From: "Kiryl Shutsemau (Meta)" <[email protected]> The upcoming khugepaged mTHP tests detect collapse results with the vm_util folio-order helpers instead of smaps AnonHugePages, which only sees PMD mappings. Before any collapse test trusts those helpers, make sure they agree with the kernel about what backs a mapping.
For every anon THP order the kernel supports, fault memory in with only that order enabled and require the helpers to classify the backing as exactly that order: not a neighbouring order, and 4K-backed memory as order 0. Runs in the thp category of run_vmtests.sh. Verified on x86-64 4K (orders 0, 2-9) and arm64 64K (orders 0, 2-13). Assisted-by: Claude-Code:claude-opus-5 Signed-off-by: Kiryl Shutsemau (Meta) <[email protected]> --- tools/testing/selftests/mm/.gitignore | 1 + tools/testing/selftests/mm/Makefile | 1 + .../testing/selftests/mm/folio_order_check.c | 138 ++++++++++++++++++ tools/testing/selftests/mm/run_vmtests.sh | 2 + 4 files changed, 142 insertions(+) create mode 100644 tools/testing/selftests/mm/folio_order_check.c diff --git a/tools/testing/selftests/mm/.gitignore b/tools/testing/selftests/mm/.gitignore index 9ccd9e1447e6..54eefd8f97bc 100644 --- a/tools/testing/selftests/mm/.gitignore +++ b/tools/testing/selftests/mm/.gitignore @@ -66,3 +66,4 @@ merge prctl_thp_disable rmap folio_split_race_test +folio_order_check diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile index 25d10ced3b3b..33917c76b871 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..f70d766ff3eb --- /dev/null +++ b/tools/testing/selftests/mm/folio_order_check.c @@ -0,0 +1,138 @@ +// 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 = ((uintptr_t)p + size - 1) & ~(size - 1); + 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); + } + + thp_restore_settings(); + + ksft_finished(); +} diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh index 687d115e3bd8..8bf898b71350 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 -- 2.54.0
