The patch titled
Subject: mm/sparse: set SECTION_NID_SHIFT to 6
has been added to the -mm tree. Its filename is
mm-sparse-set-section_nid_shift-to-6.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-sparse-set-section_nid_shift-to-6.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-sparse-set-section_nid_shift-to-6.patch
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From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Subject: mm/sparse: set SECTION_NID_SHIFT to 6
Currently SECTION_NID_SHIFT is set to 3, which is incorrect because bit 3
and 4 can be overlapped by sub-field for early NID, and can be
unexpectedly set on NUMA systems. There are a few non-critical issues
related to this:
- Having SECTION_TAINT_ZONE_DEVICE set for wrong sections forces
pfn_to_online_page() through the slow path, but doesn't actually break
the kernel.
- A kdump generation tool like makedumpfile uses this field to calculate
the physical address to read. So wrong bits can make the tool access to
wrong address and fail to create kdump. This can be avoided by the
tool, so it's not critical.
To fix it, set SECTION_NID_SHIFT to 6 which is the minimum number of
available bits of section flag field.
Link: https://lkml.kernel.org/r/20210707045548.810271-1-naoya.horiguchi@xxxxxxxxx
Fixes: 1f90a3477df3 ("mm: teach pfn_to_online_page() about ZONE_DEVICE section collisions")
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Reported-by: Kazuhito Hagio <k-hagio-ab@xxxxxxx>
Suggested-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Wang Wensheng <wangwensheng4@xxxxxxxxxx>
Cc: Rui Xiang <rui.xiang@xxxxxxxxxx>
Cc: Kazu <k-hagio-ab@xxxxxxx>
Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mmzone.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/include/linux/mmzone.h~mm-sparse-set-section_nid_shift-to-6
+++ a/include/linux/mmzone.h
@@ -1364,7 +1364,7 @@ extern size_t mem_section_usage_size(voi
#define SECTION_TAINT_ZONE_DEVICE (1UL<<4)
#define SECTION_MAP_LAST_BIT (1UL<<5)
#define SECTION_MAP_MASK (~(SECTION_MAP_LAST_BIT-1))
-#define SECTION_NID_SHIFT 3
+#define SECTION_NID_SHIFT 6
static inline struct page *__section_mem_map_addr(struct mem_section *section)
{
_
Patches currently in -mm which might be from naoya.horiguchi@xxxxxxx are
mm-sparse-set-section_nid_shift-to-6.patch
