Commit 5c279c4c authored by Mike Rapoport's avatar Mike Rapoport Committed by Linus Torvalds
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Revert "x86/setup: don't remove E820_TYPE_RAM for pfn 0" 

This reverts commit bde9cfa3.

Changing the first memory page type from E820_TYPE_RESERVED to
E820_TYPE_RAM makes it a part of "System RAM" resource rather than a
reserved resource and this in turn causes devmem_is_allowed() to treat
is as area that can be accessed but it is filled with zeroes instead of
the actual data as previously.

The change in /dev/mem output causes lilo to fail as was reported at
slakware users forum, and probably other legacy applications will
experience similar problems.

Link: https://www.linuxquestions.org/questions/slackware-14/slackware-current-lilo-vesa-warnings-after-recent-updates-4175689617/#post6214439


Signed-off-by: default avatarMike Rapoport <rppt@linux.ibm.com>
Cc: stable@kernel.org
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 927002ed

arch/x86/kernel/setup.c

+11 −9
Original line number Diff line number Diff line
@@ -660,6 +660,17 @@ static void __init trim_platform_memory_ranges(void) 


static void __init trim_bios_range(void)

{

	/*

	 * A special case is the first 4Kb of memory;

	 * This is a BIOS owned area, not kernel ram, but generally

	 * not listed as such in the E820 table.

	 *

	 * This typically reserves additional memory (64KiB by default)

	 * since some BIOSes are known to corrupt low memory.  See the

	 * Kconfig help text for X86_RESERVE_LOW.

	 */

	e820__range_update(0, PAGE_SIZE, E820_TYPE_RAM, E820_TYPE_RESERVED);



	/*

	 * special case: Some BIOSes report the PC BIOS

	 * area (640Kb -> 1Mb) as RAM even though it is not.
@@ -717,15 +728,6 @@ early_param("reservelow", parse_reservelow); 


static void __init trim_low_memory_range(void)

{

	/*

	 * A special case is the first 4Kb of memory;

	 * This is a BIOS owned area, not kernel ram, but generally

	 * not listed as such in the E820 table.

	 *

	 * This typically reserves additional memory (64KiB by default)

	 * since some BIOSes are known to corrupt low memory.  See the

	 * Kconfig help text for X86_RESERVE_LOW.

	 */

	memblock_reserve(0, ALIGN(reserve_low, PAGE_SIZE));

}