vfio-ccw: make it safe to access channel programs

When we get a solicited interrupt, the start function may have
been cleared by a csch, but we still have a channel program
structure allocated. Make it safe to call the cp accessors in
any case, so we can call them unconditionally.

While at it, also make sure that functions called from other parts
of the code return gracefully if the channel program structure
has not been initialized (even though that is a bug in the caller).

Reviewed-by: Eric Farman <[e-mail]>
Reviewed-by: Farhan Ali <[e-mail]>
Signed-off-by: Cornelia Huck <[e-mail]>

drivers/s390/cio/vfio_ccw_cp.c

···
 	struct ccwchain *chain, *temp;
 	int i;
 
+	cp->initialized = false;
 	list_for_each_entry_safe(chain, temp, &cp->ccwchain_list, next) {
 		for (i = 0; i < chain->ch_len; i++) {
 			pfn_array_table_unpin_free(chain->ch_pat + i,
···
 	 */
 	cp->orb.cmd.c64 = 1;
 
+	if (!ret)
+		cp->initialized = true;
+
 	return ret;
 }
 
···
  */
 void cp_free(struct channel_program *cp)
 {
-	cp_unpin_free(cp);
+	if (cp->initialized)
+		cp_unpin_free(cp);
 }
 
 /**
···
 	struct ccwchain *chain;
 	int len, idx, ret;
 
+	/* this is an error in the caller */
+	if (!cp->initialized)
+		return -EINVAL;
+
 	list_for_each_entry(chain, &cp->ccwchain_list, next) {
 		len = chain->ch_len;
 		for (idx = 0; idx < len; idx++) {
···
 	union orb *orb;
 	struct ccwchain *chain;
 	struct ccw1 *cpa;
+
+	/* this is an error in the caller */
+	if (!cp->initialized)
+		return NULL;
 
 	orb = &cp->orb;
 
···
 	u32 cpa = scsw->cmd.cpa;
 	u32 ccw_head;
 
+	if (!cp->initialized)
+		return;
+
 	/*
 	 * LATER:
 	 * For now, only update the cmd.cpa part. We may need to deal with
···
 {
 	struct ccwchain *chain;
 	int i;
+
+	if (!cp->initialized)
+		return false;
 
 	list_for_each_entry(chain, &cp->ccwchain_list, next) {
 		for (i = 0; i < chain->ch_len; i++)

drivers/s390/cio/vfio_ccw_cp.h

···
  * @ccwchain_list: list head of ccwchains
  * @orb: orb for the currently processed ssch request
  * @mdev: the mediated device to perform page pinning/unpinning
+ * @initialized: whether this instance is actually initialized
  *
  * @ccwchain_list is the head of a ccwchain list, that contents the
  * translated result of the guest channel program that pointed out by
···
 	struct list_head ccwchain_list;
 	union orb orb;
 	struct device *mdev;
+	bool initialized;
 };
 
 extern int cp_init(struct channel_program *cp, struct device *mdev,

drivers/s390/cio/vfio_ccw_fsm.c

···
 	private->state = VFIO_CCW_STATE_BUSY;
 
 	orb = cp_get_orb(&private->cp, (u32)(addr_t)sch, sch->lpm);
+	if (!orb) {
+		ret = -EIO;
+		goto out;
+	}
 
 	/* Issue "Start Subchannel" */
 	ccode = ssch(sch->schid, orb);
···
 	default:
 		ret = ccode;
 	}
+out:
 	spin_unlock_irqrestore(sch->lock, flags);
 	return ret;
 }