[PATCH v4 0/5] s390/vfio-ap: ap_config sysfs attribute for mdevctl automation

[PATCH v4 0/5] s390/vfio-ap: ap_config sysfs attribute for mdevctl automation

[Jason J. Herne]

Mdevctl requires a way to atomically query and atomically update a vfio-ap
mdev's current state. This patch set creates the ap_config sysfs attribute.
This new attribute allows reading and writing an mdev's entire state in one go.
If a newly written state is invalid for any reason the entire state is rejected
and the target mdev remains unchanged.

Changelog
==========
v4
  - Added volatile cast to fixup false positive gcc warning: 
    Wstringop-overread-warning
  - Added new Reviewed-By tags
v3
  - Optimization: hot unplug functions skip apcb update if nothing was actually
    unplugged.
  - Hot unplug functions modified to zero bitmaps before use.
  - Rename ap_matrix_length_check to ap_matrix_overflow_check
  - Fixed omissions and errors in several commit messages and the docs.
  - Added Tested-by tags.
v2
  - Rebased patched on top of latest master
  - Reworked code to fit changes introduced by f848cba767e59
      s390/vfio-ap: reset queues filtered from the guest's AP config
  - Moved docs changes to separate patch


Jason J. Herne (5):
  s390/ap: Externalize AP bus specific bitmap reading function
  s390/vfio-ap: Add sysfs attr, ap_config, to export mdev state
  s390/vfio-ap: Ignore duplicate link requests in
    vfio_ap_mdev_link_queue
  s390/vfio-ap: Add write support to sysfs attr ap_config
  docs: Update s390 vfio-ap doc for ap_config sysfs attribute

 Documentation/arch/s390/vfio-ap.rst   |  30 ++++
 drivers/s390/crypto/ap_bus.c          |  13 +-
 drivers/s390/crypto/ap_bus.h          |  22 +++
 drivers/s390/crypto/vfio_ap_ops.c     | 223 ++++++++++++++++++++++++--
 drivers/s390/crypto/vfio_ap_private.h |   6 +-
 5 files changed, 265 insertions(+), 29 deletions(-)

-- 
2.41.0

[PATCH v4 1/5] s390/ap: Externalize AP bus specific bitmap reading function

[Jason J. Herne]

Rename hex2bitmap() to ap_hex2bitmap() and export it for external
use. This function will be used by the implementation of the vfio-ap
ap_config sysfs attribute.

Signed-off-by: Jason J. Herne <jjherne@linux.ibm.com>
Reviewed-by: Tony Krowiak <akrowiak@linux.ibm.com>
Reviewed-by: Harald Freudenberger <freude@linux.ibm.com>
---
 drivers/s390/crypto/ap_bus.c | 13 +++----------
 drivers/s390/crypto/ap_bus.h | 22 ++++++++++++++++++++++
 2 files changed, 25 insertions(+), 10 deletions(-)

diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c
index cce0bafd4c92..1be07197eda3 100644
--- a/drivers/s390/crypto/ap_bus.c
+++ b/drivers/s390/crypto/ap_bus.c
@@ -1068,15 +1068,7 @@ void ap_bus_cfg_chg(void)
 	ap_bus_force_rescan();
 }
 
-/*
- * hex2bitmap() - parse hex mask string and set bitmap.
- * Valid strings are "0x012345678" with at least one valid hex number.
- * Rest of the bitmap to the right is padded with 0. No spaces allowed
- * within the string, the leading 0x may be omitted.
- * Returns the bitmask with exactly the bits set as given by the hex
- * string (both in big endian order).
- */
-static int hex2bitmap(const char *str, unsigned long *bitmap, int bits)
+int ap_hex2bitmap(const char *str, unsigned long *bitmap, int bits)
 {
 	int i, n, b;
 
