[PATCH v6 00/15] s390/vfio-ap: Add live guest migration support

[PATCH v6 00/15] s390/vfio-ap: Add live guest migration support

[Anthony Krowiak]

This patch series implements live guest migration support for KVM guests
with s390 AP (Adjunct Processor) devices passed through via the VFIO
mediated device framework.

Background
~~~~~~~~~~

The vfio-ap device driver differs from typical VFIO device drivers in that
it does not virtualize a physical device. Instead, it manages AP
configuration metadata identifying the AP adapters, domains, and control
domains to which a guest will be granted access. These AP resources are
configured by assigning them to a vfio-ap mediated device via its sysfs
assignment interfaces. When the fd for the VFIO device is opened by
userspace, the vfio_ap device driver sets the guest's AP configuration
from the metadata stored with the mediated device. As such, the AP devices
are not accessed directly through the vfio_ap driver, so the driver has no
internal AP device state to migrate. What it does migrate is the AP
configuration metadata of the source guest.

Implementation Approach
~~~~~~~~~~~~~~~~~~~~~~~

This series implements the VFIO migration protocol using the STOP_COPY
migration flow. The key aspects are:

1. On transition of the migration state from STOP to STOP_COPY
   - The vfio_ap device driver creates a filestream for userspace to use to
     read the guest's AP configuration from the mdev

2. During the STOP_COPY phase
   - Userspace uses the filestream created in #1 to read the source guest's
     AP configuration
   - The vfio_ap device driver copies the source guest's AP configuration
     information to userspace

3. On transition of the migration state from STOP to RESUMING
   - The vfio_ap device driver creates a filestream for userspace to use to
     write the source guest's AP configuration information so it can be
     restored to the mdev on the destination host.

4. During the RESUMING phase
   - Userspace uses the filestream created in #3 to send the source guest's
     AP configuration information to the vfio_ap device driver on the
     destination host.
   - The vfio_ap device driver first verifies the source guest's AP
     configuration is compatible with the destination host's.
   - The driver restores AP configuration to the mdev on the destination
     host which automatically hot plugs the AP resources identified
     therein.

5. Documentation
   - Add live guest migration chapter to vfio-ap.rst

Compatibility Validation
~~~~~~~~~~~~~~~~~~~~~~~~

The series includes comprehensive validation to ensure source and
destination AP configurations are compatible. For each queue, the following
characteristics must match:

- AP type (target must be same or newer than source)
- Installed facilities (APSC, APQKM, AP4KC, SLCF)
- Operating mode (CCA, Accelerator, XCP)
- APXA facility setting
- Classification (native vs stateless functions)
- Queue usability (binding/associated state)

When incompatibilities are detected, migration fails with detailed error
messages identifying the specific queue and characteristic that caused
the failure.

Configuration Management
~~~~~~~~~~~~~~~~~~~~~~~~

This implementation does not prevent configuration changes during
migration. Configuration stability is an orchestration-layer
responsibility, consistent with other VFIO device types. The driver's
role is to validate configurations and provide clear diagnostics when
incompatibilities are detected, enabling orchestration tools to implement
appropriate policies.

QEMU patches exploiting this series:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
https://lore.kernel.org/qemu-devel/20260409141352.997844-1-akrowiak@linux.ibm.com/

Change log v5 => v6:
~~~~~~~~~~~~~~~~~~~
Patch 1: Provide function to get the number of queues assigned to mdev
* Replaced nested loop over matrix_mdev->apm and matrix_mdev->aqm to count
  the number of queues with bitmap_weight calls to reduce the number of
  external function calls.
Patch 3: Functions to initialize/release vfio device migration data
* Fixed error path bug in vfio_ap_mdev_set_kvm function; reset pqap hook
  pointer (supposedly fixed in v4 but somehow got lost).
* In the vfio_ap_mdev_prove() function, moved call to 
  vfio_ap_init_migration_capabilities() before the mutex_lock, and pushed
  the mutex_lock to after vfio_register_emulated_iommu_dev() succeeds to
  avoid ABBA deadlock due to lock ordering between probe and open of vfio
  device.
  
Patch 7: File ops called to save the vfio device migration state
* Removed matrix_mdev null check in validate_stop_copy_read_parms().
  vfio_ap_open_file_stream() now takes a 
  vfio_device_try_get_registration() pin, so matrix_mdev is guaranteed
  live for the entire lifetime of the migration fd
* The ap_configuration->num_queues is now set before the loop that writes
  qinfo[] in the vfio_ap_get_config() function
  
Patch 9: Add method to set a new guest AP configuration
* Restored original version of vfio_ap_mdev_unlink_fr_queues function that 
  somehow got corrupted with last patch submission

Anthony Krowiak (15):
  s390/vfio-ap: Provide function to get the number of queues assigned to
    mdev
  s390/vfio-ap: Data structures for facilitating vfio device migration
  s390/vfio-ap: Functions to initialize/release vfio device migration
    data
  s390/vfio-ap: Reset migration state in VFIO_DEVICE_RESET ioctl handler
  s390-vfio-ap: Callback to get/set vfio device mig state during guest
    migration
  s390/vfio-ap: Transition guest migration state from STOP to STOP_COPY
  s390/vfio-ap: File ops called to save the vfio device migration state
  s390/vfio-ap: Transition device migration state from STOP to RESUMING
  s390/vfio-ap: Add method to set a new guest AP configuration
  s390/vfio-ap: File ops called to resume the vfio device migration
  s390/vfio-ap: Transition device migration state to STOP
  s390/vfio-ap: Transition device migration state from STOP to RUNNING
    and vice versa
  s390/vfio-ap: Callback to get the size of data to be migrated during
    guest migration
  s390/vfio-ap: Add 'migratable' feature to sysfs 'features' attribute
  s390/vfio-ap: Add live guest migration chapter to vfio-ap.rst

 Documentation/arch/s390/vfio-ap.rst     |  616 +++++++--
 drivers/s390/crypto/Makefile            |    2 +-
 drivers/s390/crypto/vfio_ap_drv.c       |    4 +-
 drivers/s390/crypto/vfio_ap_migration.c | 1530 +++++++++++++++++++++++
 drivers/s390/crypto/vfio_ap_ops.c       |  301 +++--
 drivers/s390/crypto/vfio_ap_private.h   |   73 ++
 6 files changed, 2318 insertions(+), 208 deletions(-)
 create mode 100644 drivers/s390/crypto/vfio_ap_migration.c

-- 
2.53.0

[PATCH v6 01/15] s390/vfio-ap: Provide function to get the number of queues assigned to mdev

[Anthony Krowiak]

Provides a function that returns the number of queues that are or will be
passed through to a guest when the mdev is attached to a guest.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_ops.c     | 8 ++++++++
 drivers/s390/crypto/vfio_ap_private.h | 2 ++
 2 files changed, 10 insertions(+)

diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 44b3a1dcc1b3..36786d70a88f 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -2098,6 +2098,14 @@ static void vfio_ap_mdev_request(struct vfio_device *vdev, unsigned int count)
 	release_update_locks_for_mdev(matrix_mdev);
 }
 
+int vfio_ap_mdev_get_num_queues(struct ap_matrix *ap_matrix)
+{
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	return bitmap_weight(ap_matrix->apm, AP_DEVICES) *
+	       bitmap_weight(ap_matrix->aqm, AP_DOMAINS);
+}
+
 static int vfio_ap_mdev_get_device_info(unsigned long arg)
 {
 	unsigned long minsz;
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index 9bff666b0b35..9677e49554d7 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -152,6 +152,8 @@ struct vfio_ap_queue {
 	struct work_struct reset_work;
 };
 
+int vfio_ap_mdev_get_num_queues(struct ap_matrix *ap_matrix);
+
 int vfio_ap_mdev_register(void);
 void vfio_ap_mdev_unregister(void);
 
-- 
2.53.0

[PATCH v6 02/15] s390/vfio-ap: Data structures for facilitating vfio device migration

[Anthony Krowiak]

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 | 72 +++++++++++++++++++++++++
 drivers/s390/crypto/vfio_ap_private.h   |  5 ++
 3 files changed, 78 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..fc3b2e154ad8
--- /dev/null
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Drives vfio_ap mdev migration.
+ *
+ * Copyright IBM Corp. 2025
+ */
+#include "vfio_ap_private.h"
+
+/**
+ * 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 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 - the guest's AP configuration
+ *
+ * @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				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

[PATCH v6 03/15] s390/vfio-ap: Functions to initialize/release vfio device migration data

[Anthony Krowiak]

Provides the functions that initialize and release the data structures
used during live guest migration:

* vfio_ap_init_migration_capabilities

  Sets the migration flags and vfio_migration_ops structure into the
  vfio_device object when the mdev is probed.

* vfio_ap_init_migration_data

  Allocates and initializes the object used to maintain the state of the
  VFIO migration. It is called when the VFIO device is opened.

* vfio_ap_release_migration_data

  Frees the memory of the object used to maintain the VFIO migration state.
  It is called when the VFIO device release callback is invoked and when
  the VFIO device is closed.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_migration.c | 80 +++++++++++++++++++++++++
 drivers/s390/crypto/vfio_ap_ops.c       | 64 +++++++++++++++++---
 drivers/s390/crypto/vfio_ap_private.h   |  4 ++
 3 files changed, 140 insertions(+), 8 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index fc3b2e154ad8..ae0bd1f415fe 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -4,6 +4,7 @@
  *
  * Copyright IBM Corp. 2025
  */
+#include <linux/file.h>
 #include "vfio_ap_private.h"
 
 /**
@@ -70,3 +71,82 @@ struct vfio_ap_config {
 	u64				adm[DIV_ROUND_UP(AP_DOMAINS, 64)];
 	struct vfio_ap_queue_info	qinfo[] __counted_by(num_queues);
 };
+
+static struct file *vfio_ap_set_state(struct vfio_device *vdev,
+				      enum vfio_device_mig_state  new_state)
+{
+	return NULL;
+}
+
+static int vfio_ap_get_state(struct vfio_device *vdev,
+			     enum vfio_device_mig_state  *current_state)
+{
+	return -EOPNOTSUPP;
+}
+
+static int vfio_ap_get_data_size(struct vfio_device *vdev,
+				 unsigned long *stop_copy_length)
+{
+	return -EOPNOTSUPP;
+}
+
+static const struct vfio_migration_ops vfio_ap_migration_ops = {
+	.migration_set_state = vfio_ap_set_state,
+	.migration_get_state = vfio_ap_get_state,
+	.migration_get_data_size = vfio_ap_get_data_size,
+};
+
+/**
+ * vfio_ap_init_migrations_capabilities - initialize migration capabilities
+ *
+ * @matrix_mdev: pointer to object containing the mdev state
+ */
+void vfio_ap_init_migration_capabilities(struct ap_matrix_mdev *matrix_mdev)
+{
+	if (ap_is_se_guest())
+		return;
+
+	matrix_mdev->vdev.migration_flags = VFIO_MIGRATION_STOP_COPY;
+	matrix_mdev->vdev.mig_ops = &vfio_ap_migration_ops;
+}
+
+/**
+ * vfio_ap_init_migration_data - initialize migration data and functions
+ *
+ * @matrix_mdev: pointer to object containing the mdev state
+ *
+ * Return: zero if initialization is successful; otherwise, returns a error.
+ */
+int vfio_ap_init_migration_data(struct ap_matrix_mdev *matrix_mdev)
+{
+	struct vfio_ap_migration_data *mig_data;
+
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	mig_data = kzalloc_obj(struct vfio_ap_migration_data, GFP_KERNEL);
+	if (!mig_data)
+		return -ENOMEM;
+
+	mig_data->mig_state = VFIO_DEVICE_STATE_RUNNING;
+	matrix_mdev->mig_data = mig_data;
+
+	return 0;
+}
+
+/**
+ * vfio_ap_release_migration_data: reclaim private migration data
+ *
+ * @vdev: pointer to the mdev
+ */
+void vfio_ap_release_migration_data(struct ap_matrix_mdev *matrix_mdev)
+{
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	if (!matrix_mdev->mig_data)
+		return;
+
+	kfree(matrix_mdev->mig_data->resuming_mig_file.ap_config);
+	kfree(matrix_mdev->mig_data->stop_copy_mig_file.ap_config);
+	kfree(matrix_mdev->mig_data);
+	matrix_mdev->mig_data = NULL;
+}
diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 36786d70a88f..90b0fce0123b 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -775,18 +775,30 @@ static bool vfio_ap_mdev_filter_matrix(struct ap_matrix_mdev *matrix_mdev,
 
 static int vfio_ap_mdev_init_dev(struct vfio_device *vdev)
 {
-	struct ap_matrix_mdev *matrix_mdev =
-		container_of(vdev, struct ap_matrix_mdev, vdev);
+	struct ap_matrix_mdev *matrix_mdev;
 
+	mutex_lock(&matrix_dev->mdevs_lock);
+	matrix_mdev = container_of(vdev, struct ap_matrix_mdev, vdev);
 	matrix_mdev->mdev = to_mdev_device(vdev->dev);
 	vfio_ap_matrix_init(&matrix_dev->info, &matrix_mdev->matrix);
 	matrix_mdev->pqap_hook = handle_pqap;
 	vfio_ap_matrix_init(&matrix_dev->info, &matrix_mdev->shadow_apcb);
 	hash_init(matrix_mdev->qtable.queues);
+	mutex_unlock(&matrix_dev->mdevs_lock);
 
 	return 0;
 }
 
+static void vfio_ap_mdev_release_dev(struct vfio_device *vdev)
+{
+	struct ap_matrix_mdev *matrix_mdev;
+
+	mutex_lock(&matrix_dev->mdevs_lock);
+	matrix_mdev = container_of(vdev, struct ap_matrix_mdev, vdev);
+	vfio_ap_release_migration_data(matrix_mdev);
+	mutex_unlock(&matrix_dev->mdevs_lock);
+}
+
 static int vfio_ap_mdev_probe(struct mdev_device *mdev)
 {
 	struct ap_matrix_mdev *matrix_mdev;
@@ -797,13 +809,28 @@ static int vfio_ap_mdev_probe(struct mdev_device *mdev)
 	if (IS_ERR(matrix_mdev))
 		return PTR_ERR(matrix_mdev);
 
+	/*
+	 * Migration capabilities must be initialized before calling
+	 * vfio_register_emulated_iommu_dev; otherwise, the VFIO core
+	 * will see mig_ops as NULL during the registration. This could
+	 * prevent the VFIO core from properly setting up migration
+	 * infrastructure like debugfs entries.
+	 *
+	 * This must be done before acquiring mdevs_lock to avoid an ABBA
+	 * deadlock: vfio_register_emulated_iommu_dev() acquires dev_set->lock
+	 * internally, while vfio_ap_mdev_open_device() is called by the VFIO
+	 * core with dev_set->lock already held and then acquires mdevs_lock.
+	 */
+	vfio_ap_init_migration_capabilities(matrix_mdev);
+
 	ret = vfio_register_emulated_iommu_dev(&matrix_mdev->vdev);
 	if (ret)
 		goto err_put_vdev;
+
+	mutex_lock(&matrix_dev->mdevs_lock);
 	matrix_mdev->req_trigger = NULL;
 	matrix_mdev->cfg_chg_trigger = NULL;
 	dev_set_drvdata(&mdev->dev, matrix_mdev);
-	mutex_lock(&matrix_dev->mdevs_lock);
 	list_add(&matrix_mdev->node, &matrix_dev->mdev_list);
 	mutex_unlock(&matrix_dev->mdevs_lock);
 	return 0;
@@ -2052,19 +2079,39 @@ static int vfio_ap_mdev_reset_qlist(struct list_head *qlist)
 
 static int vfio_ap_mdev_open_device(struct vfio_device *vdev)
 {
-	struct ap_matrix_mdev *matrix_mdev =
-		container_of(vdev, struct ap_matrix_mdev, vdev);
+	struct ap_matrix_mdev *matrix_mdev;
+	int ret;
 
 	if (!vdev->kvm)
 		return -EINVAL;
 
-	return vfio_ap_mdev_set_kvm(matrix_mdev, vdev->kvm);
+	mutex_lock(&matrix_dev->mdevs_lock);
+	matrix_mdev = container_of(vdev, struct ap_matrix_mdev, vdev);
+	ret = vfio_ap_init_migration_data(matrix_mdev);
+	mutex_unlock(&matrix_dev->mdevs_lock);
+
+	if (ret)
+		return ret;
+
+	ret = vfio_ap_mdev_set_kvm(matrix_mdev, vdev->kvm);
+	if (ret) {
+		/* Clean up migration data on failure */
+		mutex_lock(&matrix_dev->mdevs_lock);
+		vfio_ap_release_migration_data(matrix_mdev);
+		mutex_unlock(&matrix_dev->mdevs_lock);
+	}
+
+	return ret;
 }
 
 static void vfio_ap_mdev_close_device(struct vfio_device *vdev)
 {
-	struct ap_matrix_mdev *matrix_mdev =
-		container_of(vdev, struct ap_matrix_mdev, vdev);
+	struct ap_matrix_mdev *matrix_mdev;
+
+	mutex_lock(&matrix_dev->mdevs_lock);
+	matrix_mdev = container_of(vdev, struct ap_matrix_mdev, vdev);
+	vfio_ap_release_migration_data(matrix_mdev);
+	mutex_unlock(&matrix_dev->mdevs_lock);
 
 	vfio_ap_mdev_unset_kvm(matrix_mdev);
 }
@@ -2368,6 +2415,7 @@ static const struct attribute_group vfio_queue_attr_group = {
 
 static const struct vfio_device_ops vfio_ap_matrix_dev_ops = {
 	.init = vfio_ap_mdev_init_dev,
+	.release = vfio_ap_mdev_release_dev,
 	.open_device = vfio_ap_mdev_open_device,
 	.close_device = vfio_ap_mdev_close_device,
 	.ioctl = vfio_ap_mdev_ioctl,
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index 2b542648964b..a2a713f93674 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -172,4 +172,8 @@ void vfio_ap_on_cfg_changed(struct ap_config_info *new_config_info,
 void vfio_ap_on_scan_complete(struct ap_config_info *new_config_info,
 			      struct ap_config_info *old_config_info);
 
+void vfio_ap_init_migration_capabilities(struct ap_matrix_mdev *matrix_mdev);
+int vfio_ap_init_migration_data(struct ap_matrix_mdev *matrix_mdev);
+void vfio_ap_release_migration_data(struct ap_matrix_mdev *matrix_mdev);
+
 #endif /* _VFIO_AP_PRIVATE_H_ */
-- 
2.53.0

[PATCH v6 04/15] s390/vfio-ap: Reset migration state in VFIO_DEVICE_RESET ioctl handler

[Anthony Krowiak]

According to the VFIO migration specifications, userspace must issue a
VFIO_DEVICE_RESET ioctl if a vfio device enters an error state or fails a
state transition to recover the device and return its migration state to
RUNNING. This patch adds a function that is called when a VFIO_DEVICE_RESET
is issued that releases the migration files and frees the storage allocated
for maintaining the migration state.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_migration.c | 54 +++++++++++++++++++++++++
 drivers/s390/crypto/vfio_ap_ops.c       |  4 ++
 drivers/s390/crypto/vfio_ap_private.h   |  1 +
 3 files changed, 59 insertions(+)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index ae0bd1f415fe..093219e6bb9f 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -150,3 +150,57 @@ void vfio_ap_release_migration_data(struct ap_matrix_mdev *matrix_mdev)
 	kfree(matrix_mdev->mig_data);
 	matrix_mdev->mig_data = NULL;
 }
+
+static void vfio_ap_release_mig_files(struct ap_matrix_mdev *matrix_mdev)
+{
+	struct vfio_ap_migration_data *mig_data;
+
+	/*
+	 * The fput call does not call .release synchronously while the
+	 * mdevs_lock mutex is held, so there is no problem with incurring a
+	 * deadlock situation if fput is executed in this function.
+	 */
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	mig_data = matrix_mdev->mig_data;
+	if (!mig_data)
+		return;
+
+	if (mig_data->stop_copy_mig_file.filp) {
+		fput(mig_data->stop_copy_mig_file.filp);
+		mig_data->stop_copy_mig_file.filp = NULL;
+	}
+
+	kfree(mig_data->stop_copy_mig_file.ap_config);
+	mig_data->stop_copy_mig_file.ap_config = NULL;
+	mig_data->stop_copy_mig_file.config_sz = 0;
+
+	if (mig_data->resuming_mig_file.filp) {
+		fput(mig_data->resuming_mig_file.filp);
+		mig_data->resuming_mig_file.filp = NULL;
+	}
+
+	kfree(mig_data->resuming_mig_file.ap_config);
+	mig_data->resuming_mig_file.ap_config = NULL;
+	mig_data->resuming_mig_file.config_sz = 0;
+}
+
+/**
+ * vfio_ap_reset_migration_state - Reset the vfio-ap migration state
+ *
+ * @matrix_mdev: pointer to the object maintaining the vfio-ap device state
+ *
+ * Called during VFIO_DEVICE_RESET to clean up any active migration
+ * state and reset the device to RUNNING state as required by the VFIO
+ * migration specification.
+ */
+void vfio_ap_reset_migration_state(struct ap_matrix_mdev *matrix_mdev)
+{
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	if (!matrix_mdev->mig_data)
+		return;
+
+	vfio_ap_release_mig_files(matrix_mdev);
+	matrix_mdev->mig_data->mig_state = VFIO_DEVICE_STATE_RUNNING;
+}
diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 90b0fce0123b..d05372b50d2f 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -2330,6 +2330,10 @@ static ssize_t vfio_ap_mdev_ioctl(struct vfio_device *vdev,
 		break;
 	case VFIO_DEVICE_RESET:
 		ret = vfio_ap_mdev_reset_queues(matrix_mdev);
+		if (ret == 0) {
+			/* Reset migration state per VFIO migration spec */
+			vfio_ap_reset_migration_state(matrix_mdev);
+		}
 		break;
 	case VFIO_DEVICE_GET_IRQ_INFO:
 		ret = vfio_ap_get_irq_info(arg);
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index a2a713f93674..1fbdfcce5a11 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -175,5 +175,6 @@ void vfio_ap_on_scan_complete(struct ap_config_info *new_config_info,
 void vfio_ap_init_migration_capabilities(struct ap_matrix_mdev *matrix_mdev);
 int vfio_ap_init_migration_data(struct ap_matrix_mdev *matrix_mdev);
 void vfio_ap_release_migration_data(struct ap_matrix_mdev *matrix_mdev);
+void vfio_ap_reset_migration_state(struct ap_matrix_mdev *matrix_mdev);
 
 #endif /* _VFIO_AP_PRIVATE_H_ */
-- 
2.53.0

[PATCH v6 05/15] s390-vfio-ap: Callback to get/set vfio device mig state during guest migration

[Anthony Krowiak]

Implements two callbacks related to the current state of a vfio-ap device:
* The callback that sets a new migration state of a vfio-ap device during
  live migration of guests with pass-through access to AP devices. This
  callback is mandatory for VFIO_DEVICE_FEATURE_MIGRATION support.

