s390/sclp: do not use static sccbs

The sccbs for init/read/sdias/early have to be located below 2 GB, and
they are currently defined as a static buffer.

With a relocatable kernel that could reside at any place in memory, this
will no longer guarantee the location below 2 GB, so use a dynamic
GFP_DMA allocation instead.

The sclp_early_sccb buffer needs special handling, as it can be used
very early, and by both the decompressor and also the decompressed
kernel. Therefore, a fixed 4 KB buffer is introduced at 0x11000, the
former PARMAREA_END. The new PARMAREA_END is now 0x12000, and it is
renamed to HEAD_END, as it is rather the end of head.S and not the end
of the parmarea.

Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Reviewed-by: Philipp Rudo <prudo@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/char/sclp.c

@@ -45,8 +45,8 @@ static struct list_head sclp_req_queue;
 /* Data for read and and init requests. */
 static struct sclp_req sclp_read_req;
 static struct sclp_req sclp_init_req;
-static char sclp_read_sccb[PAGE_SIZE] __attribute__((__aligned__(PAGE_SIZE)));
-static char sclp_init_sccb[PAGE_SIZE] __attribute__((__aligned__(PAGE_SIZE)));
+static void *sclp_read_sccb;
+static struct init_sccb *sclp_init_sccb;
 
 /* Suspend request */
 static DECLARE_COMPLETION(sclp_request_queue_flushed);
@@ -753,9 +753,8 @@ EXPORT_SYMBOL(sclp_remove_processed);
 static inline void
 __sclp_make_init_req(sccb_mask_t receive_mask, sccb_mask_t send_mask)
 {
-	struct init_sccb *sccb;
+	struct init_sccb *sccb = sclp_init_sccb;
 
-	sccb = (struct init_sccb *) sclp_init_sccb;
 	clear_page(sccb);
 	memset(&sclp_init_req, 0, sizeof(struct sclp_req));
 	sclp_init_req.command = SCLP_CMDW_WRITE_EVENT_MASK;
@@ -782,7 +781,7 @@ static int
 sclp_init_mask(int calculate)
 {
 	unsigned long flags;
-	struct init_sccb *sccb = (struct init_sccb *) sclp_init_sccb;
+	struct init_sccb *sccb = sclp_init_sccb;
 	sccb_mask_t receive_mask;
 	sccb_mask_t send_mask;
 	int retry;
@@ -1175,6 +1174,9 @@ sclp_init(void)
 	if (sclp_init_state != sclp_init_state_uninitialized)
 		goto fail_unlock;
 	sclp_init_state = sclp_init_state_initializing;
+	sclp_read_sccb = (void *) __get_free_page(GFP_ATOMIC | GFP_DMA);
+	sclp_init_sccb = (void *) __get_free_page(GFP_ATOMIC | GFP_DMA);
+	BUG_ON(!sclp_read_sccb || !sclp_init_sccb);
 	/* Set up variables */
 	INIT_LIST_HEAD(&sclp_req_queue);
 	INIT_LIST_HEAD(&sclp_reg_list);
@@ -1207,6 +1209,8 @@ fail_unregister_reboot_notifier:
 	unregister_reboot_notifier(&sclp_reboot_notifier);
 fail_init_state_uninitialized:
 	sclp_init_state = sclp_init_state_uninitialized;
+	free_page((unsigned long) sclp_read_sccb);
+	free_page((unsigned long) sclp_init_sccb);
 fail_unlock:
 	spin_unlock_irqrestore(&sclp_lock, flags);
 	return rc;