[PATCH v2 0/3] Fix va_high_addr_switch.sh test failure

[PATCH v2 0/3] Fix va_high_addr_switch.sh test failure

[Chunyu Hu]

The three patches fix the va_high_addr_switch.sh test failure on x86_64.

Patch 1 fixes the hugepage setup issue that nr_hugepages is reset too
early in run_vmtests.sh and break the later va_high_addr_switch testing.

Patch 2 adds hugepage setup in va_high_addr_switch test, so that it can
still work if vm_runtests.sh changes the hugepage setup someday.

Patch 3 fixes the test failure caused by the hint addr align method change
in hugetlb_get_unmapped_area().

Changes in v2:
 - patch 1 renames nr_hugepgs_origin to orig_nr_hugepgs
 - add a patch 2 to setup hugeapges in va_high_addr_switch test

Chunyu Hu (3):
  selftests/mm: fix hugepages cleanup too early
  selftests/mm: alloc hugepages in va_high_addr_switch test
  selftests/mm: fix va_high_addr_switch.sh failure on x86_64

 tools/testing/selftests/mm/run_vmtests.sh     |  9 ++++-
 .../selftests/mm/va_high_addr_switch.c        |  4 +-
 .../selftests/mm/va_high_addr_switch.sh       | 37 +++++++++++++++++++
 3 files changed, 46 insertions(+), 4 deletions(-)

-- 
2.49.0

[PATCH v2 1/3] selftests/mm: fix hugepages cleanup too early

[Chunyu Hu]

The nr_hugepgs variable is used to keep the original nr_hugepages at the
hugepage setup step at test beginning. After userfaultfd test, a cleaup is
executed, both /sys/kernel/mm/hugepages/hugepages-*/nr_hugepages and
/proc/sys//vm/nr_hugepages are reset to 'original' value before userfaultfd
test starts.

Issue here is the value used to restore /proc/sys/vm/nr_hugepages is
nr_hugepgs which is the initial value before the vm_runtests.sh runs, not
the value before userfaultfd test starts. 'va_high_addr_swith.sh' tests
runs after that will possibly see no hugepages available for test, and got
EINVAL when mmap(HUGETLB), making the result invalid.

And before pkey tests, nr_hugepgs is changed to be used as a temp variable
to save nr_hugepages before pkey test, and restore it after pkey tests
finish. The original nr_hugepages value is not tracked anymore, so no way
to restore it after all tests finish.

Add a new variable orig_nr_hugepgs to save the original nr_hugepages, and
and restore it to nr_hugepages after all tests finish. And change to use
the nr_hugepgs variable to save the /proc/sys/vm/nr_hugeages after hugepage
setup, it's also the value before userfaultfd test starts, and the correct
value to be restored after userfaultfd finishes. The va_high_addr_switch.sh
broken will be resolved.

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

---
Changes in v2
 - rename nr_hugepgs_origin to orig_nr_hugepgs
---
 tools/testing/selftests/mm/run_vmtests.sh | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
index 471e539d82b8..9866e4221bc2 100755
--- a/tools/testing/selftests/mm/run_vmtests.sh
+++ b/tools/testing/selftests/mm/run_vmtests.sh
@@ -172,13 +172,13 @@ fi
 
 # set proper nr_hugepages
 if [ -n "$freepgs" ] && [ -n "$hpgsize_KB" ]; then
-	nr_hugepgs=$(cat /proc/sys/vm/nr_hugepages)
+	orig_nr_hugepgs=$(cat /proc/sys/vm/nr_hugepages)
 	needpgs=$((needmem_KB / hpgsize_KB))
 	tries=2
 	while [ "$tries" -gt 0 ] && [ "$freepgs" -lt "$needpgs" ]; do
 		lackpgs=$((needpgs - freepgs))
 		echo 3 > /proc/sys/vm/drop_caches
-		if ! echo $((lackpgs + nr_hugepgs)) > /proc/sys/vm/nr_hugepages; then
+		if ! echo $((lackpgs + orig_nr_hugepgs)) > /proc/sys/vm/nr_hugepages; then
 			echo "Please run this test as root"
 			exit $ksft_skip
 		fi
@@ -189,6 +189,7 @@ if [ -n "$freepgs" ] && [ -n "$hpgsize_KB" ]; then
 		done < /proc/meminfo
 		tries=$((tries - 1))
 	done
+	nr_hugepgs=$(cat /proc/sys/vm/nr_hugepages)
 	if [ "$freepgs" -lt "$needpgs" ]; then
 		printf "Not enough huge pages available (%d < %d)\n" \
 		       "$freepgs" "$needpgs"
@@ -532,6 +533,10 @@ CATEGORY="page_frag" run_test ./test_page_frag.sh aligned
 
 CATEGORY="page_frag" run_test ./test_page_frag.sh nonaligned
 
+if [ "${HAVE_HUGEPAGES}" = 1 ]; then
+	echo "$orig_nr_hugepgs" > /proc/sys/vm/nr_hugepages
+fi
+
 echo "SUMMARY: PASS=${count_pass} SKIP=${count_skip} FAIL=${count_fail}" | tap_prefix
 echo "1..${count_total}" | tap_output
 
-- 
2.49.0

[PATCH v2 2/3] selftests/mm: alloc hugepages in va_high_addr_switch test

[Chunyu Hu]

Alloc hugepages in the test internally, so we don't fully rely on the
run_vmtests.sh. If run_vmtests.sh does that great, free hugepages is
enough for being used to run the test, leave it as it is, otherwise setup
the hugepages in the test.