  The function pointer for this callback is specified via the
  'migration_set_state' field of the 'vfio_migration_ops' structure
  which is stored with the VFIO device when the 'vfio_device'
  structure representing the mediated device is initialized.

* The callback that returns the current vfio device migration state during
  live migration of guests with pass-through access to AP devices.

  The function pointer for this callback is specified via the
  'migration_get_state' field of the 'vfio_migration_ops' structure
  which is stored with the VFIO device when the 'vfio_device'
  structure representing the mediated device is initialized.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_migration.c | 130 +++++++++++++++++++++++-
 1 file changed, 128 insertions(+), 2 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index 093219e6bb9f..77d15c5cc9af 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -72,16 +72,141 @@ struct vfio_ap_config {
 	struct vfio_ap_queue_info	qinfo[] __counted_by(num_queues);
 };
 
+static struct file *
+vfio_ap_transition_to_state(struct ap_matrix_mdev *matrix_mdev,
+			    enum vfio_device_mig_state new_state)
+{
+	struct vfio_ap_migration_data *mig_data;
+	enum vfio_device_mig_state cur_state;
+
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+	mig_data = matrix_mdev->mig_data;
+	cur_state = mig_data->mig_state;
+	dev_dbg(matrix_mdev->vdev.dev, "%s: %d -> %d\n", __func__, cur_state,
+		new_state);
+
+	if (cur_state == VFIO_DEVICE_STATE_STOP &&
+	    new_state == VFIO_DEVICE_STATE_STOP_COPY) {
+		/* TODO */
+		return ERR_PTR(-EOPNOTSUPP);
+	}
+
+	if (cur_state == VFIO_DEVICE_STATE_STOP &&
+	    new_state == VFIO_DEVICE_STATE_RESUMING) {
+		/* TODO */
+		return ERR_PTR(-EOPNOTSUPP);
+	}
+
+	if ((cur_state == VFIO_DEVICE_STATE_RESUMING &&
+	     new_state == VFIO_DEVICE_STATE_STOP) ||
+	    (cur_state == VFIO_DEVICE_STATE_STOP_COPY &&
+	     new_state == VFIO_DEVICE_STATE_STOP)) {
+		/* TODO */
+		return ERR_PTR(-EOPNOTSUPP);
+	}
+
+	if ((cur_state == VFIO_DEVICE_STATE_STOP &&
+	     new_state == VFIO_DEVICE_STATE_RUNNING) ||
+	    (cur_state == VFIO_DEVICE_STATE_RUNNING &&
+	     new_state == VFIO_DEVICE_STATE_STOP)) {
+		/* TODO */
+		return ERR_PTR(-EOPNOTSUPP);
+	}
+
+	/* vfio_mig_get_next_state() does not use arcs other than the above */
+	WARN_ON(true);
+
+	return ERR_PTR(-EINVAL);
+}
+
 static struct file *vfio_ap_set_state(struct vfio_device *vdev,
 				      enum vfio_device_mig_state  new_state)
 {
-	return NULL;
+	int ret;
+	struct file *filp = NULL;
+	struct ap_matrix_mdev *matrix_mdev;
+	enum vfio_device_mig_state next_state;
+	struct vfio_ap_migration_data *mig_data;
+
+	matrix_mdev = container_of(vdev, struct ap_matrix_mdev, vdev);
+
+	mutex_lock(&matrix_dev->mdevs_lock);
+	if (ap_is_se_guest()) {
+		dev_err_once(matrix_mdev->vdev.dev,
+			     "Migration not allowed from or to a Secure Execution guest\n");
+		mutex_unlock(&matrix_dev->mdevs_lock);
+		return ERR_PTR(-EPERM);
+	}
+
+	mig_data = matrix_mdev->mig_data;
+
+	/*
+	 * The mig_data pointer is set in the vfio_ap_init_migration_data
+	 * function which is called when the vfio-ap device fd is opened.
+	 * Since the implicit pre-open state is RUNNING, a request to set
+	 * RUNNING is a no-op. Any other state transition is invalid before
+	 * open_device.
+	 */
+	if (!mig_data) {
+		mutex_unlock(&matrix_dev->mdevs_lock);
+		if (new_state == VFIO_DEVICE_STATE_RUNNING)
+			return NULL;
+		return ERR_PTR(-ENODEV);
+	}
+
+	dev_dbg(vdev->dev, "%s -> %d\n", __func__, new_state);
+
+	while (mig_data->mig_state != VFIO_DEVICE_STATE_ERROR &&
+	       mig_data->mig_state != new_state) {
+		ret = vfio_mig_get_next_state(vdev, mig_data->mig_state,
+					      new_state, &next_state);
+		if (ret) {
+			filp = ERR_PTR(ret);
+			break;
+		}
+
+		filp = vfio_ap_transition_to_state(matrix_mdev, next_state);
+		if (IS_ERR(filp))
+			break;
+
+		mig_data->mig_state = next_state;
+
+		if (WARN_ON(filp && new_state != next_state)) {
+			fput(filp);
+			filp = ERR_PTR(-EINVAL);
+			break;
+		}
+	}
+
+	mutex_unlock(&matrix_dev->mdevs_lock);
+
+	return filp;
 }
 
 static int vfio_ap_get_state(struct vfio_device *vdev,
 			     enum vfio_device_mig_state  *current_state)
 {
-	return -EOPNOTSUPP;
+	struct ap_matrix_mdev *matrix_mdev;
+	struct vfio_ap_migration_data *mig_data;
+
+	mutex_lock(&matrix_dev->mdevs_lock);
+
+	matrix_mdev = container_of(vdev, struct ap_matrix_mdev, vdev);
+	mig_data =  matrix_mdev->mig_data;
+
+	/*
+	 * The mig_data pointer is set in the vfio_ap_init_migration_data
+	 * function which is called when the vfio-ap device fd is opened.
+	 * If mig_data is NULL, report RUNNING as the implicit pre-open state
+	 * so userspace doesn't need to perform any state transition before the
+	 * device becomes active.
+	 */
+	*current_state = (mig_data) ? mig_data->mig_state :
+				      VFIO_DEVICE_STATE_RUNNING;
+
+	mutex_unlock(&matrix_dev->mdevs_lock);
+
+	return 0;
 }
 
 static int vfio_ap_get_data_size(struct vfio_device *vdev,
@@ -103,6 +228,7 @@ static const struct vfio_migration_ops vfio_ap_migration_ops = {
  */
 void vfio_ap_init_migration_capabilities(struct ap_matrix_mdev *matrix_mdev)
 {
+	/* Live guest migration is not supported for SE guests */
 	if (ap_is_se_guest())
 		return;
 
-- 
2.53.0

[PATCH v6 06/15] s390/vfio-ap: Transition guest migration state from STOP to STOP_COPY

[Anthony Krowiak]

The transition of the guest migration state from VFIO_DEVICE_STATE_STOP to
VFIO_DEVICE_STATE_STOP_COPY begins the process of saving the
vfio device state. The vfio device state is comprised of the guest's
AP configuration which specifies the adapters, domains and control
domains to which the guest will be given access.

To begin the process of saving the vfio device state, the VFIO AP device
driver opens a file stream that will be used to read the source guest's
AP configuration.

Note:
This commit introduces the file operations structure for migration state
files with a stub implementation of the read operation. The complete
implementation is provided in the subsequent commit.

This incremental approach allows for easier review of the migration
infrastructure setup separate from the actual implementation logic.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_migration.c | 146 ++++++++++++++++++++----
 1 file changed, 126 insertions(+), 20 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index 77d15c5cc9af..2b736bab7729 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -4,6 +4,7 @@
  *
  * Copyright IBM Corp. 2025
  */
+#include <linux/anon_inodes.h>
 #include <linux/file.h>
 #include "vfio_ap_private.h"
 
@@ -72,6 +73,92 @@ struct vfio_ap_config {
 	struct vfio_ap_queue_info	qinfo[] __counted_by(num_queues);
 };
 
+static void
+vfio_ap_release_stop_copy_file(struct vfio_ap_migration_data *mig_data)
+{
+	kfree(mig_data->stop_copy_mig_file.ap_config);
+	mig_data->stop_copy_mig_file.ap_config = NULL;
+	mig_data->stop_copy_mig_file.config_sz = 0;
+	mig_data->stop_copy_mig_file.filp = NULL;
+}
+
+static ssize_t
+vfio_ap_stop_copy_read(struct file *, char __user *, size_t, loff_t *)
+{
+	/* TODO */
+	return -EOPNOTSUPP;
+}
+
+static int vfio_ap_release_mig_file(struct inode *file_inode, struct file *filp)
+{
+	struct ap_matrix_mdev *matrix_mdev = filp->private_data;
+	int ret = 0;
+
+	mutex_lock(&matrix_dev->mdevs_lock);
+
+	/*
+	 * mig_data may be NULL if the device was closed (vfio_ap_mdev_close_device)
+	 * before the migration FD was released by userspace. In that case the
+	 * migration file state was already cleaned up; nothing to do here.
+	 */
+	if (!matrix_mdev->mig_data)
+		goto done;
+
+	if (filp == matrix_mdev->mig_data->stop_copy_mig_file.filp)
+		vfio_ap_release_stop_copy_file(matrix_mdev->mig_data);
+	else
+		ret = -ENOENT;
+
+done:
+	mutex_unlock(&matrix_dev->mdevs_lock);
+	vfio_device_put_registration(&matrix_mdev->vdev);
+	return ret;
+}
+
+static const struct file_operations vfio_ap_stop_copy_fops = {
+	.owner = THIS_MODULE,
+	.read = vfio_ap_stop_copy_read,
+	.compat_ioctl = compat_ptr_ioctl,
+	.release = vfio_ap_release_mig_file,
+};
+
+static struct file *vfio_ap_open_file_stream(struct ap_matrix_mdev *matrix_mdev,
+					     const struct file_operations *fops,
+					     int flags)
+{
+	struct file *filp;
+
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	/*
+	 * Pin the vfio_device registration so that matrix_mdev cannot be freed
+	 * while the migration FD is still open. The matching put is in
+	 * vfio_ap_release_mig_file().
+	 */
+	if (!vfio_device_try_get_registration(&matrix_mdev->vdev))
+		return ERR_PTR(-ENODEV);
+
+	filp = anon_inode_getfile("vfio_ap_mig_file", fops, matrix_mdev, flags);
+	if (IS_ERR(filp)) {
+		vfio_device_put_registration(&matrix_mdev->vdev);
+		return filp;
+	}
+
+	stream_open(filp->f_inode, filp);
+
+	/*
+	 * Take a second reference on the file so the driver holds its own
+	 * reference independent of the one consumed when the VFIO core
+	 * installs the FD into the userspace file table. Without this,
+	 * the driver's saved filp could be the only reference; an fput()
+	 * during a device reset would prematurely destroy the file while
+	 * the userspace FD still points to it.
+	 */
+	get_file(filp);
+
+	return filp;
+}
+
 static struct file *
 vfio_ap_transition_to_state(struct ap_matrix_mdev *matrix_mdev,
 			    enum vfio_device_mig_state new_state)
@@ -85,10 +172,22 @@ vfio_ap_transition_to_state(struct ap_matrix_mdev *matrix_mdev,
 	dev_dbg(matrix_mdev->vdev.dev, "%s: %d -> %d\n", __func__, cur_state,
 		new_state);
 
+	/*
+	 * Begins the process of saving the vfio device state by creating and
+	 * returning a streaming data_fd to be used to read out the internal
+	 * state of the vfio-ap device on the source host.
+	 */
 	if (cur_state == VFIO_DEVICE_STATE_STOP &&
 	    new_state == VFIO_DEVICE_STATE_STOP_COPY) {
-		/* TODO */
-		return ERR_PTR(-EOPNOTSUPP);
+		struct file *filp = vfio_ap_open_file_stream(matrix_mdev,
+							     &vfio_ap_stop_copy_fops,
+							     O_RDONLY);
+		if (IS_ERR(filp))
+			return ERR_CAST(filp);
+
+		mig_data->stop_copy_mig_file.filp = filp;
+
+		return filp;
 	}
 
 	if (cur_state == VFIO_DEVICE_STATE_STOP &&
@@ -259,24 +358,6 @@ int vfio_ap_init_migration_data(struct ap_matrix_mdev *matrix_mdev)
 	return 0;
 }
 
-/**
- * vfio_ap_release_migration_data: reclaim private migration data
- *
- * @vdev: pointer to the mdev
- */
-void vfio_ap_release_migration_data(struct ap_matrix_mdev *matrix_mdev)
-{
-	lockdep_assert_held(&matrix_dev->mdevs_lock);
-
-	if (!matrix_mdev->mig_data)
-		return;
-
-	kfree(matrix_mdev->mig_data->resuming_mig_file.ap_config);
-	kfree(matrix_mdev->mig_data->stop_copy_mig_file.ap_config);
-	kfree(matrix_mdev->mig_data);
-	matrix_mdev->mig_data = NULL;
-}
-
 static void vfio_ap_release_mig_files(struct ap_matrix_mdev *matrix_mdev)
 {
 	struct vfio_ap_migration_data *mig_data;
@@ -311,6 +392,31 @@ static void vfio_ap_release_mig_files(struct ap_matrix_mdev *matrix_mdev)
 	mig_data->resuming_mig_file.config_sz = 0;
 }
 
+/**
+ * vfio_ap_release_migration_data: reclaim private migration data
+ *
+ * @vdev: pointer to the mdev
+ */
+void vfio_ap_release_migration_data(struct ap_matrix_mdev *matrix_mdev)
+{
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	if (!matrix_mdev->mig_data)
+		return;
+
+	/*
+	 * Drop the driver's get_file() references on any open migration FDs
+	 * and free the associated ap_config buffers before freeing mig_data.
+	 * This ensures that if the device is closed while a migration FD is
+	 * still held by userspace, vfio_ap_release_mig_file() will see
+	 * mig_data == NULL and skip the cleanup (the fput() here will
+	 * eventually trigger .release, but mig_data is gone by then).
+	 */
+	vfio_ap_release_mig_files(matrix_mdev);
+	kfree(matrix_mdev->mig_data);
+	matrix_mdev->mig_data = NULL;
+}
+
 /**
  * vfio_ap_reset_migration_state - Reset the vfio-ap migration state
  *
-- 
2.53.0

[PATCH v6 07/15] s390/vfio-ap: File ops called to save the vfio device migration state

[Anthony Krowiak]

Implements the read callback function that was added to the
file_operations structure for the file created to save the state of the
vfio-ap device when the migration state transitioned from STOP to
to the STOP_COPY state.

This function copies the guest's AP configuration information to
userspace. The information copied is comprised of the APQN of each queue
device passed through to the guest along with its hardware information.
This state data will be transferred to the vfio_ap device driver on the
destination host when the state is transitioned to RESUMING.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_migration.c | 255 +++++++++++++++++++++++-
 1 file changed, 248 insertions(+), 7 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index 2b736bab7729..e4bc67b1eb84 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -82,13 +82,6 @@ vfio_ap_release_stop_copy_file(struct vfio_ap_migration_data *mig_data)
 	mig_data->stop_copy_mig_file.filp = NULL;
 }
 
-static ssize_t
-vfio_ap_stop_copy_read(struct file *, char __user *, size_t, loff_t *)
-{
-	/* TODO */
-	return -EOPNOTSUPP;
-}
-
 static int vfio_ap_release_mig_file(struct inode *file_inode, struct file *filp)
 {
 	struct ap_matrix_mdev *matrix_mdev = filp->private_data;
@@ -115,6 +108,254 @@ static int vfio_ap_release_mig_file(struct inode *file_inode, struct file *filp)
 	return ret;
 }
 
+/**
+ * validate_stop_copy_read_parms: Validate the input parameters to the
+ *                                vfio_ap_stop_copy_read function
+ *
+ * @matrix_mdev: The object device containing the state to be read
+ * @filp: Pointer to the file stream used to read the vfio-ap device state
+ * @pos:  The file offset from which to start reading data
+ * @len:  The length of the data to be read
+ *
+ * Verify the following:
+ * - @filp private data is an ap_matrix_mdev instance
+ * - @filp is the instance opened when state transitioned from STOP to STOP_COPY
+ * - @pos + @len does not cause integer overflow
+ *
+ * Returns: 0 if the parameters pass validation; otherwise returns an error
+ */
+static int validate_stop_copy_read_parms(struct file *filp, loff_t *pos,
+					 size_t len)
+{
+	struct vfio_ap_migration_data *mig_data;
+	struct ap_matrix_mdev *matrix_mdev;
+	loff_t total_len;
+
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	if (check_add_overflow((loff_t)len, *pos, &total_len))
+		return -EIO;
+
+	/*
+	 * matrix_mdev is guaranteed live here: vfio_ap_open_file_stream() took
+	 * a vfio_device registration reference that is held until
+	 * vfio_ap_release_mig_file() runs, so the embedding matrix_mdev cannot
+	 * be freed while this file descriptor is open.
+	 */
+	matrix_mdev = filp->private_data;
+
+	if (!matrix_mdev->mig_data)
+		return -ENODEV;
+
+	mig_data = matrix_mdev->mig_data;
+
+	if (mig_data->stop_copy_mig_file.filp != filp)
+		return -EINVAL;
+
+	return 0;
+}
+
+static size_t vfio_ap_config_size(struct ap_matrix_mdev *matrix_mdev,
+				  int *num_queues)
+{
+	size_t qinfo_size;
+
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	*num_queues = vfio_ap_mdev_get_num_queues(&matrix_mdev->shadow_apcb);
+	qinfo_size = *num_queues * sizeof(struct vfio_ap_queue_info);
+
+	return qinfo_size + sizeof(struct vfio_ap_config);
+}
+
+static int get_hardware_info_for_queue(const char *mdev_name,
+				       struct ap_tapq_hwinfo *hwinfo,
+				       unsigned long apqn)
+{
+	struct ap_queue_status status;
+
+	status = ap_tapq(apqn, hwinfo);
+
+	switch (status.response_code) {
+	case AP_RESPONSE_NORMAL:
+	case AP_RESPONSE_RESET_IN_PROGRESS:
+	case AP_RESPONSE_DECONFIGURED:
+	case AP_RESPONSE_CHECKSTOPPED:
+	case AP_RESPONSE_BUSY:
+		/* For all these RCs the tapq info should be available */
+		return 0;
+	case AP_RESPONSE_Q_NOT_AVAIL:
+		pr_err("vfio_ap_mdev %s: Failed to get hwinfo for queue %02lx.%04lx: TAPQ rc=%d",
+		       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn),
+		       status.response_code);
+		return -ENODEV;
+	default:
+		/*
+		 * Without a pending async error, the tapq info should be
+		 * available
+		 */
+		if (status.async)
+			return 0;
+
+		pr_err("vfio_ap_mdev %s:Failed to get hwinfo for queue %02lx.%04lx: TAPQ rc=%d",
+		       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn),
+		       status.response_code);
+		return -EIO;
+	}
+
+	return -EINVAL;
+}
+
+static int vfio_ap_store_queue_info(const char *mdev_name,
+				    struct vfio_ap_config *ap_config)
+{
+	struct ap_tapq_hwinfo source_hwinfo;
+	unsigned long num_queues;
+	int ret;
+
+	/*
+	 * ap_tapq() is a hardware instruction that may take time to complete.
+	 * It must be called without mdevs_lock held to avoid blocking other
+	 * mdevs. The apqn list was already snapshotted into ap_config->qinfo[]
+	 * by the caller under the lock.
+	 */
+	for (num_queues = 0; num_queues < ap_config->num_queues; num_queues++) {
+		ret = get_hardware_info_for_queue(mdev_name, &source_hwinfo,
+						  ap_config->qinfo[num_queues].apqn);
+		if (ret)
+			return ret;
+
+		ap_config->qinfo[num_queues].data = source_hwinfo.value;
+	}
+
+	return 0;
+}
+
+static int vfio_ap_get_config(struct ap_matrix_mdev *matrix_mdev)
+{
+	unsigned long *apm, *aqm, apid, apqi, num_queues;
+	struct vfio_ap_config *ap_configuration;
+	const char *mdev_name;
+	size_t ap_config_size;
+	int ret;
+
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	ap_config_size = vfio_ap_config_size(matrix_mdev, (int *)&num_queues);
+
+	ap_configuration = kzalloc(ap_config_size, GFP_KERNEL_ACCOUNT);
+	if (!ap_configuration)
+		return -ENOMEM;
+
+	/*
+	 * num_queues must be set before writing qinfo[] elements; the
+	 * __counted_by(num_queues) annotation on qinfo[] causes the compiler to
+	 * insert bounds checks that evaluate against ap_configuration->num_queues.
+	 * Writing through qinfo[i] with num_queues still 0 would trap.
