From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 45BB644C670; Tue, 18 Aug 2026 10:30:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787049029; cv=none; b=D4YU6x5PcxsdbAg+9ncmRypwoJzkGwIJwLlnjJMTitqXjaL9gRGsUwtFO9rT717OXPLVZpqd44pVgpCiExYrDRZCJxzq9ReSO79f3qPpvyUWBKDSXkhQkD2VSymIaylyAiz/UFZY2TrYsC+CiZh0w0e2z98N/HQ+aLlobVbT4Ns= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787049029; c=relaxed/simple; bh=KkYrt4eBsmmtGpMK/EFXNxyETR7F3WVA7tg4vzsroUU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=nY/ccG9gIZeHJxdZTDFv80kK04W/eRw5rXA2DkAwse3NcYj2IPPsGTf1RJva4ENJt4cNO0X/b5wrCE4INj+NOi/Y9uoa7W/KqnFTE3LeruEN0Rlc5X21muND0qyqpLCc0bWMKpwEXzYnjVw8LJM3P3JJPJWn5SajR9OHOqOYMsk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=nXOALRLg; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="nXOALRLg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9253E1F000E9; Tue, 18 Aug 2026 10:30:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787049027; bh=gFhmJcPos1AhWRORhzMLbjRopLVZZ4MU49Dk+N+uRMo=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=nXOALRLgudDLqMVtGF70wtuuATsP+Nharszx6noAKLgW3XYTxcxa0XvnkPU/m+TD8 vxGbfu0VLrD3QqjzylKJQoL6l5+Bx0Qhgs81NGBfWJCFPxHpHaFg4ooT6oM/C2H0+5 qRTOZSyUx4JSta/8RFiDr0s87NbQ0+0j4JrfV08Zn8gnvqQoRqyasmSpFD9e9jTfoX TJqOYu+TmoxfLLQHzIU4hdTnw2cus6N9Y5UF1Hz5f5EG8K6Pw9h3GbdHkW9H10rAnJ CgixQGAhJnAloRIgZvyvjvx9n9wmJrKmiG2QbzI5SzriixPtalSG2P0girqkO6+wDm UG0jwJd3tEeeA== Date: Tue, 18 Aug 2026 11:30:06 +0100 From: "Lorenzo Stoakes (ARM)" To: Kiryl Shutsemau Cc: akpm@linux-foundation.org, david@kernel.org, nico.pache@linux.dev, baolin.wang@linux.alibaba.com, baohua@kernel.org, dev.jain@arm.com, hughd@google.com, lance.yang@linux.dev, liam@infradead.org, mhocko@suse.com, rppt@kernel.org, ryan.roberts@arm.com, shuah@kernel.org, surenb@google.com, usama.arif@linux.dev, vbabka@kernel.org, ziy@nvidia.com, usama.anjum@arm.com, agordeev@linux.ibm.com, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, kas@kernel.org Subject: Re: [PATCH v4 09/19] selftests/mm: add folio-order detection self-check Message-ID: References: <20260815015901.1236937-1-kirill@shutemov.name> <20260815015901.1236937-10-kirill@shutemov.name> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260815015901.1236937-10-kirill@shutemov.name> On Sat, Aug 15, 2026 at 02:58:51AM +0100, Kiryl Shutsemau wrote: > From: "Kiryl Shutsemau (Meta)" > > The khugepaged mTHP tests detect collapse results with the vm_util > folio-order helpers rather than smaps AnonHugePages, which only sees PMD > mappings. If those helpers are wrong, every case built on them is wrong > the same way, and nothing says so. > > Check them directly. For every anon THP order the kernel supports, fault > memory in with only that order enabled. Require the helpers to classify > the backing as exactly that order: not a neighbouring order, and 4K-backed > memory as order 0. > > Run it in the thp category, ahead of ./khugepaged, so a broken helper is > reported as itself rather than as a collapse failure. Verified on x86-64 > 4K (orders 0, 2-9) and arm64 64K (orders 0, 2-13). > > The test needs ALIGN(), which hmm-tests.c and migration.c each defined > privately. Move it to vm_util.h and drop both copies. Also: uffd-unit-tests defines ALIGN_UP()... And really you probably want to match the kernel convention of ALIGN() defaulting to align-up (for some reason) and name this ALIGN_DOWN() to be consistent and avoid confusion BUT... Since the tests already do