s390/AP: support new dynamic AP bus size limit

This patch provides support for new dynamic AP bus message limit
with the existing zcrypt device driver and AP bus core code.

There is support for a new field 'ml' from TAPQ query. The field
gives if != 0 the AP bus limit for this card in 4k chunk units.
The actual message size limit per card is shown as a new read-only
sysfs attribute. The sysfs attribute

  /sys/devices/ap/cardxx/max_msg_size

shows the upper limit in bytes used by the AP bus and zcrypt device
driver for requests and replies send to and received from this card.
Currently up to CEX7 support only max 12kB msg size and thus the field
shows 12288 meaning the upper limit of a valid msg for this card is
12kB. Please note that the usable payload is somewhat lower and
depends on the msg type and thus the header struct which is to be
prepended by the zcrypt dd.

The dispatcher responsible for choosing the right card and queue is
aware of the individual card AP bus message limit. So a request is
only assigned to a queue of a card which is able to handle the size of
the request (e.g. a 14kB request will never go to a max 12kB card).
If no such card is found the ioctl will fail with ENODEV.

The reply buffer held by the device driver is determined by the ml
field of the TAPQ for this card. If a response from the card exceeds
this limit however, the response is not truncated but the ioctl for
this request will fail with errno EMSGSIZE to indicate that the device
driver has dropped the response because it would overflow the buffer
limit.

If the request size does not indicate to the dispatcher that an
adapter with extended limit is to be used, a random card will be
chosen when no specific card is addressed (ANY addressing). This may
result in an ioctl failure when the reply size needs an adapter with
extended limit but the randomly chosen one is not capable of handling
the broader reply size. The user space application needs to use
dedicated addressing to forward such a request only to suitable cards
to get requests like this processed properly.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Ingo Tuchscherer <ingo.tuchscherer@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

1 files changed, 37 insertions, 13 deletions

diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c
index d2560186d771..8d3a1d84a757 100644
--- a/drivers/s390/crypto/ap_bus.c
+++ b/drivers/s390/crypto/ap_bus.c
@@ -61,6 +61,9 @@ static char *aqm_str;
 module_param_named(aqmask, aqm_str, charp, 0440);
 MODULE_PARM_DESC(aqmask, "AP bus domain mask.");
 
+atomic_t ap_max_msg_size = ATOMIC_INIT(AP_DEFAULT_MAX_MSG_SIZE);
+EXPORT_SYMBOL(ap_max_msg_size);
+
 static struct device *ap_root_device;
 
 /* Hashtable of all queue devices on the AP bus */
@@ -316,11 +319,24 @@ EXPORT_SYMBOL(ap_test_config_ctrl_domain);
  * Returns true if TAPQ succeeded and the info is filled or
  * false otherwise.
  */
-static bool ap_queue_info(ap_qid_t qid, int *q_type,
-			  unsigned int *q_fac, int *q_depth, bool *q_decfg)
+static bool ap_queue_info(ap_qid_t qid, int *q_type, unsigned int *q_fac,
+			  int *q_depth, int *q_ml, bool *q_decfg)
 {
 	struct ap_queue_status status;
-	unsigned long info = 0;
+	union {
+		unsigned long value;
+		struct {
+			unsigned int fac   : 32; /* facility bits */
+			unsigned int at	   :  8; /* ap type */
+			unsigned int _res1 :  8;
+			unsigned int _res2 :  4;
+			unsigned int ml	   :  4; /* apxl ml */
+			unsigned int _res3 :  4;
+			unsigned int qd	   :  4; /* queue depth */
+		} tapq_gr2;
+	} tapq_info;
+
+	tapq_info.value = 0;
 
 	/* make sure we don't run into a specifiation exception */
 	if (AP_QID_CARD(qid) > ap_max_adapter_id ||
@@ -328,7 +344,7 @@ static bool ap_queue_info(ap_qid_t qid, int *q_type,
 		return false;
 
