From: Mike Rapoport <rppt@xxxxxxxxxxxxx> commit 5c279c4cf206e03995e04fd3404fa95ffd243a97 upstream. This reverts commit bde9cfa3afe4324ec251e4af80ebf9b7afaf7afe. 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: Mike Rapoport <rppt@xxxxxxxxxxxxx> Cc: stable@xxxxxxxxxx Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/kernel/setup.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -666,6 +666,17 @@ static void __init trim_platform_memory_ 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. * take them out. @@ -722,15 +733,6 @@ early_param("reservelow", parse_reservel 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)); }
