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. 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