+	 */
+	ap_configuration->num_queues = num_queues;
+
+	apm = matrix_mdev->shadow_apcb.apm;
+	aqm = matrix_mdev->shadow_apcb.aqm;
+	num_queues = 0;
+	for_each_set_bit_inv(apid, apm, AP_DEVICES) {
+		for_each_set_bit_inv(apqi, aqm, AP_DOMAINS) {
+			ap_configuration->qinfo[num_queues].apqn =
+				AP_MKQID(apid, apqi);
+			num_queues += 1;
+		}
+	}
+	memcpy(ap_configuration->adm, matrix_mdev->shadow_apcb.adm,
+	       sizeof(ap_configuration->adm));
+	mdev_name = dev_name(matrix_mdev->vdev.dev);
+
+	ret = vfio_ap_store_queue_info(mdev_name, ap_configuration);
+	if (ret) {
+		kfree(ap_configuration);
+		return ret;
+	}
+
+	matrix_mdev->mig_data->stop_copy_mig_file.ap_config = ap_configuration;
+	matrix_mdev->mig_data->stop_copy_mig_file.config_sz = ap_config_size;
+
+	return 0;
+}
+
+static ssize_t vfio_ap_stop_copy_read(struct file *filp, char __user *buf,
+				      size_t len, loff_t *pos)
+{
+	struct vfio_ap_migration_file *mig_file;
+	struct ap_matrix_mdev *matrix_mdev;
+	loff_t read_pos;
+	ssize_t ret;
+
+	/*
+	 * When userspace calls read() with an explicit offset (pread), pos is
+	 * non-NULL and the function rejects it with -ESPIPE (illegal seek). For
+	 * normal read() calls, pos is NULL, so we'll use the file's internal
+	 * position filp->f_pos
+	 */
+	if (pos)
+		return -ESPIPE;
+
+	mutex_lock(&matrix_dev->mdevs_lock);
+
+	pos = &filp->f_pos;
+
+	ret = validate_stop_copy_read_parms(filp, pos, len);
+	if (ret) {
+		mutex_unlock(&matrix_dev->mdevs_lock);
+		return ret;
+	}
+
+	matrix_mdev = filp->private_data;
+	mig_file = &matrix_mdev->mig_data->stop_copy_mig_file;
+
+	if (!mig_file->ap_config) {
+		ret = vfio_ap_get_config(matrix_mdev);
+		if (ret) {
+			mutex_unlock(&matrix_dev->mdevs_lock);
+			return ret;
+		}
+	}
+
+	/*
+	 * Compute the offset and clamped length fully under the lock so that
+	 * concurrent read()s on this stream file each see a consistent view of
+	 * the current position.  *pos is advanced here while we still hold the
+	 * lock; copy_to_user() then uses the snapshot read_pos.  This prevents
+	 * two threads from calculating the same offset and both copying the
+	 * same region (or one reading past the end of the buffer).
+	 */
+	if (*pos >= mig_file->config_sz) {
+		mutex_unlock(&matrix_dev->mdevs_lock);
+		return 0;
+	}
+
+	len = min_t(size_t, mig_file->config_sz - *pos, len);
+	if (len == 0) {
+		mutex_unlock(&matrix_dev->mdevs_lock);
+		return 0;
+	}
+
+	read_pos = *pos;
+	*pos += len;
+
+	/*
+	 * Drop the lock only for the copy_to_user().  The ap_config buffer is
+	 * stable: it is allocated once in vfio_ap_get_config() and freed only
+	 * in vfio_ap_release_mig_files() / vfio_ap_release_stop_copy_file(),
+	 * both of which require mdevs_lock.  Since we already advanced *pos
+	 * above, no other thread will compute an overlapping region.
+	 */
+	mutex_unlock(&matrix_dev->mdevs_lock);
+
+	if (copy_to_user(buf, (char *)mig_file->ap_config + read_pos, len))
+		return -EFAULT;
+
+	return len;
+}
+
 static const struct file_operations vfio_ap_stop_copy_fops = {
 	.owner = THIS_MODULE,
 	.read = vfio_ap_stop_copy_read,
-- 
2.53.0

[PATCH v6 08/15] s390/vfio-ap: Transition device migration state from STOP to RESUMING

[Anthony Krowiak]

Transitioning from VFIO_DEVICE_STATE_STOP to VFIO_DEVICE_STATE_RESUMING
starts a process of restoring the device state of the vfio device on the
target system. To prepare for restoring the device state, open a file
stream to receive the guest's AP configuration saved when the device state
on the source system transitioned from VFIO_DEVICE_STATE_STOP to
VFIO_DEVICE_STATE_STOP_COPY.

Note:
This commit introduces the file operations structure for migration state
files with a stub implementation of the write operation. The complete
implementation is provided in the subsequent commit.

This incremental approach allows for easier review of the migration
infrastructure setup separate from the actual implementation logic.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_migration.c | 45 +++++++++++++++++++++++--
 1 file changed, 43 insertions(+), 2 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index e4bc67b1eb84..c7fecad0b676 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -82,6 +82,15 @@ vfio_ap_release_stop_copy_file(struct vfio_ap_migration_data *mig_data)
 	mig_data->stop_copy_mig_file.filp = NULL;
 }
 
+static void
+vfio_ap_release_resuming_file(struct vfio_ap_migration_data *mig_data)
+{
+	kfree(mig_data->resuming_mig_file.ap_config);
+	mig_data->resuming_mig_file.ap_config = NULL;
+	mig_data->resuming_mig_file.config_sz = 0;
+	mig_data->resuming_mig_file.filp = NULL;
+}
+
 static int vfio_ap_release_mig_file(struct inode *file_inode, struct file *filp)
 {
 	struct ap_matrix_mdev *matrix_mdev = filp->private_data;
@@ -99,6 +108,8 @@ static int vfio_ap_release_mig_file(struct inode *file_inode, struct file *filp)
 
 	if (filp == matrix_mdev->mig_data->stop_copy_mig_file.filp)
 		vfio_ap_release_stop_copy_file(matrix_mdev->mig_data);
+	else if (filp == matrix_mdev->mig_data->resuming_mig_file.filp)
+		vfio_ap_release_resuming_file(matrix_mdev->mig_data);
 	else
 		ret = -ENOENT;
 
@@ -400,6 +411,26 @@ static struct file *vfio_ap_open_file_stream(struct ap_matrix_mdev *matrix_mdev,
 	return filp;
 }
 
+static ssize_t vfio_ap_resuming_write(struct file *filp, const char __user *buf,
+				      size_t len, loff_t *pos)
+{
+	/* TODO */
+	return -EOPNOTSUPP;
+}
+
+static const struct file_operations vfio_ap_resume_fops = {
+	.owner = THIS_MODULE,
+	.write = vfio_ap_resuming_write,
+	.release = vfio_ap_release_mig_file,
+};
+
+static struct file *vfio_ap_resuming_init(struct ap_matrix_mdev *matrix_mdev)
+{
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	return vfio_ap_open_file_stream(matrix_mdev, &vfio_ap_resume_fops, O_WRONLY);
+}
+
 static struct file *
 vfio_ap_transition_to_state(struct ap_matrix_mdev *matrix_mdev,
 			    enum vfio_device_mig_state new_state)
@@ -431,10 +462,20 @@ vfio_ap_transition_to_state(struct ap_matrix_mdev *matrix_mdev,
 		return filp;
 	}
 
+	/*
+	 * Begins the process of restoring the vfio device state by creating and
+	 * returning a streaming data_fd to be used to read in the internal
+	 * state of the vfio-ap device on the destination host.
+	 */
 	if (cur_state == VFIO_DEVICE_STATE_STOP &&
 	    new_state == VFIO_DEVICE_STATE_RESUMING) {
-		/* TODO */
-		return ERR_PTR(-EOPNOTSUPP);
+		struct file *filp = vfio_ap_resuming_init(matrix_mdev);
+
+		if (IS_ERR(filp))
+			return ERR_CAST(filp);
+
+		mig_data->resuming_mig_file.filp = filp;
+		return filp;
 	}
 
 	if ((cur_state == VFIO_DEVICE_STATE_RESUMING &&
-- 
2.53.0

[PATCH v6 09/15] s390/vfio-ap: Add method to set a new guest AP configuration

[Anthony Krowiak]

Adds a new vfio_ap_set_new_config function to set a guest's AP
configuration. This is needed in order to set the state of the mdev when
it is migrated from a remote host system during the RESUMING phase.

Key changes:
* Refactored code from the ap_config_store function - handles changes to
  the sysfs ap_config attribute - into a new, non-static function which
  is callable from the ap_config_store function as well as the live guest
  migration code.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_ops.c     | 225 ++++++++++++++------------
 drivers/s390/crypto/vfio_ap_private.h |  61 +++++++
 2 files changed, 187 insertions(+), 99 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index d05372b50d2f..0b49be22d5d8 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -81,53 +81,6 @@ static inline void release_update_locks_for_kvm(struct kvm *kvm)
 	mutex_unlock(&matrix_dev->guests_lock);
 }
 
-/**
- * get_update_locks_for_mdev: Acquire the locks required to dynamically update a
- *			      KVM guest's APCB in the proper order.
- *
- * @matrix_mdev: a pointer to a struct ap_matrix_mdev object containing the AP
- *		 configuration data to use to update a KVM guest's APCB.
- *
- * The proper locking order is:
- * 1. matrix_dev->guests_lock: required to use the KVM pointer to update a KVM
- *			       guest's APCB.
- * 2. matrix_mdev->kvm->lock:  required to update a guest's APCB
- * 3. matrix_dev->mdevs_lock:  required to access data stored in a matrix_mdev
- *
- * Note: If @matrix_mdev is NULL or is not attached to a KVM guest, the KVM
- *	 lock will not be taken.
- */
-static inline void get_update_locks_for_mdev(struct ap_matrix_mdev *matrix_mdev)
-{
-	mutex_lock(&matrix_dev->guests_lock);
-	if (matrix_mdev && matrix_mdev->kvm)
-		mutex_lock(&matrix_mdev->kvm->lock);
-	mutex_lock(&matrix_dev->mdevs_lock);
-}
-
-/**
- * release_update_locks_for_mdev: Release the locks used to dynamically update a
- *				  KVM guest's APCB in the proper order.
- *
- * @matrix_mdev: a pointer to a struct ap_matrix_mdev object containing the AP
- *		 configuration data to use to update a KVM guest's APCB.
- *
- * The proper unlocking order is:
- * 1. matrix_dev->mdevs_lock
- * 2. matrix_mdev->kvm->lock
- * 3. matrix_dev->guests_lock
- *
- * Note: If @matrix_mdev is NULL or is not attached to a KVM guest, the KVM
- *	 lock will not be released.
- */
-static inline void release_update_locks_for_mdev(struct ap_matrix_mdev *matrix_mdev)
-{
-	mutex_unlock(&matrix_dev->mdevs_lock);
-	if (matrix_mdev && matrix_mdev->kvm)
-		mutex_unlock(&matrix_mdev->kvm->lock);
-	mutex_unlock(&matrix_dev->guests_lock);
-}
-
 /**
  * get_update_locks_by_apqn: Find the mdev to which an APQN is assigned and
  *			     acquire the locks required to update the APCB of
@@ -642,8 +595,7 @@ static int handle_pqap(struct kvm_vcpu *vcpu)
 	return 0;
 }
 
-static void vfio_ap_matrix_init(struct ap_config_info *info,
-				struct ap_matrix *matrix)
+void vfio_ap_matrix_init(struct ap_config_info *info, struct ap_matrix *matrix)
 {
 	matrix->apm_max = info->apxa ? info->na : 63;
 	matrix->aqm_max = info->apxa ? info->nd : 15;
@@ -1018,19 +970,20 @@ static void vfio_ap_mdev_link_adapter(struct ap_matrix_mdev *matrix_mdev,
 	unsigned long apqi;
 
 	for_each_set_bit_inv(apqi, matrix_mdev->matrix.aqm, AP_DOMAINS)
-		vfio_ap_mdev_link_apqn(matrix_mdev,
-				       AP_MKQID(apid, apqi));
+		vfio_ap_mdev_link_apqn(matrix_mdev, AP_MKQID(apid, apqi));
 }
 
-static void collect_queues_to_reset(struct ap_matrix_mdev *matrix_mdev,
-				    unsigned long apid,
-				    struct list_head *qlist)
+static void collect_queues_by_apid(struct ap_matrix_mdev *matrix_mdev,
+				   unsigned long apid,
+				   struct list_head *qlist)
 {
 	struct vfio_ap_queue *q;
 	unsigned long  apqi;
 
 	for_each_set_bit_inv(apqi, matrix_mdev->shadow_apcb.aqm, AP_DOMAINS) {
-		q = vfio_ap_mdev_get_queue(matrix_mdev, AP_MKQID(apid, apqi));
+		q = matrix_mdev ?
+				vfio_ap_mdev_get_queue(matrix_mdev, AP_MKQID(apid, apqi)) :
+				vfio_ap_find_queue(AP_MKQID(apid, apqi));
 		if (q)
 			list_add_tail(&q->reset_qnode, qlist);
 	}
@@ -1042,7 +995,7 @@ static void reset_queues_for_apid(struct ap_matrix_mdev *matrix_mdev,
 	struct list_head qlist;
 
 	INIT_LIST_HEAD(&qlist);
-	collect_queues_to_reset(matrix_mdev, apid, &qlist);
+	collect_queues_by_apid(matrix_mdev, apid, &qlist);
 	vfio_ap_mdev_reset_qlist(&qlist);
 }
 
@@ -1058,7 +1011,7 @@ static int reset_queues_for_apids(struct ap_matrix_mdev *matrix_mdev,
 	INIT_LIST_HEAD(&qlist);
 
 	for_each_set_bit_inv(apid, apm_reset, AP_DEVICES)
-		collect_queues_to_reset(matrix_mdev, apid, &qlist);
+		collect_queues_by_apid(matrix_mdev, apid, &qlist);
 
 	return vfio_ap_mdev_reset_qlist(&qlist);
 }
@@ -1729,54 +1682,100 @@ static void ap_matrix_copy(struct ap_matrix *dst, struct ap_matrix *src)
 	bitmap_copy(dst->adm, src->adm, AP_DOMAINS);
 }
 
-static ssize_t ap_config_store(struct device *dev, struct device_attribute *attr,
-			       const char *buf, size_t count)
+static void get_removed_matrixes(struct ap_matrix *m_removed,
+				 struct ap_matrix *m_old,
+				 struct ap_matrix *m_new)
 {
-	struct ap_matrix_mdev *matrix_mdev = dev_get_drvdata(dev);
-	struct ap_matrix m_new, m_old, m_added, m_removed;
+	bitmap_andnot(m_removed->apm, m_old->apm, m_new->apm, AP_DEVICES);
+	bitmap_andnot(m_removed->aqm, m_old->aqm, m_new->aqm, AP_DOMAINS);
+	bitmap_andnot(m_removed->adm, m_old->adm, m_new->adm, AP_DOMAINS);
+}
+
+static void get_added_matrixes(struct ap_matrix *m_added,
+			       struct ap_matrix *m_old,
+			       struct ap_matrix *m_new)
+{
+	bitmap_andnot(m_added->apm, m_new->apm, m_old->apm, AP_DEVICES);
+	bitmap_andnot(m_added->aqm, m_new->aqm, m_old->aqm, AP_DOMAINS);
+	bitmap_andnot(m_added->adm, m_new->adm, m_old->adm, AP_DOMAINS);
+}
+
+static int validate_new_state(struct ap_matrix_mdev *matrix_mdev)
+{
+	int rc;
+
+	/* Ensure new state is valid, else undo new state */
+	rc = vfio_ap_mdev_validate_masks(matrix_mdev);
+	if (rc)
+		return rc;
+
+	rc = ap_matrix_overflow_check(matrix_mdev);
+	if (rc)
+		return rc;
+
+	return 0;
+}
+
+static void link_new_queues(struct ap_matrix_mdev *matrix_mdev,
+			    struct ap_matrix *m_added)
+{
+	unsigned long apid, apqi;
+
+	for_each_set_bit_inv(apid, m_added->apm, AP_DEVICES)
+		vfio_ap_mdev_link_adapter(matrix_mdev, apid);
+
+	for_each_set_bit_inv(apqi, m_added->aqm, AP_DOMAINS)
+		vfio_ap_mdev_link_domain(matrix_mdev, apqi);
+}
+
+/**
+ * vfio_ap_set_new_guest_config:
+ *
+ * Set a new AP configuration for a guest.
+ *
+ * @matrix_mdev: Object used to maintain the AP configuration for a guest
+ * @m_new:		 Object used to set the new AP configuration
+ *
+ * Returns: zero (0) if the new AP configuration is successfully set; otherwise,
+ *	    returns an error:
+ *
+ *	    ~ EADDRNOTAVAIL One or more APQNs are reserved for host use
+ *	    ~ EADDRINUSE    One or more APQNs are assigned to another mdev
+ *	    ~ ENODEV	    An adapter, domain or control domain in the new
+ *			    AP configuration exceeds the max architected value
+ */
+int vfio_ap_set_new_guest_config(struct ap_matrix_mdev *matrix_mdev,
+				 struct ap_matrix *m_new)
+{
+	struct ap_matrix m_old, m_old_shadow, m_added, m_removed;
 	DECLARE_BITMAP(apm_filtered, AP_DEVICES);
-	unsigned long newbit;
-	char *newbuf, *rest;
-	int rc = count;
 	bool do_update;
+	int rc;
 
-	newbuf = kstrndup(buf, AP_CONFIG_STRLEN, GFP_KERNEL);
-	if (!newbuf)
-		return -ENOMEM;
-	rest = newbuf;
+	lockdep_assert_held(&ap_attr_mutex);
+	assert_has_update_locks_for_mdev(matrix_mdev);
 
-	mutex_lock(&ap_attr_mutex);
-	get_update_locks_for_mdev(matrix_mdev);
-
-	/* Save old state */
+	/* Save the old state */
 	ap_matrix_copy(&m_old, &matrix_mdev->matrix);
-	if (parse_bitmap(&rest, m_new.apm, AP_DEVICES) ||
-	    parse_bitmap(&rest, m_new.aqm, AP_DOMAINS) ||
-	    parse_bitmap(&rest, m_new.adm, AP_DOMAINS)) {
-		rc = -EINVAL;
-		goto out;
-	}
+	ap_matrix_copy(&m_old_shadow, &matrix_mdev->shadow_apcb);
 
-	bitmap_andnot(m_removed.apm, m_old.apm, m_new.apm, AP_DEVICES);
-	bitmap_andnot(m_removed.aqm, m_old.aqm, m_new.aqm, AP_DOMAINS);
-	bitmap_andnot(m_added.apm, m_new.apm, m_old.apm, AP_DEVICES);
-	bitmap_andnot(m_added.aqm, m_new.aqm, m_old.aqm, AP_DOMAINS);
+	/*
+	 * Get the adapters, domains and control domains added and/or removed
+	 * from the existing configuration
+	 */
+	get_removed_matrixes(&m_removed, &m_old, m_new);
+	get_added_matrixes(&m_added, &m_old, m_new);
 
 	/* Need new bitmaps in matrix_mdev for validation */
-	ap_matrix_copy(&matrix_mdev->matrix, &m_new);
+	ap_matrix_copy(&matrix_mdev->matrix, m_new);
 
 	/* Ensure new state is valid, else undo new state */
-	rc = vfio_ap_mdev_validate_masks(matrix_mdev);
-	if (rc) {
-		ap_matrix_copy(&matrix_mdev->matrix, &m_old);
-		goto out;
-	}
-	rc = ap_matrix_overflow_check(matrix_mdev);
+	rc = validate_new_state(matrix_mdev);
 	if (rc) {
 		ap_matrix_copy(&matrix_mdev->matrix, &m_old);
-		goto out;
+		ap_matrix_copy(&matrix_mdev->shadow_apcb, &m_old_shadow);
+		return rc;
 	}
-	rc = count;
 
 	/* Need old bitmaps in matrix_mdev for unplug/unlink */
 	ap_matrix_copy(&matrix_mdev->matrix, &m_old);
@@ -1786,14 +1785,10 @@ static ssize_t ap_config_store(struct device *dev, struct device_attribute *attr
 	vfio_ap_mdev_hot_unplug_domains(matrix_mdev, m_removed.aqm);
 
 	/* Need new bitmaps in matrix_mdev for linking new adapters/domains */
-	ap_matrix_copy(&matrix_mdev->matrix, &m_new);
-
-	/* Link newly added adapters */
-	for_each_set_bit_inv(newbit, m_added.apm, AP_DEVICES)
-		vfio_ap_mdev_link_adapter(matrix_mdev, newbit);
+	ap_matrix_copy(&matrix_mdev->matrix, m_new);
 
-	for_each_set_bit_inv(newbit, m_added.aqm, AP_DOMAINS)
-		vfio_ap_mdev_link_domain(matrix_mdev, newbit);
+	/* Link queues associated with the newly added adapters and domains */
+	link_new_queues(matrix_mdev, &m_added);
 
 	/* filter resources not bound to vfio-ap */
 	do_update = vfio_ap_mdev_filter_matrix(matrix_mdev, apm_filtered);
@@ -1804,7 +1799,39 @@ static ssize_t ap_config_store(struct device *dev, struct device_attribute *attr
 		vfio_ap_mdev_update_guest_apcb(matrix_mdev);
 		reset_queues_for_apids(matrix_mdev, apm_filtered);
 	}
-out:
+
+	return 0;
+}
+
+static ssize_t ap_config_store(struct device *dev, struct device_attribute *attr,
+			       const char *buf, size_t count)
+{
+	struct ap_matrix_mdev *matrix_mdev = dev_get_drvdata(dev);
+	struct ap_matrix m_new;
+	char *newbuf, *rest;
+	ssize_t rc;
+
+	newbuf = kstrndup(buf, AP_CONFIG_STRLEN, GFP_KERNEL);
+	if (!newbuf)
+		return -ENOMEM;
+	rest = newbuf;
+
+	mutex_lock(&ap_attr_mutex);
+	get_update_locks_for_mdev(matrix_mdev);
+
+	if (parse_bitmap(&rest, m_new.apm, AP_DEVICES) ||
+	    parse_bitmap(&rest, m_new.aqm, AP_DOMAINS) ||
+	    parse_bitmap(&rest, m_new.adm, AP_DOMAINS)) {
+		kfree(newbuf);
+		release_update_locks_for_mdev(matrix_mdev);
+		mutex_unlock(&ap_attr_mutex);
+		return -EINVAL;
+	}
+
+	rc = vfio_ap_set_new_guest_config(matrix_mdev, &m_new);
+	if (!rc)
+		rc = count;
+
 	release_update_locks_for_mdev(matrix_mdev);
 	mutex_unlock(&ap_attr_mutex);
 	kfree(newbuf);
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index 1fbdfcce5a11..150dfce8a674 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -157,6 +157,62 @@ struct vfio_ap_queue {
 	struct work_struct reset_work;
 };
 
+/**
+ * get_update_locks_for_mdev: Acquire the locks required to dynamically update a
+ *			      KVM guest's APCB in the proper order.
+ *
+ * @matrix_mdev: a pointer to a struct ap_matrix_mdev object containing the AP
+ *		 configuration data to use to update a KVM guest's APCB.
