From nobody Fri Sep 25 12:06:10 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id D60AF39792B; Tue, 15 Sep 2026 09:21:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789464116; cv=none; b=huTOOCAML/BZ/6KsQIzQObzDI4PG3/2paFRhl2ql/sGGtu6e8kOo1By30J3a5/Me8GKccBOnzoj+OKQ9RCBkVRPy7vbd8eYBF+4kR4Zu/nqpx+ZjNdAIfa284Owoa5TaIWQnwbKMQPZbFOX7d4+k1qYyd29Ooo+0jIYe0idgU9o= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789464116; c=relaxed/simple; bh=D8etrFh5PGy5HLvPhwqGM1Wl5RU8d5sdnQrtvxeo55k=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=ovE1s7GBV346eqNEbVAuiCD/skPpjgmBUtYwANEp4/n5XbTkrw6igRmZHfnLUp4gwNe4TW60ma27DuuxOL4qiskHrdWXPGhElndk1Kee35LRlH8ySGB8Ervm0pGtn44i8+kov8pW6PwJHlywbdi6lQBUfeF/6P740mp1BAEEA0c= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=p4rMo+IJ; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="p4rMo+IJ" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 63483169E; Tue, 15 Sep 2026 02:21:49 -0700 (PDT) Received: from e129823.arm.com (e129823.arm.com [10.2.213.3]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0F3F93F86F; Tue, 15 Sep 2026 02:21:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1789464113; bh=D8etrFh5PGy5HLvPhwqGM1Wl5RU8d5sdnQrtvxeo55k=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=p4rMo+IJ/Gkhmw6l4doFJOhI3kq5Jsrz6oPJZQHc42wSQRksETR+uZr0N63rimdPT TulTZLc1rZ7RX5Uo2fH7NNx47T6wNGRrtEkh4ryD1XR5bYqV0pzgpeiWYhM0iI144d fz13VfZSG3KjlMxrf7pKTlhU4YDzO7wL/2D02w1I= From: Yeoreum Yun Date: Tue, 15 Sep 2026 10:21:36 +0100 Subject: [PATCH 1/2] kselftest: mm: return fail when child test result is fail in khugepaged Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260915-fix_khugepagd_fail-v1-1-bb6f04c8759f@arm.com> References: <20260915-fix_khugepagd_fail-v1-0-bb6f04c8759f@arm.com> In-Reply-To: <20260915-fix_khugepagd_fail-v1-0-bb6f04c8759f@arm.com> To: Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Lorenzo Stoakes , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Andrew Morton , David Hildenbrand , Shuah Khan , Yeoreum Yun X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3364; i=yeoreum.yun@arm.com; h=from:subject:message-id; bh=D8etrFh5PGy5HLvPhwqGM1Wl5RU8d5sdnQrtvxeo55k=; b=owEB7QES/pANAwAKAW3Vw9FaxTEzAcsmYgBqqQ4pqgL4yB1OOTyqBCX0ujLg4uw+AK27HNSUj klNmhjYVguJAbMEAAEKAB0WIQQtg+CS3QUzuFh1pJ1t1cPRWsUxMwUCaqkOKQAKCRBt1cPRWsUx M9jODAC1p2pD+ImErVv4cHBblEws2o83F5MqG+kFAp3hq2sM3JAWDCTu/5rzPSZ96XYiCOJhGfQ Rz1CgascbrrgUX2lkNITzBJZxvDWiN3vHHkFSDHAq7vN0Nb1JX/FwmMDbUGU6sokZ/crr7W6B0E G6uz2lKxu5jE1uaNPROWId6JjXzJN8H2Tk3JQQFCPb/fwWOxZQ9lo1i07Xj4WiNkR/NhfeurO/m YhBJ4okasmpw3TKuufoFso92MjiKWPoZHJY89APsnRUuE808RM4W0m3+X2MPEdoHgJv87iNzuIp mlE7lt1w9eHwawcgv1VKEtNtN/BfFLuVSOoC/2IqrIvFwEoQr1A4MBCDO/moKVMRO82eYnFoX0j EX2FBnBXoIuILwFvQIDXGgCBC/hayweE+WrJL1J2iGBky7rP649fMnf9lsQZEwSatQDRw7ZfVaR AFpGz+ZgIS5jCcn7qJr2/3bbGw7p2VjhBZXC6ewfU63Kf22QhYcek+UTvZ0FuUZaIsKf4= X-Developer-Key: i=yeoreum.yun@arm.com; a=openpgp; fpr=2D83E092DD0533B85875A49D6DD5C3D15AC53133 Although the child process in collapse_fork*() or collapse_max_ptes_shared() reports `KSFT_FAIL`, the result is ignored because the test only checks whether the parent=E2=80=99s page was collapsed into a huge page. As a result, the test is considered successful whenever the parent=E2=80=99= s page is a huge page, even if the child test fails, as shown below: # # Run test: collapse_max_ptes_shared (khugepaged:anon) # Allocate huge page... OK # Share huge page over fork()... OK # Trigger CoW on page 1023 of 2048... OK # Maybe collapse with max_ptes_shared exceeded.... OK # Trigger CoW on page 1024 of 2048... Fail Bail out! Unexpected huge page # Planned tests !