@@ -1103,6 +1095,7 @@ static int hex2bitmap(const char *str, unsigned long *bitmap, int bits)
 		return -EINVAL;
 	return 0;
 }
+EXPORT_SYMBOL(ap_hex2bitmap);
 
 /*
  * modify_bitmap() - parse bitmask argument and modify an existing
@@ -1168,7 +1161,7 @@ static int ap_parse_bitmap_str(const char *str, unsigned long *bitmap, int bits,
 		rc = modify_bitmap(str, newmap, bits);
 	} else {
 		memset(newmap, 0, size);
-		rc = hex2bitmap(str, newmap, bits);
+		rc = ap_hex2bitmap(str, newmap, bits);
 	}
 	return rc;
 }
diff --git a/drivers/s390/crypto/ap_bus.h b/drivers/s390/crypto/ap_bus.h
index 59c7ed49aa02..1db9597509da 100644
--- a/drivers/s390/crypto/ap_bus.h
+++ b/drivers/s390/crypto/ap_bus.h
@@ -343,6 +343,28 @@ int ap_parse_mask_str(const char *str,
 		      unsigned long *bitmap, int bits,
 		      struct mutex *lock);
 
+/*
+ * ap_hex2bitmap() - Convert a string containing a hexadecimal number (str)
+ * into a bitmap (bitmap) with bits set that correspond to the bits represented
+ * by the hex string. Input and output data is in big endian order.
+ *
+ * str - Input hex string of format "0x1234abcd". The leading "0x" is optional.
+ * At least one digit is required. Must be large enough to hold the number of
+ * bits represented by the bits parameter.
+ *
+ * bitmap - Pointer to a bitmap. Upon successful completion of this function,
+ * this bitmap will have bits set to match the value of str. If bitmap is longer
+ * than str, then the rightmost bits of bitmap are padded with zeros. Must be
+ * large enough to hold the number of bits represented by the bits parameter.
+ *
+ * bits - Length, in bits, of the bitmap represented by str. Must be a multiple
+ * of 8.
+ *
+ * Returns: 0           on success
+ *          -EINVAL     If str format is invalid or bits is not a multiple of 8.
+ */
+int ap_hex2bitmap(const char *str, unsigned long *bitmap, int bits);
+
 /*
  * Interface to wait for the AP bus to have done one initial ap bus
  * scan and all detected APQNs have been bound to device drivers.
-- 
2.41.0

[PATCH v4 2/5] s390/vfio-ap: Add sysfs attr, ap_config, to export mdev state

[Jason J. Herne]

Add ap_config sysfs attribute. This will provide the means for
setting or displaying the adapters, domains and control domains assigned
to the vfio-ap mediated device in a single operation. This sysfs
attribute is comprised of three masks: One for adapters, one for domains,
and one for control domains.

This attribute is intended to be used by mdevctl to query a vfio-ap
mediated device's state.

Signed-off-by: Jason J. Herne <jjherne@linux.ibm.com>
Reviewed-by: Tony Krowiak <akrowiak@linux.ibm.com>
Tested-by: Matthew Rosato <mjrosato@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_ops.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index fc169bc61593..e01f53a3c5b7 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -1570,6 +1570,32 @@ static ssize_t guest_matrix_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(guest_matrix);
 