+ *
+ * The proper locking order is:
+ * 1. matrix_dev->guests_lock: required to use the KVM pointer to update a KVM
+ *			       guest's APCB.
+ * 2. matrix_mdev->kvm->lock:  required to update a guest's APCB
+ * 3. matrix_dev->mdevs_lock:  required to access data stored in a matrix_mdev
+ *
+ * Note: If @matrix_mdev is NULL or is not attached to a KVM guest, the KVM
+ *	 lock will not be taken.
+ */
+static inline void get_update_locks_for_mdev(struct ap_matrix_mdev *matrix_mdev)
+{
+	mutex_lock(&matrix_dev->guests_lock);
+	if (matrix_mdev && matrix_mdev->kvm)
+		mutex_lock(&matrix_mdev->kvm->lock);
+	mutex_lock(&matrix_dev->mdevs_lock);
+}
+
+/**
+ * release_update_locks_for_mdev: Release the locks used to dynamically update a
+ *				  KVM guest's APCB in the proper order.
+ *
+ * @matrix_mdev: a pointer to a struct ap_matrix_mdev object containing the AP
+ *		 configuration data to use to update a KVM guest's APCB.
+ *
+ * The proper unlocking order is:
+ * 1. matrix_dev->mdevs_lock
+ * 2. matrix_mdev->kvm->lock
+ * 3. matrix_dev->guests_lock
+ *
+ * Note: If @matrix_mdev is NULL or is not attached to a KVM guest, the KVM
+ *	 lock will not be released.
+ */
+static inline void release_update_locks_for_mdev(struct ap_matrix_mdev *matrix_mdev)
+{
+	mutex_unlock(&matrix_dev->mdevs_lock);
+	if (matrix_mdev && matrix_mdev->kvm)
+		mutex_unlock(&matrix_mdev->kvm->lock);
+	mutex_unlock(&matrix_dev->guests_lock);
+}
+
+static inline void
+assert_has_update_locks_for_mdev(struct ap_matrix_mdev *matrix_mdev)
+{
+	lockdep_assert_held(&matrix_dev->guests_lock);
+	if (matrix_mdev && matrix_mdev->kvm)
+		lockdep_assert_held(&matrix_mdev->kvm->lock);
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+}
+
 int vfio_ap_mdev_get_num_queues(struct ap_matrix *ap_matrix);
 
 int vfio_ap_mdev_register(void);
@@ -172,9 +228,14 @@ void vfio_ap_on_cfg_changed(struct ap_config_info *new_config_info,
 void vfio_ap_on_scan_complete(struct ap_config_info *new_config_info,
 			      struct ap_config_info *old_config_info);
 
+void vfio_ap_matrix_init(struct ap_config_info *info, struct ap_matrix *matrix);
+
 void vfio_ap_init_migration_capabilities(struct ap_matrix_mdev *matrix_mdev);
 int vfio_ap_init_migration_data(struct ap_matrix_mdev *matrix_mdev);
 void vfio_ap_release_migration_data(struct ap_matrix_mdev *matrix_mdev);
 void vfio_ap_reset_migration_state(struct ap_matrix_mdev *matrix_mdev);
 
+int vfio_ap_set_new_guest_config(struct ap_matrix_mdev *matrix_mdev,
+				 struct ap_matrix *m_new);
+
 #endif /* _VFIO_AP_PRIVATE_H_ */
-- 
2.53.0

[PATCH v6 10/15] s390/vfio-ap: File ops called to resume the vfio device migration

[Anthony Krowiak]

Implements the 'write' callback function that was added to the
'file_operations' structure for the file stream created to restore the
state of the vfio-ap device on the destination system when the migration
state transitioned from STOP to RESUMING

The write callback retrieves the vfio device migration state saved to the
file stream created when the vfio device state was transitioned from
STOP to STOP_COPY. The saved state contains the source guest's AP
configuration information. This data is copied from the userspace buffer
passed to the 'write' callback and stored in the vfio_ap_config structure
used to set the state of the vfio-ap device on the destination host. If the
source guest's AP configuration is compatible with the AP configuration on
the destination host, it will be hot plugged into the destination guest.

In order for the source guest's and destination host's AP configurations
to be considered compatible:

* Each APQN in the source guest's AP configuration must also be in the
  destination host's AP configuration

* Each matching APQN in the destination host's AP configuration must be
  bound to the vfio_ap device driver

* Each matching APQN in the destination host's AP configuration must
  reference a queue device with compatible hardware:

  - The source and destination queues must have the same facilities
    installed:
    ~ APSC facility
    ~ APQKM facility
    ~ AP4KC facility

  - The source and destination queues must have the same mode:
    ~ Coprocessor-mode
    ~ Accelerator-mode
    ~ XCP-mode

  - The source and destination queues must have the same APXA facility
    setting
    ~ If the APXA facility is installed on source queue, it must also
      be installed on the destination queue and vice versa

  - The source and destination queues must have a compatible
    classification setting. If the source queue has full native card
    function, then the destination queue must also have full native
    card function. If the source queue has stateless functions, then
    the destination queue can have stateless functions or full native card
    function because the latter includes the stateless functions.

  - The binding and associated state for both the source and destination
    queues must indicate that the queue is usable for all messages
    (i.e., BS bits equal to 00).

  - The AP type of the destination queue must be the same as or newer than
    the source queue (backward compatibility)

Note: The get_hardware_info_for_queue function that was created in
      a previous patch was modified to take a mediated device name rather
      than an ap_matrix_mdev object because that is what is needed for
      this patch so the function can be executed without holding the
      matrix_dev->mdevs_lock.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_migration.c | 805 +++++++++++++++++++++++-
 1 file changed, 797 insertions(+), 8 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index c7fecad0b676..c12ba82ec527 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -8,6 +8,54 @@
 #include <linux/file.h>
 #include "vfio_ap_private.h"
 
+/*
+ * Masks the fields of the queue information returned from the PQAP(TAPQ)
+ * command. In order to migrate a guest, it's AP configuration must be
+ * compatible with AP configuration assigned to the target guest's mdev.
+ * This mask is used to verify that the queue information for each source and
+ * target queue is compatible.
+ *
+ * The following bits must match for the source device and the corresponding
+ * destination device:
+ * -------------------------------------------------------------------------
+ * S bit 0: APSC  facility installed
+ * M bit 1: APQKM facility installed
+ * C bit 2: AP4KC facility installed
+ * Mode bits 3-5:
+ *     D bit 3: CCA-mode facility
+ *     A bit 4: accelerator-mode facility
+ *     X bit 5: XCP-mode facility
+ * N  bit 6: APXA facility installed
+ * SL bit 7: SLCF facility installed
+ *
+ * Either bit 8 or bit 9 will be set. If bit 8 is set for the source device,
+ * then it must also be set for the corresponding destination device:
+ * -------------------------------------------------------------------------
+ * Classification (functional capabilities) bits 8-16
+ *     bit 8: Native card function
+ *     bit 9: Only stateless functions
+ *
+ * The BS bits must be set to 0 for both the source and corresponding
+ * destination device:
+ * -------------------------------------------------------------------------
+ * BS bits 16-17:
+ *
+ * The AP type of the source device must be less than or equal to that of
+ * the corresponding destination device:
+ * -------------------------------------------------------------------------
+ * AP Type bits 32-40:
+ */
+#define QINFO_DATA_MASK		0xffffc000ff000000
+
+/*
+ * Masks the bit that indicates whether full native card function is available
+ * from the 8 bits specifying the functional capabilities of a queue
+ */
+#define CLASSIFICATION_NATIVE_FCN_MASK		0x80
+
+/* The maximum number of queues that can be installed in an s390 system */
+#define MAX_AP_QUEUES				(AP_DEVICES * AP_DOMAINS)
+
 /**
  * struct vfio_ap_migration_file
  *
@@ -85,7 +133,7 @@ vfio_ap_release_stop_copy_file(struct vfio_ap_migration_data *mig_data)
 static void
 vfio_ap_release_resuming_file(struct vfio_ap_migration_data *mig_data)
 {
-	kfree(mig_data->resuming_mig_file.ap_config);
+	kvfree(mig_data->resuming_mig_file.ap_config);
 	mig_data->resuming_mig_file.ap_config = NULL;
 	mig_data->resuming_mig_file.config_sz = 0;
 	mig_data->resuming_mig_file.filp = NULL;
@@ -213,8 +261,6 @@ static int get_hardware_info_for_queue(const char *mdev_name,
 		       status.response_code);
 		return -EIO;
 	}
-
-	return -EINVAL;
 }
 
 static int vfio_ap_store_queue_info(const char *mdev_name,
@@ -244,15 +290,16 @@ static int vfio_ap_store_queue_info(const char *mdev_name,
 
 static int vfio_ap_get_config(struct ap_matrix_mdev *matrix_mdev)
 {
-	unsigned long *apm, *aqm, apid, apqi, num_queues;
+	unsigned long *apm, *aqm, apid, apqi;
 	struct vfio_ap_config *ap_configuration;
 	const char *mdev_name;
 	size_t ap_config_size;
+	int num_queues;
 	int ret;
 
 	lockdep_assert_held(&matrix_dev->mdevs_lock);
 
-	ap_config_size = vfio_ap_config_size(matrix_mdev, (int *)&num_queues);
+	ap_config_size = vfio_ap_config_size(matrix_mdev, &num_queues);
 
 	ap_configuration = kzalloc(ap_config_size, GFP_KERNEL_ACCOUNT);
 	if (!ap_configuration)
@@ -411,11 +458,753 @@ static struct file *vfio_ap_open_file_stream(struct ap_matrix_mdev *matrix_mdev,
 	return filp;
 }
 
+static int validate_resuming_write_parms(struct file *filp,
+					 size_t len, loff_t *pos)
+{
+	struct ap_matrix_mdev *matrix_mdev;
+	loff_t total_len;
+
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	if (!len || *pos < 0)
+		return -EINVAL;
+
+	if (check_add_overflow((loff_t)len, *pos, &total_len))
+		return -ERANGE;
+
+	matrix_mdev = filp->private_data;
+	if (!matrix_mdev || !matrix_mdev->mig_data)
+		return -ENODEV;
+
+	if (filp != matrix_mdev->mig_data->resuming_mig_file.filp)
+		return -ENXIO;
+
+	/*
+	 * If the ap_config has not yet been allocated and the file position
+	 * indicates this is not the first write, or the ap_config has been allocated
+	 * but the file position indicates this is the first write, then this is an
+	 * error condition.
+	 */
+	if ((!matrix_mdev->mig_data->resuming_mig_file.ap_config && *pos != 0) ||
+	    (matrix_mdev->mig_data->resuming_mig_file.ap_config && *pos == 0))
+		return -EFAULT;
+
+	/*
+	 * The first write must cover at least num_queues (the first field of
+	 * struct vfio_ap_config) so that allocate_ap_config() can derive the
+	 * correct allocation size.  A shorter first write would cause
+	 * cfg_sz to be set to len, the completion check
+	 * (write_pos + len == cfg_sz) would fire immediately, and
+	 * do_post_copy_validation() would read qinfo[] from a buffer that
+	 * is too small to contain it.
+	 */
+	if (*pos == 0 && len < offsetofend(struct vfio_ap_config, num_queues))
+		return -EINVAL;
+
+	return 0;
+}
+
+static ssize_t calculate_ap_config_size(unsigned int num_queues)
+{
+	size_t qinfo_size;
+
+	if (num_queues > MAX_AP_QUEUES)
+		return -EINVAL;
+
+	qinfo_size = num_queues * sizeof(struct vfio_ap_queue_info);
+	return qinfo_size + sizeof(struct vfio_ap_config);
+}
+
+/**
+ * allocate_ap_config:
+ *
+ * Allocate storage for the source guest's AP configuration data sent from
+ * userspace.
+ *
+ * @ap_config:	The location in which to store the pointer to the storage
+ *		allocated for the AP configuration data.
+ * @buf:	The userspace buffer containing some or all of the source
+ *		guest's AP configuration data
+ * @len:	The number of bytes of data to copy from @buf
+ *
+ * Returns:	The number of bytes of storage allocated for the config data or
+ *		an error:
+ *
+ *		-EINVAL: len is 0, or num_queues exceeds the maximum (only checked
+ *			 if @len covers the full vfio_ap_config header)
+ *		-EIO: failed to copy data from @buf
+ *		-ENOMEM: the allocation of storage failed
+ */
+static ssize_t allocate_ap_config(struct vfio_ap_config **ap_config,
+				  const char __user *buf, size_t len)
+{
+	struct vfio_ap_config tmp_ap_config;
+	ssize_t config_size;
+
+	/*
+	 * validate_resuming_write_parms() guarantees the first write covers at
+	 * least num_queues, so we can always derive the final allocation size
+	 * here.
+	 */
+	if (copy_from_user(&tmp_ap_config, buf, min(len, sizeof(tmp_ap_config))))
+		return -EIO;
+
+	config_size = calculate_ap_config_size(tmp_ap_config.num_queues);
+	if (config_size < 0)
+		return config_size;
+
+	/*
+	 * Use kvzalloc so that large configurations can fall back to vmalloc
+	 * rather than failing a high-order contiguous physical allocation.
+	 */
+	*ap_config = kvzalloc(config_size, GFP_KERNEL_ACCOUNT);
+	if (!*ap_config)
+		return -ENOMEM;
+
+	return config_size;
+}
+
+/**
+ * qdev_is_bound_to_vfio_ap:
+ *
+ * Query to determine whether a queue with the specified APQN is available on
+ * the host system and bound to the vfio_ap device driver.
+ *
+ * @apqn: The APQN of the queue device being queried
+ *
+ * Returns: True if there is a queue device with the specified @apqn installed
+ *	    in the system and is bound to the vfio_ap device driver; otherwise,
+ *	    returns false.
+ */
+static bool qdev_is_bound_to_vfio_ap(unsigned int apqn)
+{
+	struct ap_queue *queue;
+	bool is_bound = true;
+
+	queue = ap_get_qdev(apqn);
+	if (!queue)
+		return false;
+
+	if (queue->ap_dev.device.driver != &matrix_dev->vfio_ap_drv->driver)
+		is_bound = false;
+
+	put_device(&queue->ap_dev.device);
+
+	return is_bound;
+}
+
+/**
+ * queues_available:
+ *
+ * Query whether each queue from the source guest's AP configuration is
+ * available and bound to the vfio_ap device driver; if not, log an error
+ * message.
+ *
+ * @mdev_name:	   The mdev name to use in error messages
+ * @source_config: The object specifying the source guest's AP configuration
+ *
+ * Returns: true if each queue identified in @source_config is available and
+ *	    bound to the vfio_ap device driver; otherwise, returns false.
+ */
+static bool queues_available(const char *mdev_name,
+			     struct vfio_ap_config *source_config)
+{
+	unsigned long apqn;
+	bool ret = true;
+
+	for (int i = 0; i < source_config->num_queues; i++) {
+		apqn = source_config->qinfo[i].apqn;
+
+		/*
+		 * Find the queue device bound to the vfio_ap device driver. If it is
+		 * not found, log an error and continue so users see all problems
+		 * at once, not one-at-a-time through retries of the migration.
+		 */
+		if (!qdev_is_bound_to_vfio_ap(apqn)) {
+			pr_err("vfio_ap_mdev %s: Queue %02lx.%04lx not available to vfio_ap driver on target host\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+			ret = false;
+		}
+	}
+
+	return ret;
+}
+
+/**
+ * control_domains_available
+ *
+ * Query whether each control domain specified in the source guest's AP
+ * configuration is installed in the host system.
+ *
+ * @mdev_name:		The name of the mdev to use when logging messages
+ * @source_config:	The object specifying the source guest's AP config
+ *
+ * Returns:	True if each control domain is installed; otherwise, logs an
+ *		error message for each unavailable control domain and returns
+ *		false.
+ */
+static bool control_domains_available(const char *mdev_name,
+				      struct vfio_ap_config *source_config)
+{
+	unsigned long domain_num;
+	bool available = true;
+
+	for_each_set_bit_inv(domain_num, (unsigned long *)source_config->adm,
+			     AP_DOMAINS) {
+		if (!ap_test_config_ctrl_domain(domain_num)) {
+			pr_err("vfio_ap_mdev: %s: Control domain %04lx not available on the destination host",
+			       mdev_name, domain_num);
+			available = false;
+		}
+	}
+
+	return available;
+}
+
+static void report_facilities_compatibility(const char *mdev_name,
+					    unsigned long apqn,
+					    struct ap_tapq_hwinfo *src_hwinfo,
+					    struct ap_tapq_hwinfo *target_hwinfo)
+{
+	if (src_hwinfo->apsc != target_hwinfo->apsc) {
+		if (src_hwinfo->apsc) {
+			pr_err("vfio_ap_mdev %s: APSC facility installed in source queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err("vfio_ap_mdev %s: APSC facility not installed in target queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		} else {
+			pr_err("vfio_ap_mdev %s: APSC facility not installed in source queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err("vfio_ap_mdev %s APSC facility installed in target queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		}
+	}
+
+	if (src_hwinfo->mex4k != target_hwinfo->mex4k) {
+		if (src_hwinfo->mex4k) {
+			pr_err("vfio_ap_mdev %s: mex4k facility installed in source queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err("vfio_ap_mdev %s: mex4k facility not installed in target queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		} else {
+			pr_err("vfio_ap_mdev %s: mex4k facility not installed in source queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err("vfio_ap_mdev %s: mex4k facility installed in target queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		}
+	}
+
+	if (src_hwinfo->crt4k != target_hwinfo->crt4k) {
+		if (src_hwinfo->crt4k) {
+			pr_err("vfio_ap_mdev %s: crt4k facility installed in source queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err("vfio_ap_mdev %s: crt4k facility not installed in target queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		} else {
+			pr_err("vfio_ap_mdev %s: crt4k facility not installed in source queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err("vfio_ap_mdev %s: crt4k facility installed in target queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		}
+	}
+}
+
+static void report_mode_compatibility(const char *mdev_name,
+				      unsigned long apqn,
+				      struct ap_tapq_hwinfo *src_hwinfo,
+				      struct ap_tapq_hwinfo *target_hwinfo)
+{
+	if (src_hwinfo->cca != target_hwinfo->cca) {
+		if (src_hwinfo->cca) {
+			pr_err("vfio_ap_mdev %s: Coprocessor-mode facility installed in source queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err("vfio_ap_mdev %s: Coprocessor-mode  facility not installed target queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		} else {
+			pr_err("vfio_ap_mdev %s: Coprocessor-mode facility not installed in source queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err("vfio_ap_mdev %s: Coprocessor-mode  facility installed target queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		}
+	}
+
+	if (src_hwinfo->accel != target_hwinfo->accel) {
+		if (src_hwinfo->accel) {
+			pr_err("vfio_ap_mdev %s: Accelerator-mode facility installed source queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err("vfio_ap_mdev %s: Accelerator-mode facility not installed target queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		} else {
+			pr_err("vfio_ap_mdev %s: Accelerator-mode facility not installed source queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err("vfio_ap_mdev %s: Accelerator-mode facility installed target queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		}
+	}
+
+	if (src_hwinfo->ep11 != target_hwinfo->ep11) {
+		if (src_hwinfo->ep11) {
+			pr_err("vfio_ap_mdev %s: XCP-mode facility installed source queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err("vfio_ap_mdev %s: XCP-mode facility not installed target queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		} else {
+			pr_err("vfio_ap_mdev %s: XCP-mode facility not installed source queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err("vfio_ap_mdev %s: XCP-mode facility installed target queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		}
+	}
+}
+
+static void report_apxa_compatibility(const char *mdev_name,
+				      unsigned long apqn,
+				      struct ap_tapq_hwinfo *src_hwinfo,
+				      struct ap_tapq_hwinfo *target_hwinfo)
+{
+	if (src_hwinfo->apxa != target_hwinfo->apxa) {
+		if (src_hwinfo->apxa) {
+			pr_err("vfio_ap_mdev %s: AP-extended-addressing (APXA) facility installed in source queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err("vfio_ap_mdev %s: AP-extended-addressing (APXA) facility not installed in target queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		} else {
+			pr_err("vfio_ap_mdev %s: AP-extended-addressing (APXA) facility not installed in source queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err("vfio_ap_mdev %s: AP-extended-addressing (APXA) facility installed in target queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		}
+	}
+}
+
+static void report_slcf_compatibility(const char *mdev_name,
+				      unsigned long apqn,
+				      struct ap_tapq_hwinfo *src_hwinfo,
+				      struct ap_tapq_hwinfo *target_hwinfo)
+{
+	if (src_hwinfo->slcf != target_hwinfo->slcf) {
+		if (src_hwinfo->slcf) {
+			pr_err("vfio_ap_mdev %s: Stateless-command-filtering (SLCF) available in source queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err("vfio_ap_mdev %s: Stateless-command-filtering (SLCF) not available in target queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		} else {
+			pr_err("vfio_ap_mdev %s: Stateless-command-filtering (SLCF) not available in source queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err("vfio_ap_mdev %s: Stateless-command-filtering (SLCF) available in target queue %02lx.%04lx\n",
+			       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		}
+	}
+}
+
+static void report_bs_compatibility(const char *mdev_name,
+				    unsigned long apqn,
+				    struct ap_tapq_hwinfo *src_hwinfo,
+				    struct ap_tapq_hwinfo *target_hwinfo)
+{
+	/*
+	 * The BS field on both the source and destination must be 0, so if one
+	 * of them is not, then report an error.
+	 */
+	if (src_hwinfo->bs || target_hwinfo->bs) {
+		pr_err("vfio_ap_mdev %s: Bind/associate state for source (%01x) and target (%01x) queue %02lx.%04lx must be 0\n",
+		       mdev_name, src_hwinfo->bs, target_hwinfo->bs,
+		       AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+	}
+}
+
+static void report_aptype_compatibility(const char *mdev_name,
+					unsigned long apqn,
+					struct ap_tapq_hwinfo *src_hwinfo,
+					struct ap_tapq_hwinfo *target_hwinfo)
+{
+	if (src_hwinfo->at > target_hwinfo->at) {
+		pr_err("vfio_ap_mdev %s: AP type of source (%02x) not compatible with target (%02x)\n",
+		       mdev_name, src_hwinfo->at, target_hwinfo->at);
+	}
+}
+
+static bool classes_compatible(struct ap_tapq_hwinfo *src_hwinfo,
+			       struct ap_tapq_hwinfo *target_hwinfo)
+{
+	unsigned long src_native, target_native;
+
+	src_native = src_hwinfo->class & CLASSIFICATION_NATIVE_FCN_MASK;
+	target_native = target_hwinfo->class & CLASSIFICATION_NATIVE_FCN_MASK;
+
+	/*
+	 * If the source queue has full native card function and the
+	 * target queue has only stateless functions available, then
+	 * there may be instructions that will not execute on the
+	 * target queue. This shall be reported as an error.