=3D run tests (26 !=3D 23) # Totals: pass:23 fail:0 xfail:0 xpass:0 skip:0 error:0 // child failed. # Check if parent still has huge page... OK // parent hpage = success ok 24 collapse_max_ptes_shared // considered as= success ... # Totals: pass:26 fail:0 xfail:0 xpass:0 skip:0 error:0 To address this, propagate the child=E2=80=99s failure and skip the subsequ= ent check in the parent. Signed-off-by: Yeoreum Yun --- tools/testing/selftests/mm/khugepaged.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selfte= sts/mm/khugepaged.c index f82673f5f6b47..c32244b565658 100644 --- a/tools/testing/selftests/mm/khugepaged.c +++ b/tools/testing/selftests/mm/khugepaged.c @@ -1009,6 +1009,8 @@ static void collapse_fork(struct collapse_context *c,= struct mem_ops *ops) =20 wait(&wstatus); exit_status =3D WEXITSTATUS(wstatus); + if (exit_status =3D=3D KSFT_FAIL) + goto out; =20 ksft_print_msg("Check if parent still has small page..."); if (ops->check_huge(p, hpage_pmd_size, 0, hpage_pmd_size)) @@ -1016,6 +1018,7 @@ static void collapse_fork(struct collapse_context *c,= struct mem_ops *ops) else fail("Fail"); validate_memory(p, 0, page_size); +out: ops->cleanup_area(p, hpage_pmd_size); ksft_test_result_report(exit_status, "%s\n", __func__); } @@ -1056,6 +1059,8 @@ static void collapse_fork_compound(struct collapse_co= ntext *c, struct mem_ops *o =20 wait(&wstatus); exit_status =3D WEXITSTATUS(wstatus); + if (exit_status =3D=3D KSFT_FAIL) + goto out; =20 ksft_print_msg("Check if parent still has huge page..."); if (ops->check_huge(p, hpage_pmd_size, 1, hpage_pmd_size)) @@ -1063,6 +1068,7 @@ static void collapse_fork_compound(struct collapse_co= ntext *c, struct mem_ops *o else fail("Fail"); validate_memory(p, 0, hpage_pmd_size); +out: ops->cleanup_area(p, hpage_pmd_size); ksft_test_result_report(exit_status, "%s\n", __func__); } @@ -1114,6 +1120,8 @@ static void collapse_max_ptes_shared(struct collapse_= context *c, struct mem_ops =20 wait(&wstatus); exit_status =3D WEXITSTATUS(wstatus); + if (exit_status =3D=3D KSFT_FAIL) + goto out; =20 ksft_print_msg("Check if parent still has huge page..."); if (ops->check_huge(p, hpage_pmd_size, 1, hpage_pmd_size)) @@ -1121,6 +1129,7 @@ static void collapse_max_ptes_shared(struct collapse_= context *c, struct mem_ops else fail("Fail"); validate_memory(p, 0, hpage_pmd_size); +out: ops->cleanup_area(p, hpage_pmd_size); ksft_test_result_report(exit_status, "%s\n", __func__); } --=20 2.43.0 From nobody Fri Sep 25 12:06:10 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id DF762472F66; Tue, 15 Sep 2026 