+static ssize_t write_ap_bitmap(unsigned long *bitmap, char *buf, int offset, char sep)
+{
+	return sysfs_emit_at(buf, offset, "0x%016lx%016lx%016lx%016lx%c",
+			 bitmap[0], bitmap[1], bitmap[2], bitmap[3], sep);
+}
+
+static ssize_t ap_config_show(struct device *dev, struct device_attribute *attr,
+			      char *buf)
+{
+	struct ap_matrix_mdev *matrix_mdev = dev_get_drvdata(dev);
+	int idx = 0;
+
+	idx += write_ap_bitmap(matrix_mdev->matrix.apm, buf, idx, ',');
+	idx += write_ap_bitmap(matrix_mdev->matrix.aqm, buf, idx, ',');
+	idx += write_ap_bitmap(matrix_mdev->matrix.adm, buf, idx, '\n');
+
+	return idx;
+}
+
+static ssize_t ap_config_store(struct device *dev, struct device_attribute *attr,
+			       const char *buf, size_t count)
+{
+	return count;
+}
+static DEVICE_ATTR_RW(ap_config);
+
 static struct attribute *vfio_ap_mdev_attrs[] = {
 	&dev_attr_assign_adapter.attr,
 	&dev_attr_unassign_adapter.attr,
@@ -1577,6 +1603,7 @@ static struct attribute *vfio_ap_mdev_attrs[] = {
 	&dev_attr_unassign_domain.attr,
 	&dev_attr_assign_control_domain.attr,
 	&dev_attr_unassign_control_domain.attr,
+	&dev_attr_ap_config.attr,
 	&dev_attr_control_domains.attr,
 	&dev_attr_matrix.attr,
 	&dev_attr_guest_matrix.attr,
-- 
2.41.0

[PATCH v4 3/5] s390/vfio-ap: Ignore duplicate link requests in vfio_ap_mdev_link_queue

[Jason J. Herne]

vfio_ap_mdev_link_queue is changed to detect if a matrix_mdev has
already linked the given queue. If so, it bails out.

Signed-off-by: Jason J. Herne <jjherne@linux.ibm.com>
Reviewed-by: Tony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_ops.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index e01f53a3c5b7..1499c2181122 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -794,10 +794,11 @@ static int vfio_ap_mdev_probe(struct mdev_device *mdev)
 static void vfio_ap_mdev_link_queue(struct ap_matrix_mdev *matrix_mdev,
 				    struct vfio_ap_queue *q)
 {
-	if (q) {
-		q->matrix_mdev = matrix_mdev;
-		hash_add(matrix_mdev->qtable.queues, &q->mdev_qnode, q->apqn);
-	}
+	if (!q || vfio_ap_mdev_get_queue(matrix_mdev, q->apqn))
+		return;
+
+	q->matrix_mdev = matrix_mdev;
+	hash_add(matrix_mdev->qtable.queues, &q->mdev_qnode, q->apqn);
 }
 
 static void vfio_ap_mdev_link_apqn(struct ap_matrix_mdev *matrix_mdev, int apqn)
-- 
2.41.0

[PATCH v4 4/5] s390/vfio-ap: Add write support to sysfs attr ap_config

[Jason J. Herne]

Allow writing a complete set of masks to ap_config. Doing so will
cause the vfio-ap driver to replace the vfio-ap mediated device's
matrix masks with the given set of masks. If the given state cannot
be set, then no changes are made to the vfio-ap mediated device.

The format of the data written to ap_config is as follows:
{amask},{dmask},{cmask}\n

\n is a newline character.

amask, dmask, and cmask are masks identifying which adapters, domains,
and control domains should be assigned to the mediated device.

The format of a mask is as follows:
0xNN..NN

Where NN..NN is 64 hexadecimal characters representing a 256-bit value.
The leftmost (highest order) bit represents adapter/domain 0.

For an example set of masks that represent your mdev's current
configuration, simply cat ap_config.

This attribute is intended to be used by an mdevctl callout script
supporting the mdev type vfio_ap-passthrough to atomically update a
vfio-ap mediated device's state.