+	 *
+	 * If the source queue has only stateless card functions and the
+	 * target queue has full native card function available, then
+	 * we are okay because the target queue can run all stateless card
+	 * functions.
+	 */
+	return (src_native != target_native) ? !src_native : true;
+}
+
+static void report_class_compatibility(const char *mdev_name,
+				       unsigned long apqn,
+				       struct ap_tapq_hwinfo *src_hwinfo,
+				       struct ap_tapq_hwinfo *target_hwinfo)
+{
+	if (!classes_compatible(src_hwinfo, target_hwinfo)) {
+		pr_err("vfio_ap_mdev %s: Full native card function available on source queue %02lx.%04lx\n",
+		       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+		pr_err("vfio_ap_mdev %s: Only stateless functions available on target queue %02lx.%04lx\n",
+		       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+	}
+}
+
+/*
+ * Log a device error reporting that migration failed due to queue
+ * incompatibilities followed by a device error for each incompatible feature.
+ */
+static void report_qinfo_incompatibilities(const char *mdev_name,
+					   unsigned long apqn,
+					   struct ap_tapq_hwinfo *src_hwinfo,
+					   struct ap_tapq_hwinfo *target_hwinfo)
+{
+	pr_err("vfio_ap_mdev %s: Migration failed: Source and target queue (%02lx.%04lx) not compatible\n",
+	       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+	report_facilities_compatibility(mdev_name, apqn, src_hwinfo, target_hwinfo);
+	report_mode_compatibility(mdev_name, apqn, src_hwinfo, target_hwinfo);
+	report_apxa_compatibility(mdev_name, apqn, src_hwinfo, target_hwinfo);
+	report_slcf_compatibility(mdev_name, apqn, src_hwinfo, target_hwinfo);
+	report_aptype_compatibility(mdev_name, apqn, src_hwinfo, target_hwinfo);
+	report_bs_compatibility(mdev_name, apqn, src_hwinfo, target_hwinfo);
+	report_class_compatibility(mdev_name, apqn, src_hwinfo, target_hwinfo);
+}
+
+/**
+ * queue_hardware_info_is_compatible:
+ *
+ * Verify whether the hardware information for a source queue is compatible with
+ * the hardware info for the corresponding queue on this system.
+ *
+ * In order to be compatible, the hardware information for each queue must
+ * meet the following requirements:
+ *
+ * 1. The hardware facilities bits much match
+ * 2. The AP type of the source queue must be the same as or older than that
+ *    of the target queue (target is backwards compatible)
+ * 3. The classification bits must indicate:
+ *    - Both queues have full native card function or both have stateless
+ *      functions available
+ *    - If the classification bits don't match, then the only acceptable
+ *      configuration is stateless functions for the source queue and
+ *      full native function for the target queue
+ * 4. The BS bits for both queues must be 0 (Queue usable for all messages
+ *    supported by the adapter)
+ *
+ * @mdev_name:	The mdev name to use in error messages
+ * @apqn:	The APQN for the queues
+ * @src_hwinfo: The hardware info for the source queue
+ * @target_hwinfo: The hardware info for the corresponding queue on this system
+ *
+ * Returns: true if the hardware info for the two queues is compatible;
+ *          otherwise, returns false.
+ */
+static bool queue_hardware_info_is_compatible(const char *mdev_name,
+					      unsigned long apqn,
+					      struct ap_tapq_hwinfo *src_hwinfo,
+					      struct ap_tapq_hwinfo *target_hwinfo)
+{
+	unsigned long src_bits, target_bits;
+
+	src_bits = src_hwinfo->value & QINFO_DATA_MASK;
+	target_bits = target_hwinfo->value & QINFO_DATA_MASK;
+
+	/* If all bits match the queues are compatible */
+	if (src_bits == target_bits &&
+	    (src_hwinfo->bs == 0 && target_hwinfo->bs == 0))
+		return true;
+
+	if (src_hwinfo->apsc  == target_hwinfo->apsc     &&
+	    src_hwinfo->mex4k == target_hwinfo->mex4k    &&
+	    src_hwinfo->crt4k == target_hwinfo->crt4k    &&
+	    src_hwinfo->cca   == target_hwinfo->cca      &&
+	    src_hwinfo->accel == target_hwinfo->accel    &&
+	    src_hwinfo->ep11  == target_hwinfo->ep11     &&
+	    src_hwinfo->slcf  == target_hwinfo->slcf     &&
+	    src_hwinfo->apxa  == target_hwinfo->apxa     &&
+	    src_hwinfo->at    <= target_hwinfo->at       &&
+	    classes_compatible(src_hwinfo, target_hwinfo) &&
+	    (src_hwinfo->bs == 0 && target_hwinfo->bs == 0))
+		return true;
+
+	report_qinfo_incompatibilities(mdev_name, apqn, src_hwinfo, target_hwinfo);
+
+	return false;
+}
+
+/**
+ * verify_ap_configs_are_compatible:
+ *
+ * Verifies that the queues in the source guest's AP configuration are
+ * compatible with the corresponding queues on this system.
+ *
+ * @mdev_name:	   The mdev name to use in error messages
+ * @source_config: The object specifying the source guest's AP configuration
+ *
+ * Returns: an error indicating either a failure to retrieve a queue's
+ *			hardware information or one or more source queues are not
+ *			compatible with the corresponding queue on this system; otherwise,
+ *			returns zero to indicate compatibility.
+ */
+static int verify_ap_configs_are_compatible(const char *mdev_name,
+					    struct vfio_ap_config *source_config)
+{
+	struct ap_tapq_hwinfo src_hwinfo, dest_hwinfo;
+	unsigned long apqn;
+	int ret = 0, rc;
+
+	for (int i = 0; i < source_config->num_queues; i++) {
+		apqn = source_config->qinfo[i].apqn;
+
+		/*
+		 * If we can't get the hardware info for a particular queue, then let's
+		 * capture the function return code and continue so we can log all
+		 * errors to aid in debugging of migration.
+		 */
+		rc = get_hardware_info_for_queue(mdev_name, &dest_hwinfo, apqn);
+		if (rc) {
+			ret = rc;
+			continue;
+		}
+
+		src_hwinfo.value =  source_config->qinfo[i].data;
+
+		if (!queue_hardware_info_is_compatible(mdev_name, apqn,
+						       &src_hwinfo,
+						       &dest_hwinfo))
+			ret = -EINVAL;
+	}
+
+	return ret;
+}
+
+static int do_post_copy_validation(const char *mdev_name,
+				   struct vfio_ap_config *source_config)
+{
+	if (!queues_available(mdev_name, source_config))
+		return -ENODEV;
+
+	if (!control_domains_available(mdev_name, source_config))
+		return -ENODEV;
+
+	return verify_ap_configs_are_compatible(mdev_name, source_config);
+}
+
+/**
+ * setup_ap_matrix_from_ap_config:
+ *
+ * Set the bits corresponding to the adapters, domains and control domains
+ * from the source guest's AP configuration into an ap_matrix object to be
+ * used to update the destination guest to run on this host.
+ *
+ * @ap_config:		The source guest's AP configuration
+ * @guest_matrix:	The object to be used to update the destination guest's
+ *			AP configuration
+ */
+static void setup_ap_matrix_from_ap_config(struct vfio_ap_config *ap_config,
+					   struct ap_matrix *guest_matrix)
+{
+	struct ap_config_info host_config_info = { 0 };
+	unsigned long apid, apqi, *guest_adm;
+	struct vfio_ap_queue_info qinfo;
+
+	ap_qci(&host_config_info);
+	/*
+	 * Zero the bitmaps before calling vfio_ap_matrix_init(), which only
+	 * sets the apm_max/aqm_max/adm_max scalar fields and leaves the bitmap
+	 * arrays untouched.  Without this, stack garbage in guest_matrix->apm,
+	 * ->aqm, and ->adm would grant the destination guest access to
+	 * arbitrary unassigned queues and control domains.
+	 */
+	memset(guest_matrix->apm, 0, sizeof(guest_matrix->apm));
+	memset(guest_matrix->aqm, 0, sizeof(guest_matrix->aqm));
+	memset(guest_matrix->adm, 0, sizeof(guest_matrix->adm));
+	vfio_ap_matrix_init(&host_config_info, guest_matrix);
+
+	for (int i = 0; i < ap_config->num_queues; i++) {
+		qinfo = ap_config->qinfo[i];
+		apid = AP_QID_CARD(qinfo.apqn);
+		apqi = AP_QID_QUEUE(qinfo.apqn);
+
+		if (!test_bit_inv(apid, guest_matrix->apm))
+			set_bit_inv(apid, guest_matrix->apm);
+		if (!test_bit_inv(apqi, guest_matrix->aqm))
+			set_bit_inv(apqi, guest_matrix->aqm);
+	}
+
+	guest_adm = (unsigned long *)ap_config->adm;
+	for_each_set_bit_inv(apqi, guest_adm, AP_DOMAINS) {
+		if (!test_bit_inv(apqi, guest_matrix->adm))
+			set_bit_inv(apqi, guest_matrix->adm);
+	}
+}
+
 static ssize_t vfio_ap_resuming_write(struct file *filp, const char __user *buf,
 				      size_t len, loff_t *pos)
 {
-	/* TODO */
-	return -EOPNOTSUPP;
+	struct ap_matrix_mdev *matrix_mdev;
+	struct vfio_ap_config *ap_config;
+	struct ap_matrix guest_matrix;
+	bool new_allocation = false;
+	loff_t write_pos;
+	ssize_t ret = 0, cfg_sz;
+	const char *mdev_name;
+
+	/*
+	 * When userspace calls write() with an explicit offset (pwrite), pos is
+	 * non-NULL and the function rejects it with -ESPIPE (illegal seek). For
+	 * normal write() calls, pos is NULL, so we'll use the file's internal
+	 * position filp->f_pos
+	 */
+	if (pos)
+		return -ESPIPE;
+
+	mutex_lock(&matrix_dev->mdevs_lock);
+	pos = &filp->f_pos;
+
+	ret = validate_resuming_write_parms(filp, len, pos);
+	if (ret) {
+		mutex_unlock(&matrix_dev->mdevs_lock);
+		return ret;
+	}
+
+	matrix_mdev = filp->private_data;
+	mdev_name = dev_name(matrix_mdev->vdev.dev);
+
+	/*
+	 * If this is the first write operation, allocate storage for the AP
+	 * configuration sized to fit the full payload (validate_resuming_write_parms
+	 * guarantees num_queues is present in buf).  For subsequent writes the
+	 * buffer is already correctly sized; just reuse it.
+	 */
+	if (*pos == 0) {
+		ret = allocate_ap_config(&ap_config, buf, len);
+		if (ret < 0) {
+			mutex_unlock(&matrix_dev->mdevs_lock);
+			return ret;
+		}
+
+		cfg_sz = ret;
+		new_allocation = true;
+	} else {
+		ap_config = matrix_mdev->mig_data->resuming_mig_file.ap_config;
+		cfg_sz = matrix_mdev->mig_data->resuming_mig_file.config_sz;
+	}
+
+	if (*pos + len > cfg_sz) {
+		if (new_allocation)
+			kvfree(ap_config);
+		mutex_unlock(&matrix_dev->mdevs_lock);
+		return -EIO;
+	}
+
+	/*
+	 * Snapshot and advance *pos under the lock before dropping it for
+	 * copy_from_user().  This prevents concurrent write()s on the same
+	 * stream file from computing the same destination offset and clobbering
+	 * each other's data or racing to reassign mig_data->resuming_mig_file.
+	 */
+	write_pos = *pos;
+	*pos += len;
+
+	mutex_unlock(&matrix_dev->mdevs_lock);
+
+	if (copy_from_user((char *)ap_config + write_pos, buf, len)) {
+		if (new_allocation)
+			kvfree(ap_config);
+		return -EIO;
+	}
+
+	/* Check if we've completed writing the entire configuration */
+	if (write_pos + len == cfg_sz) {
+		/*
+		 * do_post_copy_validation() calls ap_tapq() which is a slow
+		 * hardware instruction.  Run it before acquiring the update
+		 * locks to avoid holding guests_lock, kvm->lock, and
+		 * mdevs_lock across the hardware calls.
+		 */
+		ret = do_post_copy_validation(mdev_name, ap_config);
+		if (ret < 0) {
+			if (new_allocation)
+				kvfree(ap_config);
+			return ret;
+		}
+
+		setup_ap_matrix_from_ap_config(ap_config, &guest_matrix);
+
+		mutex_lock(&ap_attr_mutex);
+		get_update_locks_for_mdev(matrix_mdev);
+
+		/*
+		 * Verify the device wasn't closed while mdevs_lock was dropped
+		 * for the copy_from_user and do_post_copy_validation above.
+		 * get_update_locks_for_mdev() reacquires mdevs_lock.
+		 */
+		if (!matrix_mdev->mig_data) {
+			release_update_locks_for_mdev(matrix_mdev);
+			mutex_unlock(&ap_attr_mutex);
+			if (new_allocation)
+				kvfree(ap_config);
+			return -ENODEV;
+		}
+
+		ret = vfio_ap_set_new_guest_config(matrix_mdev, &guest_matrix);
+
+		release_update_locks_for_mdev(matrix_mdev);
+		mutex_unlock(&ap_attr_mutex);
+
+		if (ret) {
+			if (new_allocation)
+				kvfree(ap_config);
+			return ret;
+		}
+	}
+
+	mutex_lock(&matrix_dev->mdevs_lock);
+	/*
+	 * Re-read mig_data under the lock; the device could have been closed
+	 * concurrently while the lock was dropped for copy_from_user().
+	 */
+	if (!matrix_mdev->mig_data) {
+		mutex_unlock(&matrix_dev->mdevs_lock);
+		if (new_allocation)
+			kvfree(ap_config);
+		return -ENODEV;
+	}
+	if (new_allocation)
+		kvfree(matrix_mdev->mig_data->resuming_mig_file.ap_config);
+	matrix_mdev->mig_data->resuming_mig_file.ap_config = ap_config;
+	matrix_mdev->mig_data->resuming_mig_file.config_sz = cfg_sz;
+	mutex_unlock(&matrix_dev->mdevs_lock);
+
+	return len;
 }
 
 static const struct file_operations vfio_ap_resume_fops = {
@@ -669,7 +1458,7 @@ static void vfio_ap_release_mig_files(struct ap_matrix_mdev *matrix_mdev)
 		mig_data->resuming_mig_file.filp = NULL;
 	}
 
-	kfree(mig_data->resuming_mig_file.ap_config);
+	kvfree(mig_data->resuming_mig_file.ap_config);
 	mig_data->resuming_mig_file.ap_config = NULL;
 	mig_data->resuming_mig_file.config_sz = 0;
 }
-- 
2.53.0

[PATCH v6 11/15] s390/vfio-ap: Transition device migration state to STOP

[Anthony Krowiak]

Typically at this point, interrupt processing for the device, DMA and other
changes to the device's external state must be prohibited. For VFIO AP,
there is no physical DMA device virtualized by the vfio-ap device . It
merely manages the guest's AP configuration that identifies the devices
passed through to the guest, but does not have access to any of them. Those
AP devices are passed through and controlled exclusively by the SIE program
used to start the guest. There  only thing to do at this point is return
NULL to the caller since the file streams and associated data will get
cleaned up as a result of the VFIO migration framework releasing the files.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_migration.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index c12ba82ec527..fc4cb893f0f0 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -1267,12 +1267,17 @@ vfio_ap_transition_to_state(struct ap_matrix_mdev *matrix_mdev,
 		return filp;
 	}
 
+	/*
+	 * Terminates the data transfer session of the vfio-ap device state
+	 * between the source and target hosts. Since the vfio-ap device does
+	 * not virtualize a DMA device, there is no internal device state to
+	 * incorporate into the vfio-ap device on the target.
+	 */
 	if ((cur_state == VFIO_DEVICE_STATE_RESUMING &&
 	     new_state == VFIO_DEVICE_STATE_STOP) ||
 	    (cur_state == VFIO_DEVICE_STATE_STOP_COPY &&
 	     new_state == VFIO_DEVICE_STATE_STOP)) {
-		/* TODO */
-		return ERR_PTR(-EOPNOTSUPP);
+		return NULL;
 	}
 
 	if ((cur_state == VFIO_DEVICE_STATE_STOP &&
-- 
2.53.0

[PATCH v6 12/15] s390/vfio-ap: Transition device migration state from STOP to RUNNING and vice versa

[Anthony Krowiak]

The transition from STOP to RUNNING and vice versa indicates that
the vfio device is operating normally and migration is not
currently taking place. In this case, just set the new state.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_migration.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index fc4cb893f0f0..1c385908fc39 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -1280,12 +1280,17 @@ vfio_ap_transition_to_state(struct ap_matrix_mdev *matrix_mdev,
 		return NULL;
 	}
 
+	/*
+	 * These states indicate migration has either not been initiated or
+	 * has completed and the vfio-ap device is operating normally. Since the
+	 * vfio-ap device does not virtualize a DMA device, there is no internal
+	 * device state to incorporate into the vfio-ap device on the target.
+	 */
 	if ((cur_state == VFIO_DEVICE_STATE_STOP &&
 	     new_state == VFIO_DEVICE_STATE_RUNNING) ||
 	    (cur_state == VFIO_DEVICE_STATE_RUNNING &&
 	     new_state == VFIO_DEVICE_STATE_STOP)) {
-		/* TODO */
-		return ERR_PTR(-EOPNOTSUPP);
+		return NULL;
 	}
 
 	/* vfio_mig_get_next_state() does not use arcs other than the above */
-- 
2.53.0

[PATCH v6 13/15] s390/vfio-ap: Callback to get the size of data to be migrated during guest migration

[Anthony Krowiak]

Callback to get the estimated data length of the data that will be required
to complete reading of the vfio device's internal state. It's mandatory for
VFIO_DEVICE_FEATURE_MIGRATION migration support.

