s390/sclp: use only one sclp early buffer to send commands

A buffer that can be used for communication with SCLP is required
to lie below 2GB memory address. Therefore, both sclp_info_sccb
and sclp_early_sccb must fulfill this requirement if passed directly
to the sclp_early_cmd() function. Instead, use only sclp_early_sccb
for communication with SCLP. This allows the buffer sclp_info_sccb
to be placed anywhere in the memory address space and, therefore,
simplifies the process of making the decompressor relocatable later on,
one thing less to relocate. And make sure that the length of the new unified
early SCLP buffer is no less than the length of the removed sclp_info_sccb
buffer which might be larger than the length of the sclp_early_sccb buffer.

Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

1 files changed, 11 insertions, 1 deletions

diff --git a/drivers/s390/char/sclp_early_core.c b/drivers/s390/char/sclp_early_core.c
index b7329af076a0..80ba6523e76e 100644
--- a/drivers/s390/char/sclp_early_core.c
+++ b/drivers/s390/char/sclp_early_core.c
@@ -235,11 +235,20 @@ void sclp_early_printk(const char *str)
 	__sclp_early_printk(str, strlen(str));
 }
 
+/*
+ * We can't pass sclp_info_sccb to sclp_early_cmd() here directly,
+ * because it might not fulfil the requiremets for a SCLP communication buffer:
+ *   - lie below 2G in memory
+ *   - be page-aligned
+ * Therefore, we use the buffer sclp_early_sccb (which fulfils all those
+ * requirements) temporarily for communication and copy a received response
+ * back into the buffer sclp_info_sccb upon successful completion.
+ */
 int __init sclp_early_read_info(void)
 {
 	int i;
 	int length = test_facility(140) ? EXT_SCCB_READ_SCP : PAGE_SIZE;
-	struct read_info_sccb *sccb = &sclp_info_sccb;
+	struct read_info_sccb *sccb = (struct read_info_sccb *)sclp_early_sccb;
 	sclp_cmdw_t commands[] = {SCLP_CMDW_READ_SCP_INFO_FORCED,
 				  SCLP_CMDW_READ_SCP_INFO};
 
@@ -251,6 +260,7 @@ int __init sclp_early_read_info(void)
 		if (sclp_early_cmd(commands[i], sccb))
 			break;
 		if (sccb->header.response_code == 0x10) {
+			memcpy(&sclp_info_sccb, sccb, length);
 			sclp_info_sccb_valid = 1;
 			return 0;
 		}