09:21:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789464119; cv=none; b=r2iJlRD+r4kJ4HipfnpaM3kpk21JgLP6JrnxqykCDQ/p8DKfVF+DDW6CeLfRQJAjk5B6vCWD49AIqdXE14IrSo8ZResWZvM3JDJ+8TmKSUdXI8Mg/ASKWo1hZqhLs9nUU6KgT6NREQilI52J4KhmmIs/+DODYS3jgv/Tspwh7wc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789464119; c=relaxed/simple; bh=yxQR2EiRSnlOGVI9wDjEBOU2jCM7zzSGFANR8dJ9rAs=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=WymIqiFVfL1TD2lfSWgWQQgEbFmmcRIrolmt3sVu5JTM9JQ94utRDkn/aoAj79F51azci9SidT1JGljNzr3PJAKd7aDfzfraQt2+slAg18AfGba4CDEQDVF5QkMEXe+OJ684MlznhS3z6Bo0gIbW1w4bzPqr1sQUVAYDAsfbo8U= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=J+kAJGL2; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="J+kAJGL2" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A9B1716F3; Tue, 15 Sep 2026 02:21:52 -0700 (PDT) Received: from e129823.arm.com (e129823.arm.com [10.2.213.3]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 52A473F86F; Tue, 15 Sep 2026 02:21:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1789464116; bh=yxQR2EiRSnlOGVI9wDjEBOU2jCM7zzSGFANR8dJ9rAs=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=J+kAJGL2BjHbdj6nYrlMZsL3L9Lj2PjwDM80cYWXHd1Vp1lOWJjcq7Q2Qm/j5XnHw OjgNB6wv7FOdPdyIcamVigwYNKsdDZGFctCFK0J3gYwPRK/VObjoS9MkLMoYsaBWd+ iOZ73SrYMpRizoPmYiqkSnm4/uZLMV/BOtsF+YYY= From: Yeoreum Yun Date: Tue, 15 Sep 2026 10:21:37 +0100 Subject: [PATCH 2/2] kselftest: mm: fix intermittent failure khugepaged test Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260915-fix_khugepagd_fail-v1-2-bb6f04c8759f@arm.com> References: <20260915-fix_khugepagd_fail-v1-0-bb6f04c8759f@arm.com> In-Reply-To: <20260915-fix_khugepagd_fail-v1-0-bb6f04c8759f@arm.com> To: Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Lorenzo Stoakes , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Andrew Morton , David Hildenbrand , Shuah Khan , Yeoreum Yun X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4423; i=yeoreum.yun@arm.com; h=from:subject:message-id; bh=yxQR2EiRSnlOGVI9wDjEBOU2jCM7zzSGFANR8dJ9rAs=; b=owEB7QES/pANAwAKAW3Vw9FaxTEzAcsmYgBqqQ4qQATMvvJEK3ZYgcRPUbjS+53++Tk8Ysis4 XDYAEUYOq6JAbMEAAEKAB0WIQQtg+CS3QUzuFh1pJ1t1cPRWsUxMwUCaqkOKgAKCRBt1cPRWsUx M78uC/9CIAfRf6zmk9YykwQpH7GNfMsVHT0Grsqco4DCwk9jbC2K1EPyUOVkW0gj+SOVAz1/CO0 mYO/mSYIKo6ElFDUjk1tg/UIANN7l2em3oLht51OtL6Mvj6Bb5ZYfWi1dTBpW+gp+0NTNBW1zER ejI7obz8sZUIuzHc5osND5TB9ClnKht4UKAcIYHSvtstrRj5Fpd5gejXxDVmiUkjCY/SVh0PVbw tX/4G46b+FvLKW5Z6XYUxTwpJGZXhdZUWZw6jj0GygVml0ZgEXG4kN+7Uj60v2C5+FG6Fe+yPxH mdZ62oyYjMykd6NiUqitvlkKtE64uhCNF+q18Jz72OWlv1/ZutO7xi0qkSrzHxBtUAnQ4TLjQJ2 4VTylKZKrAw4Dk74VkTlgui5x47mZW3zuRBYevCgvbOutVIppYF8XbIlb/C+ykVM2nOgWlcb4T1 RRWqJCj2bpT9Fn6qeA1coHIsV37cXOjbs0uI3u3zI7L15ZxPHBo1JWaSVDXUkyrEJDcm0= X-Developer-Key: i=yeoreum.yun@arm.com; a=openpgp; fpr=2D83E092DD0533B85875A49D6DD5C3D15AC53133 There are intermittent failures in collapse_max_ptes_swap() and collapse_max_ptes_shared() when using the khugepaged_context: // while running ./khugepaged -s 2 # Run test: collapse_max_ptes_shared (khugepaged:anon) # Allocate huge page... OK # Share huge page over fork()... OK # Trigger CoW on page 1023 of 2048... OK # Maybe collapse with max_ptes_shared exceeded.... OK # Trigger CoW on page 1024 of 2048... Fail Bail out! Unexpected huge page # Planned tests !=3D run tests (26 !=3D 23) # Totals: pass:23 fail:0 xfail:0 xpass:0 skip:0 error:0 # Run test: collapse_max_ptes_swap (khugepaged:anon) # Swapout 257 of 2048 pages... OK # Maybe collapse with max_ptes_swap exceeded.... OK # Swapout 256 of 2048 pages... OK Bail out! Unexpected huge page # Planned tests !=3D run tests (26 !