On 08.09.25 14:47, Chunyu Hu wrote:
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.
Fixes: cc92882ee218 ("mm: drop hugetlb_get_unmapped_area{_*} functions")
Signed-off-by: Chunyu Hu <ch...@redhat.com>
---
tools/testing/selftests/mm/va_high_addr_switch.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/mm/va_high_addr_switch.c
b/tools/testing/selftests/mm/va_high_addr_switch.c
index 896b3f73fc53..bd96dc3b5931 100644
--- a/tools/testing/selftests/mm/va_high_addr_switch.c
+++ b/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),
Wouldn't it be more deterministic to do the alignment/rounding ourselves?
(void *)(ALIGN_DOWN(addr_switch_hint - pagesize), hugepagesize)
Unfortunately we don't have an ALIGN_DOWN helper available yet.
We could just move the one in pkey-helpers.h into vm_util.h
But now I realize that, likely,
.addr = (void *)(addr_switch_hint - hugepagesize),
would just work and be aligned?
--
Cheers
David / dhildenb