this mistake I guess it's not so bad to share the define and propagate it for now I suppose. > > Assisted-by: Claude-Code:claude-opus-5 > Tested-by: Muhammad Usama Anjum > Signed-off-by: Kiryl Shutsemau (Meta) > --- > tools/testing/selftests/mm/Makefile | 1 + > .../testing/selftests/mm/folio_order_check.c | 137 ++++++++++++++++++ > tools/testing/selftests/mm/hmm-tests.c | 1 - > tools/testing/selftests/mm/migration.c | 1 - > tools/testing/selftests/mm/run_vmtests.sh | 2 + > tools/testing/selftests/mm/vm_util.h | 2 + > 6 files changed, 142 insertions(+), 2 deletions(-) > create mode 100644 tools/testing/selftests/mm/folio_order_check.c > > diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile > index 2d5366196e30..2093fcf6e915 100644 > --- a/tools/testing/selftests/mm/Makefile > +++ b/tools/testing/selftests/mm/Makefile > @@ -104,6 +104,7 @@ TEST_GEN_FILES += guard-regions > TEST_GEN_FILES += merge > TEST_GEN_FILES += rmap > TEST_GEN_FILES += folio_split_race_test > +TEST_GEN_FILES += folio_order_check > > ifneq ($(ARCH),arm64) > TEST_GEN_FILES += soft-dirty > diff --git a/tools/testing/selftests/mm/folio_order_check.c b/tools/testing/selftests/mm/folio_order_check.c > new file mode 100644 > index 000000000000..93030a42c3cc > --- /dev/null > +++ b/tools/testing/selftests/mm/folio_order_check.c > @@ -0,0 +1,137 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Self-check for the vm_util folio-order detection helpers, > + * is_backed_by_folio() and is_range_backed_by_folio_orders(). > + * > + * For every anon THP order the kernel supports, fault memory in with only > + * that order enabled and verify the helpers report exactly that order: > + * not a neighbouring order, and plain 4K memory as order 0. The helpers > + * are what the khugepaged mTHP tests use to detect collapse results, so > + * they must agree with the kernel's own idea of the backing before any > + * collapse test relies on them. > + */ > +#define _GNU_SOURCE > +#include > +#include > +#include > +#include > +#include > + > +#include "kselftest.h" > +#include "vm_util.h" > +#include "hugepage_settings.h" > + > +static int pagemap_fd; > +static int kpageflags_fd; > + > +/* mmap an anon VMA of exactly @size bytes at a @size-aligned address. */ > +static char *alloc_aligned(size_t size) > +{ > + size_t len = size * 2; > + uintptr_t aligned; > + char *p; > + > + p = mmap(NULL, len, PROT_READ | PROT_WRITE, > + MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); > + if (p == MAP_FAILED) > + ksft_exit_fail_perror("mmap()"); > + > + aligned = ALIGN((uintptr_t)p, size); > + if (aligned != (uintptr_t)p) > + munmap(p, aligned - (uintptr_t)p); > + if (aligned + size != (uintptr_t)p + len) > + munmap((char *)aligned + size, > + (uintptr_t)p + len - aligned - size); > + > + return (char *)aligned; > +} > + > +/* > + * Enable only @order (order 0: nothing), fault one aligned window in and > + * check the helpers see exactly @order. > + */ > +static void check_order(int order) > +{ > + struct thp_settings settings = *thp_current_settings(); > + size_t size = psize() << order; > + bool ok = true; > + char *p; > + int i; > + > + for (i = 0; i < NR_ORDERS; i++) > + settings.hugepages[i].enabled = THP_NEVER; > + if (order) > + settings.hugepages[order].enabled = THP_ALWAYS; > + thp_push_settings(&settings); > + > + p = alloc_aligned(size); > + *p = 1; > + > + if (!is_range_backed_by_folio_orders(p, size, order, > + pagemap_fd, kpageflags_fd)) { > + ksft_print_msg("order %d not detected after fault\n", order); > + ok = false; > + } > + > + /* A lower order must be rejected: the folio is larger. */ > + if (order && is_range_backed_by_folio_orders(p, size, order - 1, > + pagemap_fd, > + kpageflags_fd)) { > + ksft_print_msg("order %d also reported as order %d\n", > + order, order - 1); > + ok = false; > + } > + > + /* Order 0 pages must not look like any large folio, and vice versa. */ > + if (order && is_range_backed_by_folio_orders(p, size, 0, > + pagemap_fd, > + kpageflags_fd)) { > + ksft_print_msg("order %d also reported as order 0\n", order); > + ok = false; > + } > + > + munmap(p, size); > + thp_pop_settings(); > + > + ksft_test_result(ok, "order %d classified\n", order); > +} > + > +int main(void) > +{ > + struct thp_settings settings; > + unsigned long orders; > + int order; > + > + ksft_print_header(); > + > + if (!thp_available()) > + ksft_exit_skip("Transparent Hugepages not available\n"); > + > + pagemap_fd = open("/proc/self/pagemap", O_RDONLY); > + if (pagemap_fd < 0) > + ksft_exit_fail_perror("open(/proc/self/pagemap)"); > + kpageflags_fd = open("/proc/kpageflags", O_RDONLY); > + if (kpageflags_fd < 0) > + ksft_exit_skip("open(\"/proc/kpageflags\") requires root\n"); > + > + orders = thp_supported_orders(); > + if (!orders) > + ksft_exit_skip("No supported THP orders\n"); > + > + ksft_set_plan(__builtin_popcountl(orders) + 1); > + > + thp_save_settings(); > + thp_read_settings(&settings); > + /* Base of the settings stack; the bottom entry is never popped. */ > + thp_push_settings(&settings); > + > + check_order(0); > + for (order = 1; order < NR_ORDERS; order++) { > + if (!(orders & (1UL << order))) > + continue; > + check_order(order); > + } > + > + > + ksft_finished(); > +} > diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c > index e2642eca0d02..df426f9218e7 100644 > --- a/tools/testing/selftests/mm/hmm-tests.c > +++ b/tools/testing/selftests/mm/hmm-tests.c > @@ -65,7 +65,6 @@ enum { > #define HMM_PATH_MAX 64 > #define NTIMES 10 > > -#define ALIGN(x, a) (((x) + (a - 1)) & (~((a) - 1))) > /* Just the flags we need, copied from mm.h: */ > > #ifndef FOLL_WRITE > diff --git a/tools/testing/selftests/mm/migration.c b/tools/testing/selftests/mm/migration.c > index f19d53c69576..fd35f8a7b5b8 100644 > --- a/tools/testing/selftests/mm/migration.c > +++ b/tools/testing/selftests/mm/migration.c > @@ -20,7 +20,6 @@ > > #define TWOMEG (2<<20) > #define RUNTIME (20) > -#define ALIGN(x, a) (((x) + (a - 1)) & (~((a) - 1))) > > HUGETLB_SETUP_DEFAULT_PAGES(1) > > diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh > index d09f9f6a384e..2652a7920b80 100755 > --- a/tools/testing/selftests/mm/run_vmtests.sh > +++ b/tools/testing/selftests/mm/run_vmtests.sh > @@ -402,6 +402,8 @@ CATEGORY="pfnmap" run_test ./pfnmap > # COW tests > CATEGORY="cow" run_test ./cow > > +CATEGORY="thp" run_test ./folio_order_check > + > CATEGORY="thp" run_test ./khugepaged > > CATEGORY="thp" run_test ./khugepaged -s 2 > diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h > index 39dfb18dc10c..ce05bce4670d 100644 > --- a/tools/testing/selftests/mm/vm_util.h > +++ b/tools/testing/selftests/mm/vm_util.h > @@ -10,6 +10,8 @@ > #include > > #define BIT_ULL(nr) (1ULL << (nr)) > +#define ALIGN(x, a) (((x) + (a) - 1) & ~((a) - 1)) > + > #define PM_SOFT_DIRTY BIT_ULL(55) > #define PM_MMAP_EXCLUSIVE BIT_ULL(56) > #define PM_UFFD_WP BIT_ULL(57) > -- > 2.54.0 > -- Cheers, Lorenzo