s390/sclp: reserve memory occupied by sclp early buffer

The memory block occupied by the SCLP early buffer that is allocated
by the decompressor and then handed over to the decompressed kernel,
must be reserved to prevent it from being reused for other purposes.
This is necessary because the SCLP early buffer is still in use
during kernel initialization.

Fixes: f1d3c532 ("s390/boot: move sclp early buffer from fixed address in asm to C")
Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Reported-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/include/asm/sclp.h

@@ -115,6 +115,8 @@ struct zpci_report_error_header {
 	u8 data[0];	/* Subsequent Data passed verbatim to SCLP ET 24 */
 } __packed;
 
+extern char *sclp_early_sccb;
+
 void sclp_early_set_buffer(void *sccb);
 int sclp_early_read_info(void);
 int sclp_early_read_storage_info(void);

arch/s390/kernel/setup.c

@@ -793,6 +793,7 @@ static void __init reserve_kernel(void)
 	unsigned long start_pfn = PFN_UP(__pa(_end));
 
 	memblock_reserve(0, STARTUP_NORMAL_OFFSET);
+	memblock_reserve((unsigned long)sclp_early_sccb, EXT_SCCB_READ_SCP);
 	memblock_reserve((unsigned long)_stext, PFN_PHYS(start_pfn)
 			 - (unsigned long)_stext);
 }

drivers/s390/char/sclp.h

@@ -310,8 +310,6 @@ extern int sclp_console_drop;
 extern unsigned long sclp_console_full;
 extern bool sclp_mask_compat_mode;
 
-extern char *sclp_early_sccb;
-
 void sclp_early_wait_irq(void);
 int sclp_early_cmd(sclp_cmdw_t cmd, void *sccb);
 unsigned int sclp_early_con_check_linemode(struct init_sccb *sccb);