x86: memblock: set current limit to max low memory address

The memblock current limit value is used to limit early boot memory
allocations below max low memory address by default, as the kernel can
access only to the low memory.

Hence, set memblock current limit value to the max mapped low memory
address instead of max mapped memory address.

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Grygorii Strashko <grygorii.strashko@ti.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/include/asm/page_types.h

@@ -51,9 +51,9 @@ extern int devmem_is_allowed(unsigned long pagenr);
 extern unsigned long max_low_pfn_mapped;
 extern unsigned long max_pfn_mapped;
 
-static inline phys_addr_t get_max_mapped(void)
+static inline phys_addr_t get_max_low_mapped(void)
 {
-	return (phys_addr_t)max_pfn_mapped << PAGE_SHIFT;
+	return (phys_addr_t)max_low_pfn_mapped << PAGE_SHIFT;
 }
 
 bool pfn_range_is_mapped(unsigned long start_pfn, unsigned long end_pfn);

arch/x86/kernel/setup.c

@@ -1119,7 +1119,7 @@ void __init setup_arch(char **cmdline_p)
 
 	setup_real_mode();
 
-	memblock_set_current_limit(get_max_mapped());
+	memblock_set_current_limit(get_max_low_mapped());
 	dma_contiguous_reserve(0);
 
 	/*