The function pointer for this callback is specified via the
'migration_get_data_size' field of the 'vfio_migration_ops' structure
which is stored with the VFIO device when the 'vfio_device'
structure representing the mediated device is initialized.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_migration.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index 1c385908fc39..8379cf8bbce8 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -1392,7 +1392,18 @@ static int vfio_ap_get_state(struct vfio_device *vdev,
 static int vfio_ap_get_data_size(struct vfio_device *vdev,
 				 unsigned long *stop_copy_length)
 {
-	return -EOPNOTSUPP;
+	struct ap_matrix_mdev *matrix_mdev;
+	size_t qinfo_sz;
+	int num_queues;
+
+	mutex_lock(&matrix_dev->mdevs_lock);
+	matrix_mdev = container_of(vdev, struct ap_matrix_mdev, vdev);
+	num_queues = vfio_ap_mdev_get_num_queues(&matrix_mdev->shadow_apcb);
+	qinfo_sz = num_queues * sizeof(struct vfio_ap_queue_info);
+	*stop_copy_length = qinfo_sz + sizeof(struct vfio_ap_config);
+	mutex_unlock(&matrix_dev->mdevs_lock);
+
+	return 0;
 }
 
 static const struct vfio_migration_ops vfio_ap_migration_ops = {
-- 
2.53.0

[PATCH v6 14/15] s390/vfio-ap: Add 'migratable' feature to sysfs 'features' attribute

[Anthony Krowiak]

Add the 'migratable' feature to the features provided by the sysfs
/sys/devices/vfio_ap/matrix/feature attribute to indicate that migration
of vfio devices is supported.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_drv.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
index 8e69ed286bb9..4e973736522b 100644
--- a/drivers/s390/crypto/vfio_ap_drv.c
+++ b/drivers/s390/crypto/vfio_ap_drv.c
@@ -26,9 +26,11 @@ MODULE_LICENSE("GPL v2");
 struct ap_matrix_dev *matrix_dev;
 debug_info_t *vfio_ap_dbf_info;
 
+#define FEATURES "guest_matrix hotplug ap_config migratable"
+
 static ssize_t features_show(struct device *dev, struct device_attribute *attr, char *buf)
 {
-	return sysfs_emit(buf, "guest_matrix hotplug ap_config\n");
+	return sysfs_emit(buf, "%s\n", FEATURES);
 }
 static DEVICE_ATTR_RO(features);
 
-- 
2.53.0

[PATCH v6 15/15] s390/vfio-ap: Add live guest migration chapter to vfio-ap.rst

[Anthony Krowiak]

Add a 'Live Guest Migration' chapter to the
Documentation/arch/s390/vfio-ap.rst document to describe the details for
initiating live guest migration for a guest to which AP adapters, domains
and control domains have been passed through.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 Documentation/arch/s390/vfio-ap.rst | 616 +++++++++++++++++++++++-----
 1 file changed, 517 insertions(+), 99 deletions(-)

diff --git a/Documentation/arch/s390/vfio-ap.rst b/Documentation/arch/s390/vfio-ap.rst
index ac0c07f76ddd..02d7cbe5e479 100644
--- a/Documentation/arch/s390/vfio-ap.rst
+++ b/Documentation/arch/s390/vfio-ap.rst
@@ -1012,7 +1012,7 @@ guest_matrix dyn ap_config
 
 the following features are advertised:
 
----------------+---------------------------------------------------------------+
++--------------+---------------------------------------------------------------+
 | Flag         | Description                                                   |
 +==============+===============================================================+
 | guest_matrix | guest_matrix attribute exists. It reports the matrix of       |
@@ -1021,105 +1021,523 @@ the following features are advertised:
 +--------------+---------------------------------------------------------------+
 | dyn          | Indicates hot plug/unplug of AP adapters, domains and control |
 |              | domains for a guest to which the mdev is attached.            |
-+------------+-----------------------------------------------------------------+
++--------------+---------------------------------------------------------------+
 | ap_config    | ap_config interface for one-shot modifications to mdev config |
 +--------------+---------------------------------------------------------------+
+| migratable   | Indicates that live guest migration is supported for guests   |
+|              | to which crypto devices are passed through                    |
++--------------+---------------------------------------------------------------+
 
-Limitations
-===========
-Live guest migration is not supported for guests using AP devices without
-intervention by a system administrator. Before a KVM guest can be migrated,
-the vfio_ap mediated device must be removed. Unfortunately, it can not be
-removed manually (i.e., echo 1 > /sys/devices/vfio_ap/matrix/$UUID/remove) while
-the mdev is in use by a KVM guest. If the guest is being emulated by QEMU,
-its mdev can be hot unplugged from the guest in one of two ways:
-
-1. If the KVM guest was started with libvirt, you can hot unplug the mdev via
-   the following commands:
-
-      virsh detach-device <guestname> <path-to-device-xml>
-
-      For example, to hot unplug mdev 62177883-f1bb-47f0-914d-32a22e3a8804 from
-      the guest named 'my-guest':
-
-         virsh detach-device my-guest ~/config/my-guest-hostdev.xml
-
-            The contents of my-guest-hostdev.xml:
-
-.. code-block:: xml
-
-            <hostdev mode='subsystem' type='mdev' managed='no' model='vfio-ap'>
-              <source>
-                <address uuid='62177883-f1bb-47f0-914d-32a22e3a8804'/>
-              </source>
-            </hostdev>
-
-
-      virsh qemu-monitor-command <guest-name> --hmp "device-del <device-id>"
-
-      For example, to hot unplug the vfio_ap mediated device identified on the
-      qemu command line with 'id=hostdev0' from the guest named 'my-guest':
-
-.. code-block:: sh
-
-         virsh qemu-monitor-command my-guest --hmp "device_del hostdev0"
-
-2. A vfio_ap mediated device can be hot unplugged by attaching the qemu monitor
-   to the guest and using the following qemu monitor command:
-
-      (QEMU) device-del id=<device-id>
-
-      For example, to hot unplug the vfio_ap mediated device that was specified
-      on the qemu command line with 'id=hostdev0' when the guest was started:
-
-         (QEMU) device-del id=hostdev0
-
-After live migration of the KVM guest completes, an AP configuration can be
-restored to the KVM guest by hot plugging a vfio_ap mediated device on the target
-system into the guest in one of two ways:
-
-1. If the KVM guest was started with libvirt, you can hot plug a matrix mediated
-   device into the guest via the following virsh commands:
-
-   virsh attach-device <guestname> <path-to-device-xml>
-
-      For example, to hot plug mdev 62177883-f1bb-47f0-914d-32a22e3a8804 into
-      the guest named 'my-guest':
-
-         virsh attach-device my-guest ~/config/my-guest-hostdev.xml
-
-            The contents of my-guest-hostdev.xml:
-
-.. code-block:: xml
-
-            <hostdev mode='subsystem' type='mdev' managed='no' model='vfio-ap'>
-              <source>
-                <address uuid='62177883-f1bb-47f0-914d-32a22e3a8804'/>
-              </source>
-            </hostdev>
-
-
-   virsh qemu-monitor-command <guest-name> --hmp \
-   "device_add vfio-ap,sysfsdev=<path-to-mdev>,id=<device-id>"
-
-      For example, to hot plug the vfio_ap mediated device
-      62177883-f1bb-47f0-914d-32a22e3a8804 into the guest named 'my-guest' with
-      device-id hostdev0:
-
-      virsh qemu-monitor-command my-guest --hmp \
-      "device_add vfio-ap,\
-      sysfsdev=/sys/devices/vfio_ap/matrix/62177883-f1bb-47f0-914d-32a22e3a8804,\
-      id=hostdev0"
-
-2. A vfio_ap mediated device can be hot plugged by attaching the qemu monitor
-   to the guest and using the following qemu monitor command:
-
-      (qemu) device_add "vfio-ap,sysfsdev=<path-to-mdev>,id=<device-id>"
-
-      For example, to plug the vfio_ap mediated device
-      62177883-f1bb-47f0-914d-32a22e3a8804 into the guest with the device-id
-      hostdev0:
+Live Guest Migration
+====================
+The VFIO AP mediated device is not used to provide userspace with direct
+access to device memory as is the case with other devices that use the VFIO
+framework for device pass-through. Instead, it manages AP
+configuration metadata identifying the adapters, domains, and control
+domains to which a guest will be granted access. These AP resources are
+configured by assigning them to a vfio-ap mediated device via its sysfs
+assignment interfaces. When the guest is started, the vfio_ap device driver
+sets the guest's AP configuration from the metadata stored with the mediated
+device. The AP devices are not accessed directly through the vfio_ap driver,
+so the driver does not migrate the state of the AP devices themselves.
+Instead, it migrates the AP configuration metadata. The vfio_ap device
+driver on the destination host will then ensure that the AP configuration
+metadata migrated from the source host is compatible with the AP
+configuration available on the destination host and if
+so, will set the destination guest's AP configuration accordingly.
 
-         (QEMU) device-add "vfio-ap,\
-         sysfsdev=/sys/devices/vfio_ap/matrix/62177883-f1bb-47f0-914d-32a22e3a8804,\
-         id=hostdev0"
+To be considered compatible, the AP configuration for the destination host must
+meet these requirements:
+
+* Each AP adapter, domain and control domain number assigned to the source
+  guest's AP configuration must be in the destination host's AP
+  configuration. This can be verified as follows:
+
+  * On the source host, display the AP configuration of the source guest
+    with the following two commands:
+
+    .. code-block:: bash
+
+       cat /sys/devices/vfio_ap/matrix/$UUID/guest_matrix
+       cat /sys/devices/vfio_ap/matrix/$UUID/control_domains
+
+    .. note::
+       Replace ``$UUID`` with the actual UUID of your mediated device.
+
+       The ``guest_matrix`` lists the APQNs of the queue devices assigned
+       to the mediated device; for example:
+
+       .. code-block:: bash
+
+          00.0033
+          00.003a
+
+       The ``control_domains`` lists the domain numbers of the control
+       domains; for example:
+
+       .. code-block:: bash
+
+          0033
+          003a
+
+  * Display the AP configuration of the destination host with the following
+    two commands:
+
+    .. code-block:: bash
+
+       lszcrypt -V
+       cat /sys/bus/ap/ap_control_domain_mask
+
+    .. note::
+       The ``lszcrypt -V`` command lists the AP cards (adapters) and queue
+       devices on the host system; for example:
+
+       .. code-block:: bash
+
+          =========== ===== ============ ==========
+          CARD.DOMAIN TYPE  MODE         DRIVER
+          =========== ===== ============ ==========
+          00          CEX5C CCA-Coproc   cex4card
+          00.0033     CEX5C CCA-Coproc   vfio_ap
+          00.003a     CEX5C CCA-Coproc   vfio_ap
+          =========== ===== ============ ==========
+
+       Each bit in the ap_control_domain_mask corresponds to
+       domain numbers 0-255. If a bit is set to one, then
+       the control domain is available on the source host. For
+       example:
+
+       .. code-block:: bash
+
+          0x0000000000001020000000000000000000000000000000000000000000000000
+
+       This mask indicates that AP control domains 51 (0x33) and 58 (0x3a) are
+       in the AP configuration of the host system.
+
+  * Verify the configurations:
+
+    * Each APQN in the guest's sysfs ``guest_matrix`` file must match an
+      APQN returned from the ``lszcrypt -V`` command on the destination host. It
+      is important to note the driver to which the queue is bound which
+      is displayed in the ``driver`` column. Queues not bound to the vfio_ap
+      driver are not available to the destination guest. Even if the APQNs are
+      available to the driver, that does not guarantee they can be used by the
+      guest being migrated; for example, migration will fail if any of these APQNs
+      are assigned to a mediated device other than the one being migrated.
+
+    * Each domain number from the source guest's sysfs
+      ``control_domains`` attribute must correspond to a bit set to one in
+      the destination host's ``ap_control_domain_mask``.
+
+
+* Each APQN assigned to the source guest and destination guest must
+  reference a queue device with compatible hardware capabilities:
+
+  +--------------+---------------------------------------------------------------+
+  | Hardware     | Description                                                   |
+  | Capabilities |                                                               |
+  +==============+===============================================================+
+  | [1]          | * AP special command facility (APSC)                          |
+  | Facilities   | * AP 4096-bit ME PKU commands facility (AP4KM)                |
+  |              | * AP 4096-bit CRT PKU commands (AP4KC)                        |
+  +--------------+---------------------------------------------------------------+
+  | [1] Mode     | * CCA-mode                                                    |
+  |              | * Accelerator-mode                                            |
+  |              | * XCP-mode (EP11)                                             |
+  +--------------+---------------------------------------------------------------+
+  | [1] AP       |   APXA installed                                              |
+  | extended     |                                                               |
+  | addressing   |                                                               |
+  +--------------+---------------------------------------------------------------+
+  | [1] Command  |   Command filtering available                                 |
+  | filtering    |                                                               |
+  +--------------+---------------------------------------------------------------+
+  | [2]          | * Full native card function                                   |
+  | Functional   | * Only stateless functions                                    |
+  | capabilities |                                                               |
+  +--------------+---------------------------------------------------------------+
+  | [3] AP type  | * 10 (0x0a): CEX4                                             |
+  |              | * 11 (0x0b): CEX5                                             |
+  |              | * 12 (0x0c)  CEX6                                             |
+  |              | * 13 (0x0d)  CEX7                                             |
+  |              | * 14 (0x0e)  CEX8                                             |
+  +--------------+---------------------------------------------------------------+
+
+  +-----------------------------------------------------------------------------+
+  | Table Keys                                                                  |
+  +=============================================================================+
+  |                                                                             |
+  | [1]        The hardware capability must be the same for both the source     |
+  |            and destination queue device.                                    |
+  |                                                                             |
+  | [2]        The source and destination queues must either both have          |
+  |            full native card function or both have stateless functions.      |
+  |            If the functional capabilities don't match, then the source      |
+  |            queue can have stateless capabilities since full native card     |
+  |            function can handle stateless functions; otherwise, migration    |
+  |            will fail.                                                       |
+  |                                                                             |
+  | [3]        The AP type on the source and destination guests can             |
+  |            differ if the queue passed through to the target guest is a      |
+  |            newer model (backwards compatible)                               |
+  +-----------------------------------------------------------------------------+
+
+  * To verify the hardware capabilities are compatible:
+
+    * On both the source and destination hosts, display the hardware capabilities
+      for each AP adapter in the AP configuration for that host:
+
+      .. code-block:: bash
+
+         cat /sys/bus/ap/devices/card$APID/ap_functions
+
+      .. note::
+         The ``$APID`` is the two-character adapter number in hexadecimal format;
+         for example, ``card02`` or ``card1f``. The ``/sys/bus/ap/devices`` directory
+         also lists the APQNs of the queue devices installed in the respective
+         host system with the first two characters being the APID; for example:
+         ``02.0004`` or ``00.0033`` .
+
+    * Verify the hardware capabilities for each AP adapter device on the source
+      and destination host are compatible. The ``ap_functions`` attribute is a
+      bitmask. The bits in the mask read from left to right starting with bit 0.
+      Each bit that is set to one indicates the corresponding hardware capability
+      is installed:
+
+      * Bits 0-2 are the facilities bits. Each bit value must match for the AP
+        devices on the source and destination systems. The values indicate the
+        following:
+
+        * bit-0: APSC is installed
+        * bit-1: AP4KM is installed
+        * bit-2: AP4KC is installed
+
+      * Bits 3-5 specify the adapter Modes. Only one of these bits will be set to
+        one and must be the same for both the source and destination adapter
+        devices:
+
+        * bit-3: CCA-mode
+        * bit-4: Accelerator-mode
+        * bit-5: XCP-mode (EP11)
+
+      * Bit 6 specifies whether APXA is installed and must be the same for both
+        the source and destination adapter devices.
+
+      * Bit 7 specifies whether command filtering is installed
+        and must be the same for both the source and destination adapter devices.
+
+      * Bits 8-15 are the classification bits. There are only two relevant
+        bits and only one of them will be set to one. For the source and destination
+        adapter devices to be considered compatible:
+
+        * Bit 8 may be set to 1 on both hosts (full native card function)
+        * Bit 9 may be set to 1 on both hosts (only stateless functions available)
+        * Bit 9 may be set to 1 on the source host and bit 8 may be set to 1 on
+          the destination host
+
+      * Bits 16-17 are the binding state bits which must be 00
+
+  * To verify the AP types are compatible:
+
+    * On both the source and destination hosts, display the hardware type
+      for each AP adapter in the AP configuration for that host to ensure the
+      source and destination adapter types are the same, or the source type is
+      less than the destination type::
+
+       cat /sys/bus/ap/devices/card$APID/hwtype
+
+      .. note::
+         The ``$APID`` is the two-character adapter number in hexadecimal format;
+         for example, ``card02`` or ``card1f``.
+
+Setting up for live guest migration on the destination host
+-----------------------------------------------------------
+To set up a host as the destination for live guest migration, do the
+following:
+
+1. Create a mediated device
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Create a mediated device with the same name (UUID) as the mediated device
+used to supply the AP configuration to the source guest. For example, if
+the mediated device on the source guest is named
+62177883-f1bb-47f0-914d-32a22e3a8804:
+
+.. code-block:: bash
+
+   echo 62177883-f1bb-47f0-914d-32a22e3a8804 > \
+     /sys/devices/vfio_ap/matrix/mdev_supported_types/vfio_ap-passthrough/create
+
+2. Reserve adapters and domains for the vfio_ap device driver's use
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Reserve the same adapters, and domains passed through to the source guest
+for the vfio_ap device driver on the destination host by clearing the
+adapter numbers from the ``/sys/bus/ap/apmask`` and/or the domain numbers
+from the ``/sys/bus/ap/aqmask`` files.
+
+For example, suppose adapters 0, 20 (0x14) and 22 (0x16) as well as
+domains 51 (0x33) and 58 (0x3a) are passed through to the source guest. To
+ensure they can be passed through to the destination guest, they must be
+made available to the vfio_ap device driver on the destination host. To
+make them available, do one or both of the following on the destination host:
+
+.. code-block:: bash
+
+   echo -0,-0x14,-22 > /sys/bus/ap/apmask
+   echo -0,-0x33,-0x3a > /sys/bus/ap/aqmask
+
+.. note::
+
+    * It is not necessary to reserve both the adapters and domains.
+      Reserving an adapter implicitly allows the vfio_ap driver to assign
+      each of the domains available on the system along with the reserved
+      adapters to a guest's AP configuration and vice versa.
+
+    * The Cartesian product of the adapters and domains reserved for the
+      vfio_ap device driver identifies the APQNs of the AP queue devices to be
+      bound to the vfio_ap device driver. If an APQN does not reference a
+      queue device installed in the system at the time of live guest migration,
+      the migration will fail.
+
+    * It is not necessary to configure the destination mediated device with
+      adapters, domains and control domains because the source guest's AP
+      configuration will overlay the destination guest's during migration.
+
+    * To verify that the queue devices are reserved for the vfio_ap
+      device driver, issue the ``lszcrypt -V`` command and you should
+      see ``vfio_ap`` in the ``DRIVER`` column of the output.
+
+Live guest migration failures due to AP configuration errors
+------------------------------------------------------------
+This section describes the errors that may occur during live guest migration
+when the AP configuration of the source guest and destination host are not
+compatible and where to look for problem determination.
+
+The destination host is missing the mediated device
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+This error occurs when a mediated device with the same name (UUID) as the
+mediated device being migrated has not been created on the destination host.
+
+**Source host**
+
++--------------+----------------------------------------------------------------+
+| Log          | Message                                                        |
++==============+================================================================+
+| Console log: | error: device not found: mediated device '$UUID' not           |
+|              | found                                                          |
++--------------+----------------------------------------------------------------+
+| QEMU log:    | initiating migration                                           |
+|              | qemu-system-s390x: Sibling indicated error 1                   |
++--------------+----------------------------------------------------------------+
+
+.. note::
+   $UUID is the UUID of the mediated device being migrated from the source host.
+
+
+One or more queues are not bound to the vfio_ap driver on the destination host
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The queue devices passed through to the source guest are not installed in the
+destination host or are not bound to its vfio_ap device driver.
+
+**Source host**
+
++--------------+----------------------------------------------------------------+
+| Log          | Message                                                        |
++==============+================================================================+
+| Console log: | error: operation failed: migration failed. Message from the    |
+|              | source host: operation failed: job 'migration out' failed:     |
+|              | Sibling indicated error 1. Message from the destination host:  |
+|              | operation failed: job 'migration in' failed: load of migration |
+|              | failed: No such device: Failed to load vmstate version_id: 1,  |
+|              | ret: -19                                                       |
++--------------+----------------------------------------------------------------+
+
+**Destination host**
+
++--------------+----------------------------------------------------------------+
+| Kernel log:  | vfio_ap_mdev $UUID: Queue $APID.$APQI not available to         |
+|              | vfio_ap driver on target host                                  |
++--------------+----------------------------------------------------------------+
+| QEMU log:    | shutting down, reason=failed                                   |
+|              | qemu-system-s390x: terminating on signal $SIGNAL_NUM from      |
+|              | pid $PID $DAEMON                                               |
++--------------+----------------------------------------------------------------+
+
+
+One or more control domains are not available on the destination host
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The control domains passed through to the source guest are not installed on the
+destination host.
+
+**Source host**
+
++--------------+----------------------------------------------------------------+
+| Log          | Message                                                        |
++==============+================================================================+
+| Console log: | error: operation failed: migration failed. Message from the    |
+|              | source host: operation failed: job 'migration out' failed:     |
+|              | Sibling indicated error 1. Message from the destination host:  |
+|              | operation failed: job 'migration in' failed: load of migration |
+|              | failed: No such device: Failed to load vmstate version_id: 1,  |
+|              | ret: -19                                                       |
++--------------+----------------------------------------------------------------+
+
+**Destination host**
+
++--------------+----------------------------------------------------------------+
+| Kernel log:  | vfio_ap_mdev $UUID: Control domain $DOMAIN_NUM not available   |
+|              | on the destination host                                        |
++--------------+----------------------------------------------------------------+
+| QEMU log:    | shutting down, reason=failed                                   |
+|              | qemu-system-s390x: terminating on signal $SIGNAL_NUM from      |
+|              | pid $PID $DAEMON                                               |
++--------------+----------------------------------------------------------------+
+
+
+.. note::
+   * $UUID is the UUID of the mediated device being migrated from the source host.
+   * $APID.$APQI is adapter number and queue index (domain number) comprising the
+     $APQN (for example, 00.0033) of the queue device that is not available.
+   * $SIGNAL_NUM is the signal number that caused the QEMU process to terminate.
+   * $PID is the process ID of the QEMU process on the destination host.
+   * $DAEMON is the name of the QEMU daemon process.
+   * This message will be logged for each queue for which this error is detected.
+
+Failure to get hardware information for a queue device on destination host
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The vfio_ap device driver on the destination host will execute an AP instruction
+to get the hardware information for a queue device to perform queue compatibility
+checks. The instruction can fail for a number of reasons in which case the
+migration will be terminated.
+
+**Source host**
+
++--------------+----------------------------------------------------------------+
+| Log          | Message                                                        |
++==============+================================================================+
+| Console log: | error: operation failed: migration failed. Message from the    |
+|              | source host: operation failed: job 'migration out' failed:     |
+|              | Sibling indicated error 1. Message from the destination host:  |
+|              | operation failed: job 'migration in' failed: load of migration |
+|              | failed: failed to get hardware information for queue device    |
+|              | $APQN                                                          |
++--------------+----------------------------------------------------------------+
+
+**Destination host**
+
++--------------+----------------------------------------------------------------+
+| Log          | Message                                                        |
++==============+================================================================+
+| Console log: | vfio_ap_mdev $UUID: migration failed: Failed to get hwinfo for |
+|              | queue $APQN on target host: rc=$RESPONSE-CODE                  |
++--------------+----------------------------------------------------------------+
+| QEMU log:    | shutting down, reason=failed                                   |
+|              | qemu-system-s390x: terminating on signal $SIGNAL-ID from pid   |
+|              | $PID $DAEMON                                                   |
++--------------+----------------------------------------------------------------+
+
+.. note::
+   * $UUID is the UUID of the mediated device being migrated from the source host.
+   * $APQN (for example, 00.0033) of the queue device that is not compatible.
+   * $RESPONSE_CODE is the response code from the AP instruction.
+   * $SIGNAL_NUM is the signal number of the signal that caused the QEMU process
+     to terminate.
+   * $PID is the process ID of the QEMU process on the destination host.
+   * $DAEMON is the name of the QEMU daemon process.
+   * This message will be logged for each queue for which this error is detected.
+
+The AP configurations of the source guest and destination host not compatible
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The functional capabilities or facilities available on one or more of the queues
+passed through to the source guest are not compatible with the queue device with
+the same APQN on the destination system (see the Hardware Capabilities table above)
+
+**Source host**
+
++--------------+----------------------------------------------------------------+
+| Log          | Message                                                        |
++==============+================================================================+
+| Console log: | error: operation failed: migration failed. Message from the    |
+|              | source host: operation failed: job 'migration out' failed:     |
+|              | Sibling indicated error 1. Message from the destination host:  |
+|              | operation failed: job 'migration in' failed: load of migration |
+|              | failed: No such device: Failed to load vmstate version_id: 1,  |
+|              | ret: -19                                                       |
++--------------+----------------------------------------------------------------+
+| Kernel log:  | N/A                                                            |
++--------------+----------------------------------------------------------------+
+| QEMU log:    | *initiating migration*                                         |
+|              |                                                                |
+|              | *qemu-system-s390x: Sibling indicated error 1*                 |
++--------------+----------------------------------------------------------------+
+
+**Destination host**
+
++--------------+----------------------------------------------------------------+
+| Log          | Message                                                        |
++==============+================================================================+
+| Console log: | N/A                                                            |
++--------------+----------------------------------------------------------------+
+| Kernel log:  | *vfio_ap_mdev $UUID: Migration failed: Source and target       |
+|              | queue ($APQN) not compatible*                                  |
+|              |                                                                |
+|              | The message above will be followed by one or more messages     |
+|              | enumerating the incompatible features; for example:            |
+|              |                                                                |
+|              | ``vfio_ap_mdev $UUID: APSC facility installed in source queue  |
+|              | $APQN``                                                        |
+|              | ``vfio_ap_mdev $UUID: APSC facility not installed in target    |
+|              | queue $APQN``                                                  |
+|              |                                                                |
+|              | ``AP type of source ($APTYPE1) not compatible with target      |
+|              | ($APTYPE2)`` ...                                               |
++--------------+----------------------------------------------------------------+
+| QEMU log:    | *initiating migration*                                         |
+|              |                                                                |
+|              | *qemu-system-s390x: error while loading state section id ...*  |
+|              |                                                                |
+|              | *shutting down, reason=failed*                                 |
+|              |                                                                |
+|              | *terminating on signal $SIGNAL-ID from pid $PID $DAEMON*       |
++--------------+----------------------------------------------------------------+
+
+.. note::
+   * $UUID is the UUID of the mediated device being migrated from the source host.