=3D 17) # Totals: pass:17 fail:0 xfail:0 xpass:0 skip:0 error:0 This happens because khugepaged may collapse the pages before wait_for_scan= () is called, causing a sanity check that expects uncollapsed pages to fail. For example, in collapse_max_ptes_swap(), after faulting the pages back in and paging out up to max_ptes_swap pages, khugepaged may collapse them again before c->collapse() is called. To prevent this, change the khugepaged setting from ALWAYS to MADVICE for the affected tests, and mark the VMA with MADV_NOHUGEPAGE after it has been collapsed by wait_for_scan(). This prevents khugepaged from collapsing it again before c->collapse() is called. This failure was observed on NVIDIA Spark with 16KB page. Signed-off-by: Yeoreum Yun --- tools/testing/selftests/mm/khugepaged.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selfte= sts/mm/khugepaged.c index c32244b565658..83e9386bbc842 100644 --- a/tools/testing/selftests/mm/khugepaged.c +++ b/tools/testing/selftests/mm/khugepaged.c @@ -578,6 +578,8 @@ static bool wait_for_scan(const char *msg, char *p, siz= e_t len, usleep(TICK); } =20 + madvise(p, len, MADV_NOHUGEPAGE); + return timeout =3D=3D -1; } =20 @@ -839,6 +841,7 @@ static void collapse_swapin_single_pte(struct collapse_= context *c, struct mem_op =20 static void collapse_max_ptes_swap(struct collapse_context *c, struct mem_= ops *ops) { + struct thp_settings settings =3D *thp_current_settings(); int max_ptes_swap =3D thp_read_num("khugepaged/max_ptes_swap"); void *p; =20 @@ -860,6 +863,9 @@ static void collapse_max_ptes_swap(struct collapse_cont= ext *c, struct mem_ops *o validate_memory(p, 0, hpage_pmd_size); =20 if (c->enforce_pte_scan_limits) { + settings.hugepages[collapse_order].enabled =3D THP_MADVISE; + thp_push_settings(&settings); + ops->fault(p, 0, hpage_pmd_size); ksft_print_msg("Swapout %d of %d pages...", max_ptes_swap, hpage_pmd_nr); @@ -869,12 +875,15 @@ static void collapse_max_ptes_swap(struct collapse_co= ntext *c, struct mem_ops *o success("OK"); } else { fail("Fail"); + thp_pop_settings(); goto out; } =20 c->collapse("Collapse with max_ptes_swap pages swapped out", p, 1, ops, true); validate_memory(p, 0, hpage_pmd_size); + + thp_pop_settings(); } out: ops->cleanup_area(p, hpage_pmd_size); @@ -1075,6 +1084,7 @@ static void collapse_fork_compound(struct collapse_co= ntext *c, struct mem_ops *o =20 static void collapse_max_ptes_shared(struct collapse_context *c, struct me= m_ops *ops) { + struct thp_settings settings =3D *thp_current_settings(); int max_ptes_shared =3D thp_read_num("khugepaged/max_ptes_shared"); int wstatus; void *p; @@ -1100,6 +1110,9 @@ static void collapse_max_ptes_shared(struct collapse_= context *c, struct mem_ops 1, ops, !c->enforce_pte_scan_limits); =20 if (c->enforce_pte_scan_limits) { + settings.hugepages[collapse_order].enabled =3D THP_MADVISE; + thp_push_settings(&settings); + ksft_print_msg("Trigger CoW on page %d of %d...", hpage_pmd_nr - max_ptes_shared, hpage_pmd_nr); ops->fault(p, 0, (hpage_pmd_nr - max_ptes_shared) * @@ -1111,6 +1124,8 @@ static void collapse_max_ptes_shared(struct collapse_= context *c, struct mem_ops =20 c->collapse("Collapse with max_ptes_shared PTEs shared", p, 1, ops, true); + + thp_pop_settings(); } =20 validate_memory(p, 0, hpage_pmd_size); --=20 2.43.0