+ selftests-mm-fix-va_high_addr_switchsh-failure-on-x86_64.patch added to mm-new branch

+ selftests-mm-fix-va_high_addr_switchsh-failure-on-x86_64.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: selftests/mm: fix va_high_addr_switch.sh failure on x86_64
has been added to the -mm mm-new branch.  Its filename is
     selftests-mm-fix-va_high_addr_switchsh-failure-on-x86_64.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-mm-fix-va_high_addr_switchsh-failure-on-x86_64.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days

------------------------------------------------------
From: Chunyu Hu <chuhu@redhat.com>
Subject: selftests/mm: fix va_high_addr_switch.sh failure on x86_64
Date: Mon, 8 Sep 2025 20:47:39 +0800

The test will fail as below on x86_64 with cpu la57 support (will skip if
no la57 support).  Note, the test requries nr_hugepages to be set first.

  # running bash ./va_high_addr_switch.sh
  # -------------------------------------
  # mmap(addr_switch_hint - pagesize, pagesize): 0x7f55b60fa000 - OK
  # mmap(addr_switch_hint - pagesize, (2 * pagesize)): 0x7f55b60f9000 - OK
  # mmap(addr_switch_hint, pagesize): 0x800000000000 - OK
  # mmap(addr_switch_hint, 2 * pagesize, MAP_FIXED): 0x800000000000 - OK
  # mmap(NULL): 0x7f55b60f9000 - OK
  # mmap(low_addr): 0x40000000 - OK
  # mmap(high_addr): 0x1000000000000 - OK
  # mmap(high_addr) again: 0xffff55b6136000 - OK
  # mmap(high_addr, MAP_FIXED): 0x1000000000000 - OK
  # mmap(-1): 0xffff55b6134000 - OK
  # mmap(-1) again: 0xffff55b6132000 - OK
  # mmap(addr_switch_hint - pagesize, pagesize): 0x7f55b60fa000 - OK
  # mmap(addr_switch_hint - pagesize, 2 * pagesize): 0x7f55b60f9000 - OK
  # mmap(addr_switch_hint - pagesize/2 , 2 * pagesize): 0x7f55b60f7000 - OK
  # mmap(addr_switch_hint, pagesize): 0x800000000000 - OK
  # mmap(addr_switch_hint, 2 * pagesize, MAP_FIXED): 0x800000000000 - OK
  # mmap(NULL, MAP_HUGETLB): 0x7f55b5c00000 - OK
  # mmap(low_addr, MAP_HUGETLB): 0x40000000 - OK
  # mmap(high_addr, MAP_HUGETLB): 0x1000000000000 - OK
  # mmap(high_addr, MAP_HUGETLB) again: 0xffff55b5e00000 - OK
  # mmap(high_addr, MAP_FIXED | MAP_HUGETLB): 0x1000000000000 - OK
  # mmap(-1, MAP_HUGETLB): 0x7f55b5c00000 - OK
  # mmap(-1, MAP_HUGETLB) again: 0x7f55b5a00000 - OK
  # mmap(addr_switch_hint - pagesize, 2*hugepagesize, MAP_HUGETLB): 0x800000000000 - FAILED
  # mmap(addr_switch_hint , 2*hugepagesize, MAP_FIXED | MAP_HUGETLB): 0x800000000000 - OK
  # [FAIL]

addr_switch_hint is defined as DFEFAULT_MAP_WINDOW in the failed test (for
x86_64, DFEFAULT_MAP_WINDOW is defined as (1UL<<47) - pagesize) in 64 bit.

Before commit cc92882ee218 ("mm: drop hugetlb_get_unmapped_area{_*}
functions"), for x86_64 hugetlb_get_unmapped_area() is handled in arch
code arch/x86/mm/hugetlbpage.c and addr is checked with
map_address_hint_valid() after align with 'addr &= huge_page_mask(h)'
which is a round down way, and it will fail the check because the addr is
within the DEFAULT_MAP_WINDOW but (addr + len) is above the
DFEFAULT_MAP_WINDOW.  So it wil go through the
hugetlb_get_unmmaped_area_top_down() to find an area within the
DFEFAULT_MAP_WINDOW.

After commit cc92882ee218 ("mm: drop hugetlb_get_unmapped_area{_*}
functions").  The addr hint for hugetlb_get_unmmaped_area() will be
rounded up and aligned to hugepage size with ALIGN() for all arches.  And
after the align, the addr will be above the default MAP_DEFAULT_WINDOW,
and the map_addresshint_valid() check will pass because both aligned addr
(addr0) and (addr + len) are above the DEFAULT_MAP_WINDOW, and the aligned
hint address (0x800000000000) is returned as an suitable gap is found
there, in arch_get_unmapped_area_topdown().

To still cover the case that addr is within the DEFAULT_MAP_WINDOW, and
addr + len is above the DFEFAULT_MAP_WINDOW, make the addr hint one
hugepage lower, so that after the align it's still within
DEFAULT_MAP_WINDOW, and the addr + len (2 hugepages) will be above
DEFAULT_MAP_WINDOW.

Link: https://lkml.kernel.org/r/20250908124740.2946005-4-chuhu@redhat.com
Fixes: cc92882ee218 ("mm: drop hugetlb_get_unmapped_area{_*} functions")
Signed-off-by: Chunyu Hu <chuhu@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/mm/va_high_addr_switch.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/tools/testing/selftests/mm/va_high_addr_switch.c~selftests-mm-fix-va_high_addr_switchsh-failure-on-x86_64
+++ a/tools/testing/selftests/mm/va_high_addr_switch.c
@@ -230,10 +230,10 @@ void testcases_init(void)
 			.msg = "mmap(-1, MAP_HUGETLB) again",
 		},
 		{
-			.addr = (void *)(addr_switch_hint - pagesize),
+			.addr = (void *)(addr_switch_hint - pagesize - hugepagesize),
 			.size = 2 * hugepagesize,
 			.flags = MAP_HUGETLB | MAP_PRIVATE | MAP_ANONYMOUS,
-			.msg = "mmap(addr_switch_hint - pagesize, 2*hugepagesize, MAP_HUGETLB)",
+			.msg = "mmap(addr_switch_hint - pagesize - hugepagesize, 2*hugepagesize, MAP_HUGETLB)",
 			.low_addr_required = 1,
 			.keep_mapped = 1,
 		},
_

Patches currently in -mm which might be from chuhu@redhat.com are

selftests-mm-fix-hugepages-cleanup-too-early.patch
selftests-mm-alloc-hugepages-in-va_high_addr_switch-test.patch
selftests-mm-fix-va_high_addr_switchsh-failure-on-x86_64.patch