+   * $APQN (for example, 00.0033) of the queue device that is incompatible.
+   * $APTYPE1 is the type of the source queue device.
+   * $APTYPE2 is the type of the target queue device.
+   * $SIGNAL-ID is the signal number of the signal that caused the QEMU process
+     to terminate.
+   * $PROCESS-ID is the process ID of the QEMU process on the source host.
+   * $PID is the process ID of the QEMU process on the destination host.
+   * $DAEMON is the name of the QEMU daemon process.
+   * Each follow-on message logging the incompatibility will be logged for each
+     error detected for the specified queue device.
+
+AP Configuration Management
+---------------------------
+The AP configurations of the source guest and destination host must be kept
+in synchronization or live guest migration will likely fail due to potential
+incompatibilities introduced by such changes. In particular, changing adapter
+or domain reservations via the sysfs ``apmask`` or ``aqmask`` attributes on
+either the source or destination host without coordinating such changes between
+the two hosts -especially while a migration is taking place - can result in
+migration failures.
+
+Configuration stability is an orchestration-layer or system administrator
+responsibility, which is consistent with other VFIO device types. The vfio_ap
+device driver will validate source and destination configurations and provide
+clear diagnostics when incompatibilities are detected, enabling orchestration
+tools to implement appropriate policies; for example, blocking migration when
+such changes are to be made.
+
+Master Key administration
+--------------------------
+It is imperative that s390 Common Cryptographic Architecture (CCA) master key
+administration be performed on both the source and destination AP
+devices to synchronize the key values prior to allowing live guest
+migration. If the master keys do not match, then crypto applications that
+rely on secure keys wrapped by a CCA master key will fail when the guest on
+which they are running is migrated to the destination host. Again, this is
+an orchestration-layer or system administrator responsibility and migration must
+be blocked while master key administration is being performed.
-- 
2.53.0

Re: [PATCH v6 01/15] s390/vfio-ap: Provide function to get the number of queues assigned to mdev

[sashiko-bot]

> Provides a function that returns the number of queues that are or will be
> passed through to a guest when the mdev is attached to a guest.
> 
> Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260727173239.2420754-1-akrowiak@linux.ibm.com?part=1

Re: [PATCH v6 02/15] s390/vfio-ap: Data structures for facilitating vfio device migration

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [Medium] The VFIO migration data structure lacks a magic identifier and version number, and relies on an architectural macro for array sizing, posing a risk to ABI stability.
- [Low] Typo and grammatical error in the docstring for `resuming_mig_file`.
--

--- Patch [2]: [PATCH v6 02/15] s390/vfio-ap: Data structures for facilitating vfio device migration ---
commit 1aa240c81b915a9ce3e59c82c532c41c1cab4d99
Author: Anthony Krowiak <akrowiak@linux.ibm.com>

s390/vfio-ap: Data structures for facilitating vfio device migration

This commit creates the data structures used to facilitate state transitions
during vfio device migration.

> diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
> new file mode 100644
> --- /dev/null
> +++ b/drivers/s390/crypto/vfio_ap_migration.c
[ ... ]
> +/**
> + * 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 the destination host:

[Severity: Low]
This isn't a bug, but there appears to be a missing word here. Should this
say "device on the destination host." instead of ending with a colon?

> + * @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 {
[ ... ]
> +/**
> + * struct vfio_ap_config - the guest's AP configuration
> + *
> + * @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				num_queues;
> +	u8				reserved[4];
> +	u64				adm[DIV_ROUND_UP(AP_DOMAINS, 64)];

[Severity: Medium]
Does this data structure need a version number or magic identifier to safely
handle ABI stability across host migrations?

Since this structure defines the binary layout of the migration data stream,
could changing the architectural macro AP_DOMAINS or the structure layout in 
future kernel versions silently break live migration compatibility between 
hosts running different kernel versions?

> +	struct vfio_ap_queue_info	qinfo[] __counted_by(num_queues);
> +};

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260727173239.2420754-1-akrowiak@linux.ibm.com?part=2

Re: [PATCH v6 03/15] s390/vfio-ap: Functions to initialize/release vfio device migration data

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider:

New issues:
- [High] The driver prematurely exposes the VFIO migration capability to userspace while only providing stub implementations that silently pretend to succeed.

Pre-existing issues:
- [High] The eventfd contexts for `req_trigger` and `cfg_chg_trigger` are leaked when the matrix mdev is removed or the device is closed.
- [Medium] In `vfio_ap_mdev_probe()`, the device is exposed to userspace before `req_trigger` and `cfg_chg_trigger` are initialized, allowing them to be clobbered by a concurrent ioctl.
--

--- Patch [3]: [PATCH v6 03/15] s390/vfio-ap: Functions to initialize/release vfio device migration data ---
commit faa8a565ea108d20c1807c07fbe1be6336a97435
Author: Anthony Krowiak <akrowiak@linux.ibm.com>

s390/vfio-ap: Functions to initialize/release vfio device migration data
    
Provides the functions that initialize and release the data structures
used during live guest migration.

> diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
> index fc3b2e154ad8b..ae0bd1f415feb 100644
> --- a/drivers/s390/crypto/vfio_ap_migration.c
> +++ b/drivers/s390/crypto/vfio_ap_migration.c

[ ... ]

> +static struct file *vfio_ap_set_state(struct vfio_device *vdev,
> +				      enum vfio_device_mig_state  new_state)
> +{
> +	return NULL;
> +}

[Severity: High]
Does returning NULL unconditionally here trick the VFIO FSM into believing the
state transition succeeded immediately without actually transferring any data?

[ ... ]

> +void vfio_ap_init_migration_capabilities(struct ap_matrix_mdev *matrix_mdev)
> +{
> +	if (ap_is_se_guest())
> +		return;
> +
> +	matrix_mdev->vdev.migration_flags = VFIO_MIGRATION_STOP_COPY;
> +	matrix_mdev->vdev.mig_ops = &vfio_ap_migration_ops;
> +}

[Severity: High]
Since the state transition operations like vfio_ap_set_state() currently just
return NULL, does advertising the VFIO_MIGRATION_STOP_COPY capability here
prematurely expose an incomplete migration implementation to userspace, which
could result in broken live migration and guest data corruption?

> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index 36786d70a88f5..90b0fce0123b5 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c

[ ... ]

> +static void vfio_ap_mdev_release_dev(struct vfio_device *vdev)
> +{
> +	struct ap_matrix_mdev *matrix_mdev;
> +
> +	mutex_lock(&matrix_dev->mdevs_lock);
> +	matrix_mdev = container_of(vdev, struct ap_matrix_mdev, vdev);
> +	vfio_ap_release_migration_data(matrix_mdev);
> +	mutex_unlock(&matrix_dev->mdevs_lock);
> +}

[Severity: High]
This isn't a bug introduced by this patch, but does vfio_ap_mdev_release_dev()
fail to put the req_trigger and cfg_chg_trigger eventfd contexts? 

If they are also not cleaned up in vfio_ap_mdev_close_device(), could this
allow a user to systematically leak kernel memory by repeatedly opening the
device, configuring IRQs, and closing it?

[ ... ]

>  	ret = vfio_register_emulated_iommu_dev(&matrix_mdev->vdev);
>  	if (ret)
>  		goto err_put_vdev;
> +
> +	mutex_lock(&matrix_dev->mdevs_lock);
>  	matrix_mdev->req_trigger = NULL;
>  	matrix_mdev->cfg_chg_trigger = NULL;

[Severity: Medium]
This isn't a bug introduced by this patch, but does assigning NULL to
req_trigger and cfg_chg_trigger here risk clobbering valid pointers?

If a concurrent ioctl configures the triggers via VFIO_DEVICE_SET_IRQS
immediately after the device is exposed via vfio_register_emulated_iommu_dev(),
but before we acquire mdevs_lock here, could we overwrite the initialized
triggers and leak the eventfd contexts?

>  	dev_set_drvdata(&mdev->dev, matrix_mdev);
> -	mutex_lock(&matrix_dev->mdevs_lock);
>  	list_add(&matrix_mdev->node, &matrix_dev->mdev_list);
>  	mutex_unlock(&matrix_dev->mdevs_lock);
>  	return 0;

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260727173239.2420754-1-akrowiak@linux.ibm.com?part=3

Re: [PATCH v6 04/15] s390/vfio-ap: Reset migration state in VFIO_DEVICE_RESET ioctl handler

[sashiko-bot]

> According to the VFIO migration specifications, userspace must issue a
> VFIO_DEVICE_RESET ioctl if a vfio device enters an error state or fails a
> state transition to recover the device and return its migration state to
> RUNNING. This patch adds a function that is called when a VFIO_DEVICE_RESET
> is issued that releases the migration files and frees the storage allocated
> for maintaining the migration state.
> 
> Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260727173239.2420754-1-akrowiak@linux.ibm.com?part=4

Re: [PATCH v6 05/15] s390-vfio-ap: Callback to get/set vfio device mig state during guest migration

[sashiko-bot]

> Implements two callbacks related to the current state of a vfio-ap device:
> * The callback that sets a new migration state of a vfio-ap device during
>   live migration of guests with pass-through access to AP devices. This
>   callback is mandatory for VFIO_DEVICE_FEATURE_MIGRATION support.
> 
>   The function pointer for this callback is specified via the
>   'migration_set_state' field of the 'vfio_migration_ops' structure
>   which is stored with the VFIO device when the 'vfio_device'
>   structure representing the mediated device is initialized.
> 
> * The callback that returns the current vfio device migration state during
>   live migration of guests with pass-through access to AP devices.
> 
>   The function pointer for this callback is specified via the
>   'migration_get_state' field of the 'vfio_migration_ops' structure
>   which is stored with the VFIO device when the 'vfio_device'
>   structure representing the mediated device is initialized.
> 
> Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260727173239.2420754-1-akrowiak@linux.ibm.com?part=5

Re: [PATCH v6 06/15] s390/vfio-ap: Transition guest migration state from STOP to STOP_COPY

[sashiko-bot]

> The transition of the guest migration state from VFIO_DEVICE_STATE_STOP to
> VFIO_DEVICE_STATE_STOP_COPY begins the process of saving the
> vfio device state. The vfio device state is comprised of the guest's
> AP configuration which specifies the adapters, domains and control
> domains to which the guest will be given access.
> 
> To begin the process of saving the vfio device state, the VFIO AP device
> driver opens a file stream that will be used to read the source guest's
> AP configuration.
> 
> Note:
> This commit introduces the file operations structure for migration state
> files with a stub implementation of the read operation. The complete
> implementation is provided in the subsequent commit.
> 
> This incremental approach allows for easier review of the migration
> infrastructure setup separate from the actual implementation logic.
> 
> Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260727173239.2420754-1-akrowiak@linux.ibm.com?part=6

Re: [PATCH v6 07/15] s390/vfio-ap: File ops called to save the vfio device migration state

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 4 potential issue(s) to consider:
- [Critical] Pointer casting a 64-bit uninitialized `unsigned long` to a 32-bit `int *` on a big-endian architecture leaves the lower 32 bits uninitialized, leading to massive buffer overflows or a `__counted_by` trap.
- [High] Dropping `mdevs_lock` before `copy_to_user()` opens a TOCTOU race window that allows concurrent freeing of the `ap_config` buffer and `mig_data`, causing a double Use-After-Free.
- [High] The global `mdevs_lock` is held across potentially tens of thousands of slow hardware instructions, explicitly contradicting documented subsystem design and risking host soft lockups.
- [High] The `.read` callback unconditionally rejects all standard read operations because it erroneously assumes the `pos` pointer is NULL.
--

--- Patch [7]: [PATCH v6 07/15] s390/vfio-ap: File ops called to save the vfio device migration state ---
commit 6828e02e20841803a7c3d24379ed9d9979222d55
Author: Anthony Krowiak <akrowiak@linux.ibm.com>

s390/vfio-ap: File ops called to save the vfio device migration state

This commit implements the read callback function for the vfio-ap device
migration state file. It copies the guest's AP configuration and hardware
queue information to userspace when the device transitions to the STOP_COPY
state.

> --- a/drivers/s390/crypto/vfio_ap_migration.c
> +++ b/drivers/s390/crypto/vfio_ap_migration.c

[ ... ]

> +static int vfio_ap_store_queue_info(const char *mdev_name,
> +				    struct vfio_ap_config *ap_config)
> +{
> +	struct ap_tapq_hwinfo source_hwinfo;
> +	unsigned long num_queues;
> +	int ret;
> +
> +	/*
> +	 * ap_tapq() is a hardware instruction that may take time to complete.
> +	 * It must be called without mdevs_lock held to avoid blocking other
> +	 * mdevs. The apqn list was already snapshotted into ap_config->qinfo[]
> +	 * by the caller under the lock.
> +	 */
> +	for (num_queues = 0; num_queues < ap_config->num_queues; num_queues++) {
> +		ret = get_hardware_info_for_queue(mdev_name, &source_hwinfo,
> +						  ap_config->qinfo[num_queues].apqn);

[Severity: High]
Does this loop actually execute with the mdevs_lock held, despite the
comment?

Looking at the call chain, vfio_ap_stop_copy_read() acquires
matrix_dev->mdevs_lock and calls vfio_ap_get_config(), which asserts
the lock is held and then calls vfio_ap_store_queue_info().

Since the lock is never dropped in this chain, will executing PQAP(TAPQ)
in a loop for potentially many queues block other mdev operations across
the host?

[ ... ]

> +static int vfio_ap_get_config(struct ap_matrix_mdev *matrix_mdev)
> +{
> +	unsigned long *apm, *aqm, apid, apqi, num_queues;
> +	struct vfio_ap_config *ap_configuration;
> +	const char *mdev_name;
> +	size_t ap_config_size;
> +	int ret;
> +
> +	lockdep_assert_held(&matrix_dev->mdevs_lock);
> +
> +	ap_config_size = vfio_ap_config_size(matrix_mdev, (int *)&num_queues);
> +
> +	ap_configuration = kzalloc(ap_config_size, GFP_KERNEL_ACCOUNT);
> +	if (!ap_configuration)
> +		return -ENOMEM;
> +
> +	/*
> +	 * num_queues must be set before writing qinfo[] elements; the
> +	 * __counted_by(num_queues) annotation on qinfo[] causes the compiler to
> +	 * insert bounds checks that evaluate against ap_configuration->num_queues.
> +	 * Writing through qinfo[i] with num_queues still 0 would trap.
> +	 */
> +	ap_configuration->num_queues = num_queues;

[Severity: Critical]
Can casting the uninitialized 8-byte unsigned long num_queues to an
int pointer cause uninitialized memory issues on big-endian systems?

On s390x, writing a 32-bit integer to an 8-byte address only initializes
the most significant 4 bytes, leaving the least significant 4 bytes as
stack garbage.

When ap_configuration->num_queues (a u32) is assigned num_queues, will it
truncate the 8-byte value, completely discarding the initialized high
bytes and storing the uninitialized garbage data? Could this lead to
out-of-bounds accesses in the array bounds checks?

[ ... ]

> +static ssize_t vfio_ap_stop_copy_read(struct file *filp, char __user *buf,
> +				      size_t len, loff_t *pos)
> +{
> +	struct vfio_ap_migration_file *mig_file;
> +	struct ap_matrix_mdev *matrix_mdev;
> +	loff_t read_pos;
> +	ssize_t ret;
> +
> +	/*
> +	 * When userspace calls read() with an explicit offset (pread), pos is
> +	 * non-NULL and the function rejects it with -ESPIPE (illegal seek). For
> +	 * normal read() calls, pos is NULL, so we'll use the file's internal
> +	 * position filp->f_pos
> +	 */
> +	if (pos)
> +		return -ESPIPE;

[Severity: High]
Is the assumption that pos is NULL for normal read() calls correct?

The VFS layer unconditionally passes a valid, non-NULL loff_t pointer
(pointing to a local stack variable) to the .read callback for standard
reads. Will this check unconditionally reject all standard read operations
on the migration state file?

[ ... ]

> +	/*
> +	 * Drop the lock only for the copy_to_user().  The ap_config buffer is
> +	 * stable: it is allocated once in vfio_ap_get_config() and freed only
> +	 * in vfio_ap_release_mig_files() / vfio_ap_release_stop_copy_file(),
> +	 * both of which require mdevs_lock.  Since we already advanced *pos
> +	 * above, no other thread will compute an overlapping region.
> +	 */
> +	mutex_unlock(&matrix_dev->mdevs_lock);
> +
> +	if (copy_to_user(buf, (char *)mig_file->ap_config + read_pos, len))
> +		return -EFAULT;
> +
> +	return len;
> +}

[Severity: High]
Could dropping mdevs_lock here open a race condition that leads to a
use-after-free?

If a concurrent thread triggers a device close or reset (for example,
via VFIO_DEVICE_RESET) while this thread is at the copy_to_user() call,
the reset path could acquire mdevs_lock and free both the ap_config
buffer and the mig_data struct.

Since mig_file is a pointer into mig_data, will dereferencing it here to
access ap_config cause a double use-after-free, copying freed memory to
userspace?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260727173239.2420754-1-akrowiak@linux.ibm.com?part=7

Re: [PATCH v6 09/15] s390/vfio-ap: Add method to set a new guest AP configuration

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Latent NULL pointer dereference in `collect_queues_by_apid` due to contradictory logic.
--

--- Patch [9]: [PATCH v6 09/15] s390/vfio-ap: Add method to set a new guest AP configuration ---
commit 5b979f09ef9429e09eace5977dabbd22cc832bbf
Author: Anthony Krowiak <akrowiak@linux.ibm.com>

s390/vfio-ap: Add method to set a new guest AP configuration

This commit adds a new vfio_ap_set_new_config function to set a guest's AP
configuration. It refactors code from ap_config_store to handle changes to
the sysfs ap_config attribute and support live guest migration.

> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index d05372b50d2fc..0b49be22d5d8b 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c

[ ... ]

> -static void collect_queues_to_reset(struct ap_matrix_mdev *matrix_mdev,
> -				    unsigned long apid,
> -				    struct list_head *qlist)
> +static void collect_queues_by_apid(struct ap_matrix_mdev *matrix_mdev,
> +				   unsigned long apid,
> +				   struct list_head *qlist)
>  {
>  	struct vfio_ap_queue *q;
>  	unsigned long  apqi;
>  
>  	for_each_set_bit_inv(apqi, matrix_mdev->shadow_apcb.aqm, AP_DOMAINS) {
> -		q = vfio_ap_mdev_get_queue(matrix_mdev, AP_MKQID(apid, apqi));
> +		q = matrix_mdev ?
> +				vfio_ap_mdev_get_queue(matrix_mdev, AP_MKQID(apid, apqi)) :
> +				vfio_ap_find_queue(AP_MKQID(apid, apqi));

[Severity: Medium]
Will this result in a NULL pointer dereference if matrix_mdev is NULL?

The loop condition unconditionally accesses matrix_mdev->shadow_apcb.aqm.
However, the ternary operator inside the loop (matrix_mdev ?) suggests
that matrix_mdev could be NULL. 

If matrix_mdev can indeed be NULL, the unconditional dereference in 
for_each_set_bit_inv() will crash before the check is evaluated. If 
matrix_mdev is never NULL in practice, is the ternary check necessary?

>  		if (q)
>  			list_add_tail(&q->reset_qnode, qlist);
>  	}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260727173239.2420754-1-akrowiak@linux.ibm.com?part=9

Re: [PATCH v6 10/15] s390/vfio-ap: File ops called to resume the vfio device migration

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 4 potential issue(s) to consider:
- [Critical] Double fetch vulnerability in the resuming write path allows out-of-bounds kernel reads.
- [Critical] Use-After-Free during concurrent device teardown while executing copy_from_user.
- [High] Lack of rate limiting in validation error paths allows userspace to flood the kernel log and cause a Denial of Service.
- [High] Unsynchronized concurrent writes can trigger premature configuration validation on uninitialized memory.
--

--- Patch [10]: [PATCH v6 10/15] s390/vfio-ap: File ops called to resume the vfio device migration ---
commit 56776518d352cfe0d799d4f95bc7d9c8703337bf
Author: Anthony Krowiak <akrowiak@linux.ibm.com>
Subject: s390/vfio-ap: File ops called to resume the vfio device migration

This commit implements the write callback for the vfio-ap device migration
file stream. It restores the source guest's AP configuration by validating
and hot-plugging it into the destination guest.

> diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
> index c7fecad0b6769..c12ba82ec5277 100644
> --- a/drivers/s390/crypto/vfio_ap_migration.c
> +++ b/drivers/s390/crypto/vfio_ap_migration.c

[ ... ]

> @@ -881,14 +881,20 @@
>  static void report_qinfo_incompatibilities(const char *mdev_name,
>  					   unsigned long apqn,
>  					   struct ap_tapq_hwinfo *src_hwinfo,
>  					   struct ap_tapq_hwinfo *target_hwinfo)
>  {
> +	pr_err("vfio_ap_mdev %s: Migration failed: Source and target queue (%02lx.%04lx) not compatible\n",
> +	       mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));

[Severity: High]
Is it possible for userspace to flood the kernel log here?

If a configuration with a large number of incompatible queues is provided,
verify_ap_configs_are_compatible() continues processing rather than aborting.

Since report_qinfo_incompatibilities() and its helpers issue unconditional
pr_err() calls for each mismatch, could this cause CPU stalls or a denial
of service?

