linux/arch
Mike Rapoport bde9cfa3af x86/setup: don't remove E820_TYPE_RAM for pfn 0
Patch series "mm: fix initialization of struct page for holes in  memory layout", v3.

Commit 73a6e474cb ("mm: memmap_init: iterate over memblock regions
rather that check each PFN") exposed several issues with the memory map
initialization and these patches fix those issues.

Initially there were crashes during compaction that Qian Cai reported
back in April [1].  It seemed back then that the problem was fixed, but
a few weeks ago Andrea Arcangeli hit the same bug [2] and there was an
additional discussion at [3].

[1] https://lore.kernel.org/lkml/8C537EB7-85EE-4DCF-943E-3CC0ED0DF56D@lca.pw
[2] https://lore.kernel.org/lkml/20201121194506.13464-1-aarcange@redhat.com
[3] https://lore.kernel.org/mm-commits/20201206005401.qKuAVgOXr%akpm@linux-foundation.org

This patch (of 2):

The first 4Kb of memory is a BIOS owned area and to avoid its allocation
for the kernel it was not listed in e820 tables as memory.  As the result,
pfn 0 was never recognised by the generic memory management and it is not
a part of neither node 0 nor ZONE_DMA.

If set_pfnblock_flags_mask() would be ever called for the pageblock
corresponding to the first 2Mbytes of memory, having pfn 0 outside of
ZONE_DMA would trigger

	VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn), page);

Along with reserving the first 4Kb in e820 tables, several first pages are
reserved with memblock in several places during setup_arch().  These
reservations are enough to ensure the kernel does not touch the BIOS area
and it is not necessary to remove E820_TYPE_RAM for pfn 0.

Remove the update of e820 table that changes the type of pfn 0 and move
the comment describing why it was done to trim_low_memory_range() that
reserves the beginning of the memory.

Link: https://lkml.kernel.org/r/20210111194017.22696-2-rppt@kernel.org
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Qian Cai <cai@lca.pw>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-01-24 09:20:52 -08:00
..
alpha local64.h: make <asm/local64.h> mandatory 2020-12-29 15:36:49 -08:00
arc ARC: [hsdk]: Enable FPU_SAVE_RESTORE 2021-01-08 13:46:58 -08:00
arm xen: branch for v5.11-rc4 2021-01-15 10:52:00 -08:00
arm64 arm64: kprobes: Fix Uexpected kernel BRK exception at EL1 2021-01-22 16:05:29 +00:00
c6x tif-task_work.arch-2020-12-14 2020-12-16 12:33:35 -08:00
csky local64.h: make <asm/local64.h> mandatory 2020-12-29 15:36:49 -08:00
h8300 local64.h: make <asm/local64.h> mandatory 2020-12-29 15:36:49 -08:00
hexagon local64.h: make <asm/local64.h> mandatory 2020-12-29 15:36:49 -08:00
ia64 ia64: fix build failure caused by memory model changes 2021-01-17 13:31:09 +02:00
m68k local64.h: make <asm/local64.h> mandatory 2020-12-29 15:36:49 -08:00
microblaze local64.h: make <asm/local64.h> mandatory 2020-12-29 15:36:49 -08:00
mips - fix coredumps on 64bit kernels 2021-01-15 13:07:33 -08:00
nds32 local64.h: make <asm/local64.h> mandatory 2020-12-29 15:36:49 -08:00
nios2 tif-task_work.arch-2020-12-14 2020-12-16 12:33:35 -08:00
openrisc openrisc: io: Add missing __iomem annotation to iounmap() 2021-01-20 06:14:26 +09:00
parisc local64.h: make <asm/local64.h> mandatory 2020-12-29 15:36:49 -08:00
powerpc powerpc/vdso: Fix clock_gettime_fallback for vdso32 2021-01-14 15:56:44 +11:00
riscv RISC-V: Fix maximum allowed phsyical memory for RV32 2021-01-15 21:35:48 -08:00
s390 Merge branch 'kvm-master' into kvm-next 2021-01-07 18:06:52 -05:00
sh local64.h: make <asm/local64.h> mandatory 2020-12-29 15:36:49 -08:00
sparc local64.h: make <asm/local64.h> mandatory 2020-12-29 15:36:49 -08:00
um This pull request contains the following changes for UML: 2020-12-17 17:56:44 -08:00
x86 x86/setup: don't remove E820_TYPE_RAM for pfn 0 2021-01-24 09:20:52 -08:00
xtensa local64.h: make <asm/local64.h> mandatory 2020-12-29 15:36:49 -08:00
.gitignore
Kconfig fanotify: Fix sys_fanotify_mark() on native x86-32 2020-12-28 11:58:59 +01:00