Signed-off-by: Jason J. Herne <jjherne@linux.ibm.com>
Reviewed-by: Tony Krowiak <akrowiak@linux.ibm.com>
Tested-by: Matthew Rosato <mjrosato@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_ops.c     | 189 ++++++++++++++++++++++++--
 drivers/s390/crypto/vfio_ap_private.h |   6 +-
 2 files changed, 179 insertions(+), 16 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 1499c2181122..ad01979c41d6 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -1119,20 +1119,29 @@ static void vfio_ap_mdev_unlink_adapter(struct ap_matrix_mdev *matrix_mdev,
 	}
 }
 
-static void vfio_ap_mdev_hot_unplug_adapter(struct ap_matrix_mdev *matrix_mdev,
-					    unsigned long apid)
+static void vfio_ap_mdev_hot_unplug_adapters(struct ap_matrix_mdev *matrix_mdev,
+					    unsigned long *apids)
 {
 	struct vfio_ap_queue *q, *tmpq;
 	struct list_head qlist;
+	unsigned long apid;
+	bool apcb_update = false;
 
 	INIT_LIST_HEAD(&qlist);
-	vfio_ap_mdev_unlink_adapter(matrix_mdev, apid, &qlist);
 
-	if (test_bit_inv(apid, matrix_mdev->shadow_apcb.apm)) {
-		clear_bit_inv(apid, matrix_mdev->shadow_apcb.apm);
-		vfio_ap_mdev_update_guest_apcb(matrix_mdev);
+	for_each_set_bit_inv(apid, apids, AP_DEVICES) {
+		vfio_ap_mdev_unlink_adapter(matrix_mdev, apid, &qlist);
+
+		if (test_bit_inv(apid, matrix_mdev->shadow_apcb.apm)) {
+			clear_bit_inv(apid, matrix_mdev->shadow_apcb.apm);
+			apcb_update = true;
+		}
 	}
 
+	/* Only update apcb if needed to avoid impacting guest */
+	if (apcb_update)
+		vfio_ap_mdev_update_guest_apcb(matrix_mdev);
+
 	vfio_ap_mdev_reset_qlist(&qlist);
 
 	list_for_each_entry_safe(q, tmpq, &qlist, reset_qnode) {
@@ -1141,6 +1150,16 @@ static void vfio_ap_mdev_hot_unplug_adapter(struct ap_matrix_mdev *matrix_mdev,
 	}
 }
 
+static void vfio_ap_mdev_hot_unplug_adapter(struct ap_matrix_mdev *matrix_mdev,
+					    unsigned long apid)
+{
+	DECLARE_BITMAP(apids, AP_DEVICES);
+
+	bitmap_zero(apids, AP_DEVICES);
+	set_bit_inv(apid, apids);
+	vfio_ap_mdev_hot_unplug_adapters(matrix_mdev, apids);
+}
+
 /**
  * unassign_adapter_store - parses the APID from @buf and clears the
  * corresponding bit in the mediated matrix device's APM
@@ -1301,20 +1320,29 @@ static void vfio_ap_mdev_unlink_domain(struct ap_matrix_mdev *matrix_mdev,
 	}
 }
 
-static void vfio_ap_mdev_hot_unplug_domain(struct ap_matrix_mdev *matrix_mdev,
-					   unsigned long apqi)
+static void vfio_ap_mdev_hot_unplug_domains(struct ap_matrix_mdev *matrix_mdev,
+					   unsigned long *apqis)
 {
 	struct vfio_ap_queue *q, *tmpq;
 	struct list_head qlist;
+	unsigned long apqi;
+	bool apcb_update = false;
 
 	INIT_LIST_HEAD(&qlist);
-	vfio_ap_mdev_unlink_domain(matrix_mdev, apqi, &qlist);
 
-	if (test_bit_inv(apqi, matrix_mdev->shadow_apcb.aqm)) {
-		clear_bit_inv(apqi, matrix_mdev->shadow_apcb.aqm);
-		vfio_ap_mdev_update_guest_apcb(matrix_mdev);
+	for_each_set_bit_inv(apqi, apqis, AP_DOMAINS) {
+		vfio_ap_mdev_unlink_domain(matrix_mdev, apqi, &qlist);
+
+		if (test_bit_inv(apqi, matrix_mdev->shadow_apcb.aqm)) {
+			clear_bit_inv(apqi, matrix_mdev->shadow_apcb.aqm);
+			apcb_update = true;
+		}
 	}
 