> +
> +	report_facilities_compatibility(mdev_name, apqn, src_hwinfo, target_hwinfo);
> +	report_mode_compatibility(mdev_name, apqn, src_hwinfo, target_hwinfo);

[ ... ]

> @@ -1071,61 +1071,80 @@
>  static ssize_t vfio_ap_resuming_write(struct file *filp, const char __user *buf,
>  				      size_t len, loff_t *pos)
>  {

[ ... ]

> +	/*
> +	 * Snapshot and advance *pos under the lock before dropping it for
> +	 * copy_from_user().  This prevents concurrent write()s on the same
> +	 * stream file from computing the same destination offset and clobbering
> +	 * each other's data or racing to reassign mig_data->resuming_mig_file.
> +	 */
> +	write_pos = *pos;
> +	*pos += len;
> +
> +	mutex_unlock(&matrix_dev->mdevs_lock);
> +
> +	if (copy_from_user((char *)ap_config + write_pos, buf, len)) {
> +		if (new_allocation)
> +			kvfree(ap_config);
> +		return -EIO;
> +	}

[Severity: Critical]
Can a concurrent device teardown cause a use-after-free here?

The mdevs_lock is dropped to perform copy_from_user(). If a concurrent
thread closes the VFIO device, vfio_ap_release_mig_files() will call
kvfree(mig_data->resuming_mig_file.ap_config). Would this result in
copy_from_user() writing into freed kernel memory?

[Severity: Critical]
Could this sequence introduce a double-fetch vulnerability?

The first fetch in allocate_ap_config() reads num_queues to determine the
allocation size. The lock is then dropped, and this second copy_from_user()
overwrites the entire buffer, including the num_queues field.

If userspace modifies num_queues between these fetches, could it inflate
ap_config->num_queues beyond the allocated size, causing out-of-bounds
reads in queues_available() when it loops over source_config->num_queues?

> +
> +	/* Check if we've completed writing the entire configuration */
> +	if (write_pos + len == cfg_sz) {
> +		/*
> +		 * do_post_copy_validation() calls ap_tapq() which is a slow
> +		 * hardware instruction.  Run it before acquiring the update
> +		 * locks to avoid holding guests_lock, kvm->lock, and
> +		 * mdevs_lock across the hardware calls.
> +		 */
> +		ret = do_post_copy_validation(mdev_name, ap_config);

[Severity: High]
Does this completion check safely handle concurrent writes?

If userspace issues asynchronous write() syscalls for different chunks of
the payload, they might execute copy_from_user() concurrently. If the
thread writing the final chunk completes its copy before threads writing
earlier chunks finish theirs, could do_post_copy_validation() be called
on a buffer that still contains uninitialized data?

> +		if (ret < 0) {
> +			if (new_allocation)
> +				kvfree(ap_config);
> +			return ret;
> +		}

[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260727173239.2420754-1-akrowiak@linux.ibm.com?part=10

Re: [PATCH v6 08/15] s390/vfio-ap: Transition device migration state from STOP to RESUMING

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [Critical] Use-After-Free in `vfio_ap_stop_copy_read` leading to kernel memory leak to userspace.
- [Low] The `.release` callback logic for cleaning up the resuming and stop-copy file states is completely unreachable dead code.
--

--- Patch [8]: [PATCH v6 08/15] s390/vfio-ap: Transition device migration state from STOP to RESUMING ---
commit 798f82863e85b4d37fd3594dc855fe7caaaaf7f5
Author: Anthony Krowiak <akrowiak@linux.ibm.com>

s390/vfio-ap: Transition device migration state from STOP to RESUMING

Transitioning from VFIO_DEVICE_STATE_STOP to VFIO_DEVICE_STATE_RESUMING
starts a process of restoring the device state of the vfio device on the
target system. To prepare for restoring the device state, open a file
stream to receive the guest's AP configuration saved when the device state
on the source system transitioned from VFIO_DEVICE_STATE_STOP to
VFIO_DEVICE_STATE_STOP_COPY.

> diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
> index e4bc67b1eb842..c7fecad0b6769 100644
> --- a/drivers/s390/crypto/vfio_ap_migration.c
> +++ b/drivers/s390/crypto/vfio_ap_migration.c

[ ... ]

> @@ -99,6 +108,8 @@ static int vfio_ap_release_mig_file(struct inode *file_inode, struct file *filp)
>  
>  	if (filp == matrix_mdev->mig_data->stop_copy_mig_file.filp)
>  		vfio_ap_release_stop_copy_file(matrix_mdev->mig_data);
> +	else if (filp == matrix_mdev->mig_data->resuming_mig_file.filp)
> +		vfio_ap_release_resuming_file(matrix_mdev->mig_data);

[Severity: Low]
Is this conditional branch actually reachable?

During vfio_ap_open_file_stream(), the driver takes an internal reference to
the file via get_file(). This means the VFS .release callback is only invoked
after the driver explicitly drops its reference by calling fput().

If fput() is called in vfio_ap_release_mig_files(), which first sets
mig_data->resuming_mig_file.filp = NULL, won't filp inside mig_data always
be NULL by the time this .release callback executes?

Consequently, will this check always evaluate to false, leaving
vfio_ap_release_resuming_file() as unused dead code?

[ ... ]

> @@ -400,6 +411,26 @@ static struct file *vfio_ap_open_file_stream(struct ap_matrix_mdev *matrix_mdev,
>  	return filp;
>  }
>  
> +static ssize_t vfio_ap_resuming_write(struct file *filp, const char __user *buf,
> +				      size_t len, loff_t *pos)
> +{
> +	/* TODO */
> +	return -EOPNOTSUPP;
> +}
> +
> +static const struct file_operations vfio_ap_resume_fops = {
> +	.owner = THIS_MODULE,
> +	.write = vfio_ap_resuming_write,
> +	.release = vfio_ap_release_mig_file,
> +};

[Severity: Critical]
Could the migration file stream logic be vulnerable to a use-after-free when
the device file descriptor is concurrently closed?

Looking at the related vfio_ap_stop_copy_read() stream implementation, it
drops mdevs_lock before calling copy_to_user():

drivers/s390/crypto/vfio_ap_migration.c:vfio_ap_stop_copy_read() {
    ...
    mutex_unlock(&matrix_dev->mdevs_lock);

    if (copy_to_user(buf, (char *)mig_file->ap_config + read_pos, len))
        return -EFAULT;
    ...
}

If the device file descriptor is concurrently closed, vfio_ap_mdev_release()
could invoke vfio_ap_release_migration_data(), which acquires mdevs_lock and
frees the mig_data structure. 

When vfio_ap_stop_copy_read() resumes, will it dereference the freed mig_data
structure via mig_file->ap_config and leak kernel memory to userspace?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260727173239.2420754-1-akrowiak@linux.ibm.com?part=8

Re: [PATCH v6 13/15] s390/vfio-ap: Callback to get the size of data to be migrated during guest migration

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] Logic duplication for calculating the configuration size.
--

--- Patch [13]: [PATCH v6 13/15] s390/vfio-ap: Callback to get the size of data to be migrated during guest migration ---
commit f0e78a002713b19ca67967cef71fbd73dea59ee7
Author: Anthony Krowiak <akrowiak@linux.ibm.com>

s390/vfio-ap: Callback to get the size of data to be migrated during guest migration

This commit adds the mandatory migration_get_data_size callback for VFIO
migration support on the s390 vfio_ap driver. The callback calculates the
estimated data length required to migrate the device's internal state.

> diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
> index 1c385908fc39b..8379cf8bbce89 100644
> --- a/drivers/s390/crypto/vfio_ap_migration.c
> +++ b/drivers/s390/crypto/vfio_ap_migration.c
> @@ -1392,7 +1392,18 @@ static int vfio_ap_get_state(struct vfio_device *vdev,
>  static int vfio_ap_get_data_size(struct vfio_device *vdev,
>  				 unsigned long *stop_copy_length)
>  {
> -	return -EOPNOTSUPP;
> +	struct ap_matrix_mdev *matrix_mdev;
> +	size_t qinfo_sz;
> +	int num_queues;
> +
> +	mutex_lock(&matrix_dev->mdevs_lock);
> +	matrix_mdev = container_of(vdev, struct ap_matrix_mdev, vdev);
> +	num_queues = vfio_ap_mdev_get_num_queues(&matrix_mdev->shadow_apcb);
> +	qinfo_sz = num_queues * sizeof(struct vfio_ap_queue_info);
> +	*stop_copy_length = qinfo_sz + sizeof(struct vfio_ap_config);

[Severity: Low]
Does this code manually duplicate the size calculation logic already present 
in the existing static helper vfio_ap_config_size() within this same file?

Additionally, since struct vfio_ap_config uses a trailing flexible array 
member for qinfo, would it be better to use the standard struct_size() macro 
to compute the total length instead of manual multiplication and addition?

> +	mutex_unlock(&matrix_dev->mdevs_lock);
> +
> +	return 0;
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260727173239.2420754-1-akrowiak@linux.ibm.com?part=13

Re: [PATCH v6 11/15] s390/vfio-ap: Transition device migration state to STOP

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 4 potential issue(s) to consider:
- [Critical] Dropping mdevs_lock during copy_to_user and copy_from_user in migration data transfers allows concurrent device reset or close to free the ap_config buffer, leading to an exploitable Use-After-Free.
- [Critical] A double fetch of the userspace configuration buffer allows a malicious user to modify the num_queues field after size allocation, leading to an Out-Of-Bounds (OOB) heap read and unauthorized hardware access.
- [High] Permanent leak of migration file streams, ap_config buffers, and VFIO device registration references due to missing fput() when transitioning to the STOP state.
- [High] The mdevs_lock is held while calling ap_tapq(), a slow hardware instruction, violating the stated subsystem locking rules and risking host stalls.
--

--- Patch [11]: [PATCH v6 11/15] s390/vfio-ap: Transition device migration state to STOP ---
commit bf4a9d5f155b1c98e5568129336b12baad5821b5
Author: Anthony Krowiak <akrowiak@linux.ibm.com>

s390/vfio-ap: Transition device migration state to STOP

This commit updates the device migration state machine for vfio-ap to properly
handle the transition to the STOP state. Since there is no physical direct
memory access device virtualized by vfio-ap, the state transition logic now
terminates the data transfer session by returning NULL.

> diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
> index c12ba82ec5277..fc4cb893f0f00 100644
> --- a/drivers/s390/crypto/vfio_ap_migration.c
> +++ b/drivers/s390/crypto/vfio_ap_migration.c
> @@ -1267,12 +1267,17 @@ vfio_ap_transition_to_state(struct ap_matrix_mdev *matrix_mdev,
>  		return filp;
>  	}
>  
> +	/*
> +	 * Terminates the data transfer session of the vfio-ap device state
> +	 * between the source and target hosts. Since the vfio-ap device does
> +	 * not virtualize a DMA device, there is no internal device state to
> +	 * incorporate into the vfio-ap device on the target.
> +	 */
>  	if ((cur_state == VFIO_DEVICE_STATE_RESUMING &&
>  	     new_state == VFIO_DEVICE_STATE_STOP) ||
>  	    (cur_state == VFIO_DEVICE_STATE_STOP_COPY &&
>  	     new_state == VFIO_DEVICE_STATE_STOP)) {
> -		/* TODO */
> -		return ERR_PTR(-EOPNOTSUPP);
> +		return NULL;

[Severity: High]
Does returning NULL here permanently leak the migration file streams and
associated data?

When the state transitions to STOP, vfio_ap_transition_to_state() returns
NULL without relinquishing the driver's extra file reference. The driver
previously takes this extra reference in vfio_ap_open_file_stream():

drivers/s390/crypto/vfio_ap_migration.c:vfio_ap_open_file_stream() {
    ...
	get_file(filp);

	return filp;
}

If this reference isn't dropped, wouldn't we leak memory (struct file,
ap_config buffers, anonymous inodes) and vfio device registration pins?
This regression might potentially lead to resource exhaustion or prevent
device unbinding.

>  	}
>  
>  	if ((cur_state == VFIO_DEVICE_STATE_STOP &&

[Severity: Critical]
Can dropping mdevs_lock during copy operations lead to an exploitable
use-after-free regression?

In both vfio_ap_stop_copy_read() and vfio_ap_resuming_write(), the
mdevs_lock is explicitly dropped while a pointer to the ap_config buffer
is passed to copy_to_user() or copy_from_user():

drivers/s390/crypto/vfio_ap_migration.c:vfio_ap_stop_copy_read() {
    ...
	mutex_unlock(&matrix_dev->mdevs_lock);

	if (copy_to_user(buf, (char *)mig_file->ap_config + read_pos, len))
    ...
}

Concurrently, if another thread issues a vfio device reset ioctl,
couldn't vfio_ap_reset_migration_state() acquire mdevs_lock and
synchronously free the ap_config buffers via vfio_ap_release_mig_files()?
The copy operations would then proceed using the freed heap pointer.

[Severity: Critical]
Does this code allow an out-of-bounds heap read due to a double fetch of
the userspace configuration buffer?

In vfio_ap_resuming_write(), allocate_ap_config() performs an initial
copy_from_user() to determine num_queues and allocate the struct:

drivers/s390/crypto/vfio_ap_migration.c:vfio_ap_resuming_write() {
    ...
		ret = allocate_ap_config(&ap_config, buf, len);
    ...
}

Immediately afterward, vfio_ap_resuming_write() performs a second
copy_from_user() using the same unvalidated userspace buffer pointer:

    ...
	if (copy_from_user((char *)ap_config + write_pos, buf, len)) {
    ...

If a malicious user modifies the num_queues field between these fetches,
could the artificially inflated count cause an out-of-bounds read in
setup_ap_matrix_from_ap_config():

drivers/s390/crypto/vfio_ap_migration.c:setup_ap_matrix_from_ap_config() {
    ...
	for (int i = 0; i < ap_config->num_queues; i++) {
		qinfo = ap_config->qinfo[i];
		apid = AP_QID_CARD(qinfo.apqn);
    ...
}

and use it to grant unauthorized hardware access to the guest?

[Severity: High]
Are we holding mdevs_lock while executing a slow hardware instruction?

The ap_tapq() instruction is called in a loop within
vfio_ap_store_queue_info(), which includes a comment stating it must be
called without mdevs_lock held:

drivers/s390/crypto/vfio_ap_migration.c:vfio_ap_store_queue_info() {
    ...
	/*
	 * ap_tapq() is a hardware instruction that may take time to complete.
	 * It must be called without mdevs_lock held to avoid blocking other
	 * mdevs. The apqn list was already snapshotted into ap_config->qinfo[]
	 * by the caller under the lock.
	 */
	for (num_queues = 0; num_queues < ap_config->num_queues; num_queues++) {
		ret = get_hardware_info_for_queue(mdev_name, &source_hwinfo,
						  ap_config->qinfo[num_queues].apqn);
    ...
}

However, the call chain vfio_ap_stop_copy_read() -> vfio_ap_get_config()
explicitly takes mdevs_lock, asserts it, and then invokes
vfio_ap_store_queue_info() directly while still holding the mutex:

drivers/s390/crypto/vfio_ap_migration.c:vfio_ap_stop_copy_read() {
    ...
	mutex_lock(&matrix_dev->mdevs_lock);
    ...
	if (!mig_file->ap_config) {
		ret = vfio_ap_get_config(matrix_mdev);
    ...
}

Could this regression stall other mdev operations on the host and cause a
potential denial of service?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260727173239.2420754-1-akrowiak@linux.ibm.com?part=11

Re: [PATCH v6 15/15] s390/vfio-ap: Add live guest migration chapter to vfio-ap.rst

[sashiko-bot]

> Add a 'Live Guest Migration' chapter to the
> Documentation/arch/s390/vfio-ap.rst document to describe the details for
> initiating live guest migration for a guest to which AP adapters, domains
> and control domains have been passed through.
> 
> Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260727173239.2420754-1-akrowiak@linux.ibm.com?part=15

Re: [PATCH v6 12/15] s390/vfio-ap: Transition device migration state from STOP to RUNNING and vice versa

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [Critical] Concurrent device reset, closure, or state transitions during migration data transfer cause Use-After-Free or Write-After-Free of `ap_config`.
- [High] Overwriting the active migration file descriptor during state transitions allows silent migration of stale state and leaks file references.
--

--- Patch [12]: [PATCH v6 12/15] s390/vfio-ap: Transition device migration state from STOP to RUNNING and vice versa ---
commit 2b837152c9f64c5082507b5aa41ffc56027c1e29
Author: Anthony Krowiak <akrowiak@linux.ibm.com>

s390/vfio-ap: Transition device migration state from STOP to RUNNING and vice versa

The transition from STOP to RUNNING and vice versa indicates that
the vfio device is operating normally and migration is not
currently taking place. In this case, just set the new state.

> diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
> index fc4cb893f0f00..1c385908fc39b 100644
> --- a/drivers/s390/crypto/vfio_ap_migration.c
> +++ b/drivers/s390/crypto/vfio_ap_migration.c
> @@ -1280,12 +1280,17 @@ vfio_ap_transition_to_state(struct ap_matrix_mdev *matrix_mdev,
[ ... ]
> +	/*
> +	 * These states indicate migration has either not been initiated or
> +	 * has completed and the vfio-ap device is operating normally. Since the
> +	 * vfio-ap device does not virtualize a DMA device, there is no internal
> +	 * device state to incorporate into the vfio-ap device on the target.
> +	 */
>  	if ((cur_state == VFIO_DEVICE_STATE_STOP &&
>  	     new_state == VFIO_DEVICE_STATE_RUNNING) ||
>  	    (cur_state == VFIO_DEVICE_STATE_RUNNING &&
>  	     new_state == VFIO_DEVICE_STATE_STOP)) {
> -		/* TODO */
> -		return ERR_PTR(-EOPNOTSUPP);
> +		return NULL;

[Severity: High]
Does returning NULL here instead of -EOPNOTSUPP allow userspace to silently
leak the active migration file and state?

If a live migration is aborted and transitioned gracefully from STOP to
RUNNING, the old file descriptor could remain active in mig_data because
the driver still holds a reference to the file.

If the process later starts a new migration and transitions to STOP_COPY
again, it looks like vfio_ap_transition_to_state() unconditionally
overwrites mig_data->stop_copy_mig_file.filp:

vfio_ap_transition_to_state() {
    ...
    if (cur_state == VFIO_DEVICE_STATE_STOP &&
        new_state == VFIO_DEVICE_STATE_STOP_COPY) {
        ...
        mig_data->stop_copy_mig_file.filp = filp;
        return filp;
    }
    ...
}

Will this cause the driver's reference to the old file to be permanently lost?

If the old fd is read, vfio_ap_stop_copy_read() might observe that
mig_file->ap_config is already populated and skip updating it, serving
stale configuration to the target.

Additionally, when userspace closes the old fd, its release handler might
fail to match the overwritten filp pointer, which would skip
vfio_device_put_registration() and permanently pin the device.

[Severity: Critical]
With these new state transitions, is there also a risk of use-after-free or
write-after-free regressions during concurrent migration data transfers?

If a userspace process calls read() or write() on the migration file
descriptor, mdevs_lock is temporarily dropped during the data copy:

vfio_ap_stop_copy_read() {
    ...
    mutex_unlock(&matrix_dev->mdevs_lock);

    if (copy_to_user(buf, (char *)mig_file->ap_config + read_pos, len))
    ...
}

Similarly in vfio_ap_resuming_write():

vfio_ap_resuming_write() {
    ...
    mutex_unlock(&matrix_dev->mdevs_lock);

    if (copy_from_user((char *)ap_config + write_pos, buf, len)) {
    ...
}

Can a concurrent thread issue a VFIO_DEVICE_RESET ioctl, close the
device fd, or trigger a state transition that acquires mdevs_lock and
frees ap_config and mig_data?

If so, when the read/write thread resumes execution, it appears it
would access the freed ap_config memory, leading to arbitrary kernel
memory corruption or information leaks.

>  	}
>  
>  	/* vfio_mig_get_next_state() does not use arcs other than the above */

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260727173239.2420754-1-akrowiak@linux.ibm.com?part=12

Re: [PATCH v6 14/15] s390/vfio-ap: Add 'migratable' feature to sysfs 'features' attribute

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The 'migratable' feature is unconditionally advertised in sysfs, even when migration is unsupported and explicitly disabled.
--

--- Patch [14]: [PATCH v6 14/15] s390/vfio-ap: Add 'migratable' feature to sysfs 'features' attribute ---
commit 4ed92108ce1d93cfce3f8740cc391bfad091179c
Author: Anthony Krowiak <akrowiak@linux.ibm.com>

s390/vfio-ap: Add 'migratable' feature to sysfs 'features' attribute

This commit adds the 'migratable' feature to the sysfs features attribute 
to indicate that migration of vfio devices is supported.

> diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
> index 8e69ed286bb9c..4e973736522bc 100644
> --- a/drivers/s390/crypto/vfio_ap_drv.c
> +++ b/drivers/s390/crypto/vfio_ap_drv.c
> @@ -26,9 +26,11 @@ MODULE_LICENSE("GPL v2");
>  struct ap_matrix_dev *matrix_dev;
>  debug_info_t *vfio_ap_dbf_info;
>  
> +#define FEATURES "guest_matrix hotplug ap_config migratable"
> +
>  static ssize_t features_show(struct device *dev, struct device_attribute *attr, char *buf)
>  {
> -	return sysfs_emit(buf, "guest_matrix hotplug ap_config\n");
> +	return sysfs_emit(buf, "%s\n", FEATURES);

[Severity: Medium]
Will this unconditionally advertise the migratable feature even when the
environment does not support it?

If the system is running as a Secure Execution (SE) guest, migration is
typically disabled. By hardcoding "migratable" into the FEATURES string,
management tools like libvirt querying the features sysfs attribute might
incorrectly assume migration is supported. 

This could lead orchestrators to make incorrect VM placement decisions,
followed by unexpected migration failures when QEMU rejects the migration
because the VFIO mdev lacks the capability.

Should features_show() check environmental constraints, such as
ap_is_se_guest(), before including the migratable flag in the output?

>  }
>  static DEVICE_ATTR_RO(features);

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260727173239.2420754-1-akrowiak@linux.ibm.com?part=14