On Sat, Aug 15, 2026 at 02:58:51AM +0100, Kiryl Shutsemau wrote: > From: "Kiryl Shutsemau (Meta)" <[email protected]> > > 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 <[email protected]> > Signed-off-by: Kiryl Shutsemau (Meta) <[email protected]> > --- > 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 <fcntl.h> > +#include <stdio.h> > +#include <stdlib.h> > +#include <sys/mman.h> > +#include <unistd.h> > + > +#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 <linux/fs.h> > > #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