+	/* Only update apcb if needed to avoid impacting guest */
+	if (apcb_update)
+		vfio_ap_mdev_update_guest_apcb(matrix_mdev);
+
 	vfio_ap_mdev_reset_qlist(&qlist);
 
 	list_for_each_entry_safe(q, tmpq, &qlist, reset_qnode) {
@@ -1323,6 +1351,16 @@ static void vfio_ap_mdev_hot_unplug_domain(struct ap_matrix_mdev *matrix_mdev,
 	}
 }
 
+static void vfio_ap_mdev_hot_unplug_domain(struct ap_matrix_mdev *matrix_mdev,
+					   unsigned long apqi)
+{
+	DECLARE_BITMAP(apqis, AP_DOMAINS);
+
+	bitmap_zero(apqis, AP_DEVICES);
+	set_bit_inv(apqi, apqis);
+	vfio_ap_mdev_hot_unplug_domains(matrix_mdev, apqis);
+}
+
 /**
  * unassign_domain_store - parses the APQI from @buf and clears the
  * corresponding bit in the mediated matrix device's AQM
@@ -1590,10 +1628,135 @@ static ssize_t ap_config_show(struct device *dev, struct device_attribute *attr,
 	return idx;
 }
 
+/* Number of characters needed for a complete hex mask representing the bits in ..  */
+#define AP_DEVICES_STRLEN	(AP_DEVICES/4 + 3)
+#define AP_DOMAINS_STRLEN	(AP_DOMAINS/4 + 3)
+#define AP_CONFIG_STRLEN	(AP_DEVICES_STRLEN + 2 * AP_DOMAINS_STRLEN)
+
+static int parse_bitmap(char **strbufptr, unsigned long *bitmap, int nbits)
+{
+	char *curmask;
+
+	curmask = strsep(strbufptr, ",\n");
+	if (!curmask)
+		return -EINVAL;
+
+	bitmap_clear(bitmap, 0, nbits);
+	return ap_hex2bitmap(curmask, bitmap, nbits);
+}
+
+static int ap_matrix_overflow_check(struct ap_matrix_mdev *matrix_mdev)
+{
+	unsigned long bit;
+
+	for_each_set_bit_inv(bit, matrix_mdev->matrix.apm, AP_DEVICES) {
+		if (bit > matrix_mdev->matrix.apm_max)
+			return -ENODEV;
+	}
+
+	for_each_set_bit_inv(bit, matrix_mdev->matrix.aqm, AP_DOMAINS) {
+		if (bit > matrix_mdev->matrix.aqm_max)
+			return -ENODEV;
+	}
+
+	for_each_set_bit_inv(bit, matrix_mdev->matrix.adm, AP_DOMAINS) {
+		if (bit > matrix_mdev->matrix.adm_max)
+			return -ENODEV;
+	}
+
+	return 0;
+}
+
+static void ap_matrix_copy(struct ap_matrix *dst, struct ap_matrix *src)
+{
+	bitmap_copy(dst->apm, src->apm, AP_DEVICES);
+	bitmap_copy(dst->aqm, src->aqm, AP_DOMAINS);
+	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)
 {
-	return count;
+	struct ap_matrix_mdev *matrix_mdev = dev_get_drvdata(dev);
+	struct ap_matrix m_new, m_old, m_added, m_removed;
+	DECLARE_BITMAP(apm_filtered, AP_DEVICES);
+	unsigned long newbit;
+	char *newbuf, *rest;
+	int rc = count;
+	bool do_update;
+
+	newbuf = rest = kstrndup(buf, AP_CONFIG_STRLEN, GFP_KERNEL);
+	if (!newbuf)
+		return -ENOMEM;
+
+	mutex_lock(&ap_perms_mutex);
+	get_update_locks_for_mdev(matrix_mdev);
+
+	/* Save old state */
+	/* The volatile cast here is to work around a gcc false positive
+	 * Wstringop-overread-warning.
+	 */
+	ap_matrix_copy(&m_old, (*(struct ap_matrix * volatile *)(&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;
+	}
+
+	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);
+
+	/* Need new bitmaps in matrix_mdev for validation */
+	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);
+	if (rc) {
+		ap_matrix_copy(&matrix_mdev->matrix, &m_old);
+		goto out;
+	}
+	rc = count;
+
+	/* Need old bitmaps in matrix_mdev for unplug/unlink */
+	ap_matrix_copy(&matrix_mdev->matrix, &m_old);
+
+	/* Unlink removed adapters/domains */
+	vfio_ap_mdev_hot_unplug_adapters(matrix_mdev, m_removed.apm);
+	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);
+
+	for_each_set_bit_inv(newbit, m_added.aqm, AP_DOMAINS)
+		vfio_ap_mdev_link_domain(matrix_mdev, newbit);
+
+	/* filter resources not bound to vfio-ap */
+	do_update = vfio_ap_mdev_filter_matrix(matrix_mdev, apm_filtered);
+	do_update |= vfio_ap_mdev_filter_cdoms(matrix_mdev);
+
+	/* Apply changes to shadow apbc if things changed */
+	if (do_update) {
+		vfio_ap_mdev_update_guest_apcb(matrix_mdev);
+		reset_queues_for_apids(matrix_mdev, apm_filtered);
+	}
+out:
+	release_update_locks_for_mdev(matrix_mdev);
+	mutex_unlock(&ap_perms_mutex);
+	kfree(newbuf);
+	return rc;
 }
 static DEVICE_ATTR_RW(ap_config);
 