Save the original nr_hugepages value and restore it after test finish, so
leave a stable test envronment.

Signed-off-by: Chunyu Hu <chuhu@redhat.com>
---
 .../selftests/mm/va_high_addr_switch.sh       | 37 +++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/tools/testing/selftests/mm/va_high_addr_switch.sh b/tools/testing/selftests/mm/va_high_addr_switch.sh
index 325de53966b6..a7d4b02b21dd 100755
--- a/tools/testing/selftests/mm/va_high_addr_switch.sh
+++ b/tools/testing/selftests/mm/va_high_addr_switch.sh
@@ -9,6 +9,7 @@
 
 # Kselftest framework requirement - SKIP code is 4.
 ksft_skip=4
+orig_nr_hugepages=0
 
 skip()
 {
@@ -76,5 +77,41 @@ check_test_requirements()
 	esac
 }
 
+save_nr_hugepages()
+{
+	orig_nr_hugepages=$(cat /proc/sys/vm/nr_hugepages)
+}
+
+restore_nr_hugepages()
+{
+	echo "$orig_nr_hugepages" > /proc/sys/vm/nr_hugepages
+}
+
+setup_nr_hugepages()
+{
+	local needpgs=$1
+	while read -r name size unit; do
+		if [ "$name" = "HugePages_Free:" ]; then
+			freepgs="$size"
+			break
+		fi
+	done < /proc/meminfo
+	if [ "$freepgs" -ge "$needpgs" ]; then
+		return
+	fi
+	local hpgs=$((orig_nr_hugepages + needpgs))
+	echo $hpgs > /proc/sys/vm/nr_hugepages
+
+	local nr_hugepgs=$(cat /proc/sys/vm/nr_hugepages)
+	if [ "$nr_hugepgs" != "$hpgs" ]; then
+		restore_nr_hugepages
+		skip "$0: no enough hugepages for testing"
+	fi
+}
+
 check_test_requirements
+save_nr_hugepages
+# 4 keep_mapped pages, and one for tmp usage
+setup_nr_hugepages 5
 ./va_high_addr_switch --run-hugetlb
+restore_nr_hugepages
-- 
2.49.0

[PATCH v2 3/3] selftests/mm: fix va_high_addr_switch.sh failure on x86_64

[Chunyu Hu]

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 <chuhu@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),
 			.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,
 		},
-- 
2.49.0

Re: [PATCH v2 1/3] selftests/mm: fix hugepages cleanup too early

[David Hildenbrand]

On 08.09.25 14:47, Chunyu Hu wrote:
> The nr_hugepgs variable is used to keep the original nr_hugepages at the
> hugepage setup step at test beginning. After userfaultfd test, a cleaup is
> executed, both /sys/kernel/mm/hugepages/hugepages-*/nr_hugepages and
> /proc/sys//vm/nr_hugepages are reset to 'original' value before userfaultfd
> test starts.
> 
> Issue here is the value used to restore /proc/sys/vm/nr_hugepages is
> nr_hugepgs which is the initial value before the vm_runtests.sh runs, not
> the value before userfaultfd test starts. 'va_high_addr_swith.sh' tests
> runs after that will possibly see no hugepages available for test, and got
> EINVAL when mmap(HUGETLB), making the result invalid.
> 
> And before pkey tests, nr_hugepgs is changed to be used as a temp variable
> to save nr_hugepages before pkey test, and restore it after pkey tests
> finish. The original nr_hugepages value is not tracked anymore, so no way
> to restore it after all tests finish.
> 
> Add a new variable orig_nr_hugepgs to save the original nr_hugepages, and
> and restore it to nr_hugepages after all tests finish. And change to use
> the nr_hugepgs variable to save the /proc/sys/vm/nr_hugeages after hugepage
> setup, it's also the value before userfaultfd test starts, and the correct
> value to be restored after userfaultfd finishes. The va_high_addr_switch.sh
> broken will be resolved.
> 
> Signed-off-by: Chunyu Hu <chuhu@redhat.com>
> 

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers

David / dhildenb

Re: [PATCH v2 3/3] selftests/mm: fix va_high_addr_switch.sh failure on x86_64

[David Hildenbrand]

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 <chuhu@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

Re: [PATCH v2 3/3] selftests/mm: fix va_high_addr_switch.sh failure on x86_64

[Chunyu Hu]

On Mon, Sep 08, 2025 at 03:09:24PM +0200, David Hildenbrand wrote:
> 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 <chuhu@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

Thanks for the review!

This is good idea and it would be more deterministic if we provide an
aligned address directly, then the kernel change won't affect the test.

> 
> 
> But now I realize that, likely,
> 
> 	.addr = (void *)(addr_switch_hint - hugepagesize),
> 
> would just work and be aligned?

Yes, it's aligned to the hugepagesize, align down and works. I prefer
this way as it's easier and all other tests in the file do like this.
Thanks for the suggestion.

I thought we would lose some test coverage on testing if it will work when
an un-hugepagesize aligned addr is provided. Do you think it's
necessary? If not, I'll change to:

	.addr = (void *)(addr_switch_hint - hugepagesize),

or we can add them both if necesasry.

> 
> -- 
> Cheers
> 
> David / dhildenb
>