selftests/mm: fix va_high_addr_switch.sh failure on x86_64

JIRA: https://issues.redhat.com/browse/RHEL-130531

commit c563252
Author: Chunyu Hu <chuhu@redhat.com>
Date:   Fri Sep 12 09:37:11 2025 +0800

    selftests/mm: fix va_high_addr_switch.sh failure on x86_64

    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 cc92882 ("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 cc92882 ("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, change to choose the last
    hugepage aligned address within the DEFAULT_MAP_WINDOW as the hint addr,
    and the addr + len (2 hugepages) will be one hugepage above the
    DEFAULT_MAP_WINDOW.  An aligned address won't be affected by the page
    round up or round down from kernel, so it's determistic.

    Link: https://lkml.kernel.org/r/20250912013711.3002969-4-chuhu@redhat.com
    Fixes: cc92882 ("mm: drop hugetlb_get_unmapped_area{_*} functions")
    Signed-off-by: Chunyu Hu <chuhu@redhat.com>
    Suggested-by: David Hildenbrand <david@redhat.com>
    Acked-by: David Hildenbrand <david@redhat.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Signed-off-by: Chunyu Hu <chuhu@redhat.com>

Author: Chunyu-Hu

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 - 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 - hugepagesize, 2*hugepagesize, MAP_HUGETLB)",
 			.low_addr_required = 1,
 			.keep_mapped = 1,
 		},