 	/* call TAPQ on this APQN */
-	status = ap_test_queue(qid, ap_apft_available(), &info);
+	status = ap_test_queue(qid, ap_apft_available(), &tapq_info.value);
 	switch (status.response_code) {
 	case AP_RESPONSE_NORMAL:
 	case AP_RESPONSE_RESET_IN_PROGRESS:
@@ -340,11 +356,12 @@ static bool ap_queue_info(ap_qid_t qid, int *q_type,
 		 * info should be filled. All bits 0 is not possible as
 		 * there is at least one of the mode bits set.
 		 */
-		if (WARN_ON_ONCE(!info))
+		if (WARN_ON_ONCE(!tapq_info.value))
 			return false;
-		*q_type = (int)((info >> 24) & 0xff);
-		*q_fac = (unsigned int)(info >> 32);
-		*q_depth = (int)(info & 0xff);
+		*q_type = tapq_info.tapq_gr2.at;
+		*q_fac = tapq_info.tapq_gr2.fac;
+		*q_depth = tapq_info.tapq_gr2.qd;
+		*q_ml = tapq_info.tapq_gr2.ml;
 		*q_decfg = status.response_code == AP_RESPONSE_DECONFIGURED;
 		switch (*q_type) {
 			/* For CEX2 and CEX3 the available functions
@@ -1516,7 +1533,7 @@ static inline void ap_scan_domains(struct ap_card *ac)
 	unsigned int func;
 	struct device *dev;
 	struct ap_queue *aq;
-	int rc, dom, depth, type;
+	int rc, dom, depth, type, ml;
 
 	/*
 	 * Go through the configuration for the domains and compare them
@@ -1540,7 +1557,7 @@ static inline void ap_scan_domains(struct ap_card *ac)
 			continue;
 		}
 		/* domain is valid, get info from this APQN */
-		if (!ap_queue_info(qid, &type, &func, &depth, &decfg)) {
+		if (!ap_queue_info(qid, &type, &func, &depth, &ml, &decfg)) {
 			if (aq) {
 				AP_DBF_INFO(
 					"%s(%d,%d) ap_queue_info() not successful, rm queue device\n",
@@ -1639,7 +1656,7 @@ static inline void ap_scan_adapter(int ap)
 	unsigned int func;
 	struct device *dev;
 	struct ap_card *ac;
-	int rc, dom, depth, type, comp_type;
+	int rc, dom, depth, type, comp_type, ml;
 
 	/* Is there currently a card device for this adapter ? */
 	dev = bus_find_device(&ap_bus_type, NULL,
@@ -1668,7 +1685,8 @@ static inline void ap_scan_adapter(int ap)
 	for (dom = 0; dom <= ap_max_domain_id; dom++)
 		if (ap_test_config_usage_domain(dom)) {
 			qid = AP_MKQID(ap, dom);
-			if (ap_queue_info(qid, &type, &func, &depth, &decfg))
+			if (ap_queue_info(qid, &type, &func,
+					  &depth, &ml, &decfg))
 				break;
 		}
 	if (dom > ap_max_domain_id) {
@@ -1737,7 +1755,7 @@ static inline void ap_scan_adapter(int ap)
 				    __func__, ap, type);
 			return;
 		}
-		ac = ap_card_create(ap, depth, type, comp_type, func);
+		ac = ap_card_create(ap, depth, type, comp_type, func, ml);
 		if (!ac) {
 			AP_DBF_WARN("%s(%d) ap_card_create() failed\n",
 				    __func__, ap);
@@ -1748,6 +1766,12 @@ static inline void ap_scan_adapter(int ap)
 		dev->bus = &ap_bus_type;
 		dev->parent = ap_root_device;
 		dev_set_name(dev, "card%02x", ap);
+		/* maybe enlarge ap_max_msg_size to support this card */
+		if (ac->maxmsgsize > atomic_read(&ap_max_msg_size)) {
+			atomic_set(&ap_max_msg_size, ac->maxmsgsize);
+			AP_DBF_INFO("%s(%d) ap_max_msg_size update to %d byte\n",
+				    __func__, ap, atomic_read(&ap_max_msg_size));
+		}
 		/* Register the new card device with AP bus */
 		rc = device_register(dev);
 		if (rc) {