfio_ap device driver on the destination host. In
+ * response, the device driver will copy the data sent from userspace to a
+ * vfio_ap_config instance which is then used to update the destination guest's
+ * AP configuration.
+ *
+ * Since the source and destination hosts may be running different versions of
+ * the linux kernel, the vfio_ap_config object provides two fields (@magic and
+ * @version) which must be set by the source device driver and verified by the
+ * destination device driver to ensure the migration ABI of the source and
+ * destination hosts are compatible.
+ *
+ * Note: Since a guest's AP configuration could be comprise of a large number of
+ *	 AP queue devices, a vfio_ap_config object should be allocated using
+ *	 kvzalloc.
+ *
+ * @magic:	identifies this as a valid vfio_ap_config migration blob;
+ *		must equal VFIO_AP_MIG_MAGIC
+ * @version:	layout version; must equal VFIO_AP_MIG_VERSION
+ * @num_queues:	the number of queues passed through to the guest
+ * @reserved:	padding to ensure proper alignment of @adm
+ * @adm:	bitmap specifying the control domains in the AP configuration
+ * @qinfo:	an array of vfio_ap_queue_info objects, each specifying the
+ *		queue information for a queue passed through to the guest
+ */
+struct vfio_ap_config {
+	u32				magic;
+	u32				version;
+	u32				num_queues;
+	u8				reserved[4];
+	u64				adm[DIV_ROUND_UP(AP_DOMAINS, 64)];
+	struct vfio_ap_queue_info	qinfo[] __counted_by(num_queues);
+};
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index 9677e49554d7..2b542648964b 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -91,6 +91,9 @@ struct ap_queue_table {
 	DECLARE_HASHTABLE(queues, 8);
 };
 
+/* Forward declaration for migration data structure */
+struct vfio_ap_migration_data;
+
 /**
  * struct ap_matrix_mdev - Contains the data associated with a matrix mediated
  *			   device.
@@ -110,6 +113,7 @@ struct ap_queue_table {
  * @aqm_add:	bitmap of APQIs added to the host's AP configuration
  * @adm_add:	bitmap of control domain numbers added to the host's AP
  *		configuration
+ * @mig_data:  vfio device migration data
  */
 struct ap_matrix_mdev {
 	struct vfio_device vdev;
@@ -125,6 +129,7 @@ struct ap_matrix_mdev {
 	DECLARE_BITMAP(apm_add, AP_DEVICES);
 	DECLARE_BITMAP(aqm_add, AP_DOMAINS);
 	DECLARE_BITMAP(adm_add, AP_DOMAINS);
+	struct vfio_ap_migration_data *mig_data;
 };
 
 /**
-- 
2.53.0