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index 98d37aa27044..437a161c8659 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -75,11 +75,11 @@ extern struct ap_matrix_dev *matrix_dev;
  */
 struct ap_matrix {
 	unsigned long apm_max;
-	DECLARE_BITMAP(apm, 256);
+	DECLARE_BITMAP(apm, AP_DEVICES);
 	unsigned long aqm_max;
-	DECLARE_BITMAP(aqm, 256);
+	DECLARE_BITMAP(aqm, AP_DOMAINS);
 	unsigned long adm_max;
-	DECLARE_BITMAP(adm, 256);
+	DECLARE_BITMAP(adm, AP_DOMAINS);
 };
 
 /**
-- 
2.41.0

Re: [PATCH v4 4/5] s390/vfio-ap: Add write support to sysfs attr ap_config

[Alexander Gordeev]

On Tue, Mar 26, 2024 at 12:47:05PM -0400, Jason J. Herne wrote:

Hi Jason,

This series still has some issues.

> +	newbuf = rest = kstrndup(buf, AP_CONFIG_STRLEN, GFP_KERNEL);

This line triggers a checkpatch warning. Would it make sense
to turn it into below instead?

	newbuf = kstrndup(buf, AP_CONFIG_STRLEN, GFP_KERNEL);
> +	if (!newbuf)
> +		return -ENOMEM;
	rest = newbuf;

Also, please address other checkpatch suggestions.

> +	/* Save old state */
> +	/* The volatile cast here is to work around a gcc false positive
> +	 * Wstringop-overread-warning.
> +	 */
> +	ap_matrix_copy(&m_old, (*(struct ap_matrix * volatile *)(&matrix_mdev->matrix)));

Could you please come up with a different workaround? This issue has already
been resolved in the past in different ways. See commit 34186b48d29b ("ARM:
sharpsl_param: work around -Wstringop-overread warning") for example.

Thanks!

