Re: [PATCH v7 02/15] s390/vfio-ap: Data structures for facilitating vfio device migration
From: Anthony Krowiak
Date: Mon Oct 05 2026 - 11:25:30 EST
On 8/10/26 9:45 AM, Jason J. Herne wrote:
On 8/7/26 6:18 PM, Anthony Krowiak wrote:
Creates the data structures used to facilitate state transitions during
vfio device migration.
Signed-off-by: Anthony Krowiak <akrowiak@xxxxxxxxxxxxx>
---
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
Typo. I think you wanted 'comprised' here.
I did, thanks.
Reviewed-by: Jason J. Herne <jjherne@xxxxxxxxxxxxx>