Re: [PATCH v4 4/5] s390/vfio-ap: Add write support to sysfs attr ap_config

[Jason J. Herne]

On 4/8/24 10:22 AM, Alexander Gordeev wrote:
> On Tue, Mar 26, 2024 at 12:47:05PM -0400, Jason J. Herne wrote:
> 
> Hi Jason,
> 
> This series still has some issues.
> 
>> +	newbuf = rest = kstrndup(buf, AP_CONFIG_STRLEN, GFP_KERNEL);
> 
> This line triggers a checkpatch warning. Would it make sense
> to turn it into below instead?
> 
> 	newbuf = kstrndup(buf, AP_CONFIG_STRLEN, GFP_KERNEL);
>> +	if (!newbuf)
>> +		return -ENOMEM;
> 	rest = newbuf;

Yes, I can make that change. My checkpatch.pl script does not point this
issue out with --strict. Should I be running checkpatch with --strict?

> Also, please address other checkpatch suggestions.
> 

Yep, I'll run with --strict and address everything.

>> +	/* Save old state */
>> +	/* The volatile cast here is to work around a gcc false positive
>> +	 * Wstringop-overread-warning.
>> +	 */
>> +	ap_matrix_copy(&m_old, (*(struct ap_matrix * volatile *)(&matrix_mdev->matrix)));
> 
> Could you please come up with a different workaround? This issue has already
> been resolved in the past in different ways. See commit 34186b48d29b ("ARM:
> sharpsl_param: work around -Wstringop-overread warning") for example.

Sure, I like this solution way better than using volatile. Thanks for
providing the pointer to this.

Re: [PATCH v4 4/5] s390/vfio-ap: Add write support to sysfs attr ap_config

[Alexander Gordeev]

On Fri, Apr 12, 2024 at 08:29:44AM -0400, Jason J. Herne wrote:
Hi Jason,
> Yes, I can make that change. My checkpatch.pl script does not point this
> issue out with --strict. Should I be running checkpatch with --strict?

Yes.
AFAIR --strict produced that.

> > Also, please address other checkpatch suggestions.
> Yep, I'll run with --strict and address everything.

Thanks!

[PATCH v4 5/5] docs: Update s390 vfio-ap doc for ap_config sysfs attribute

[Jason J. Herne]

A new sysfs attribute, ap_config, for the vfio_ap driver is
documented.

Signed-off-by: Jason J. Herne <jjherne@linux.ibm.com>
Reviewed-by: Tony Krowiak <akrowiak@linux.ibm.com>
---
 Documentation/arch/s390/vfio-ap.rst | 30 +++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/Documentation/arch/s390/vfio-ap.rst b/Documentation/arch/s390/vfio-ap.rst
index 929ee1c1c940..6056a50ee841 100644
--- a/Documentation/arch/s390/vfio-ap.rst
+++ b/Documentation/arch/s390/vfio-ap.rst
@@ -380,6 +380,36 @@ matrix device.
     control_domains:
       A read-only file for displaying the control domain numbers assigned to the
       vfio_ap mediated device.
+    ap_config:
+        A read/write file that, when written to, allows all three of the
+        vfio_ap mediated device's ap matrix masks to be replaced in one shot.
+        Three masks are given, one for adapters, one for domains, and one for
+        control domains. If the given state cannot be set then no changes are
+        made to the vfio-ap mediated device.
+
+        The format of the data written to ap_config is as follows:
+        {amask},{dmask},{cmask}\n
+
+        \n is a newline character.
+
+        amask, dmask, and cmask are masks identifying which adapters, domains,
+        and control domains should be assigned to the mediated device.
+
+        The format of a mask is as follows:
+        0xNN..NN
+
+        Where NN..NN is 64 hexadecimal characters representing a 256-bit value.
+        The leftmost (highest order) bit represents adapter/domain 0.
+
+        For an example set of masks that represent your mdev's current
+        configuration, simply cat ap_config.
+
+        Setting an adapter or domain number greater than the maximum allowed for
+        the system will result in an error.
+
+        This attribute is intended to be used by automation. End users would be
+        better served using the respective assign/unassign attributes for
+        adapters, domains, and control domains.
 
 * functions:
 
-- 
2.41.0