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Diffstat (limited to '')
-rw-r--r-- | tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.c | 269 |
1 files changed, 269 insertions, 0 deletions
diff --git a/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.c b/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.c new file mode 100644 index 000000000000..17bbb96fc4df --- /dev/null +++ b/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.c @@ -0,0 +1,269 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Usage: to be run via nx_huge_page_test.sh, which does the necessary + * environment setup and teardown + * + * Copyright (C) 2022, Google LLC. + */ + +#define _GNU_SOURCE + +#include <fcntl.h> +#include <stdint.h> +#include <time.h> + +#include <test_util.h> +#include "kvm_util.h" +#include "processor.h" + +#define HPAGE_SLOT 10 +#define HPAGE_GPA (4UL << 30) /* 4G prevents collision w/ slot 0 */ +#define HPAGE_GVA HPAGE_GPA /* GVA is arbitrary, so use GPA. */ +#define PAGES_PER_2MB_HUGE_PAGE 512 +#define HPAGE_SLOT_NPAGES (3 * PAGES_PER_2MB_HUGE_PAGE) + +/* + * Passed by nx_huge_pages_test.sh to provide an easy warning if this test is + * being run without it. + */ +#define MAGIC_TOKEN 887563923 + +/* + * x86 opcode for the return instruction. Used to call into, and then + * immediately return from, memory backed with hugepages. + */ +#define RETURN_OPCODE 0xC3 + +/* Call the specified memory address. */ +static void guest_do_CALL(uint64_t target) +{ + ((void (*)(void)) target)(); +} + +/* + * Exit the VM after each memory access so that the userspace component of the + * test can make assertions about the pages backing the VM. + * + * See the below for an explanation of how each access should affect the + * backing mappings. + */ +void guest_code(void) +{ + uint64_t hpage_1 = HPAGE_GVA; + uint64_t hpage_2 = hpage_1 + (PAGE_SIZE * 512); + uint64_t hpage_3 = hpage_2 + (PAGE_SIZE * 512); + + READ_ONCE(*(uint64_t *)hpage_1); + GUEST_SYNC(1); + + READ_ONCE(*(uint64_t *)hpage_2); + GUEST_SYNC(2); + + guest_do_CALL(hpage_1); + GUEST_SYNC(3); + + guest_do_CALL(hpage_3); + GUEST_SYNC(4); + + READ_ONCE(*(uint64_t *)hpage_1); + GUEST_SYNC(5); + + READ_ONCE(*(uint64_t *)hpage_3); + GUEST_SYNC(6); +} + +static void check_2m_page_count(struct kvm_vm *vm, int expected_pages_2m) +{ + int actual_pages_2m; + + actual_pages_2m = vm_get_stat(vm, "pages_2m"); + + TEST_ASSERT(actual_pages_2m == expected_pages_2m, + "Unexpected 2m page count. Expected %d, got %d", + expected_pages_2m, actual_pages_2m); +} + +static void check_split_count(struct kvm_vm *vm, int expected_splits) +{ + int actual_splits; + + actual_splits = vm_get_stat(vm, "nx_lpage_splits"); + + TEST_ASSERT(actual_splits == expected_splits, + "Unexpected NX huge page split count. Expected %d, got %d", + expected_splits, actual_splits); +} + +static void wait_for_reclaim(int reclaim_period_ms) +{ + long reclaim_wait_ms; + struct timespec ts; + + reclaim_wait_ms = reclaim_period_ms * 5; + ts.tv_sec = reclaim_wait_ms / 1000; + ts.tv_nsec = (reclaim_wait_ms - (ts.tv_sec * 1000)) * 1000000; + nanosleep(&ts, NULL); +} + +void run_test(int reclaim_period_ms, bool disable_nx_huge_pages, + bool reboot_permissions) +{ + struct kvm_vcpu *vcpu; + struct kvm_vm *vm; + uint64_t nr_bytes; + void *hva; + int r; + + vm = vm_create(1); + + if (disable_nx_huge_pages) { + r = __vm_disable_nx_huge_pages(vm); + if (reboot_permissions) { + TEST_ASSERT(!r, "Disabling NX huge pages should succeed if process has reboot permissions"); + } else { + TEST_ASSERT(r == -1 && errno == EPERM, + "This process should not have permission to disable NX huge pages"); + return; + } + } + + vcpu = vm_vcpu_add(vm, 0, guest_code); + + vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS_HUGETLB, + HPAGE_GPA, HPAGE_SLOT, + HPAGE_SLOT_NPAGES, 0); + + nr_bytes = HPAGE_SLOT_NPAGES * vm->page_size; + + /* + * Ensure that KVM can map HPAGE_SLOT with huge pages by mapping the + * region into the guest with 2MiB pages whenever TDP is disabled (i.e. + * whenever KVM is shadowing the guest page tables). + * + * When TDP is enabled, KVM should be able to map HPAGE_SLOT with huge + * pages irrespective of the guest page size, so map with 4KiB pages + * to test that that is the case. + */ + if (kvm_is_tdp_enabled()) + virt_map_level(vm, HPAGE_GVA, HPAGE_GPA, nr_bytes, PG_LEVEL_4K); + else + virt_map_level(vm, HPAGE_GVA, HPAGE_GPA, nr_bytes, PG_LEVEL_2M); + + hva = addr_gpa2hva(vm, HPAGE_GPA); + memset(hva, RETURN_OPCODE, nr_bytes); + + check_2m_page_count(vm, 0); + check_split_count(vm, 0); + + /* + * The guest code will first read from the first hugepage, resulting + * in a huge page mapping being created. + */ + vcpu_run(vcpu); + check_2m_page_count(vm, 1); + check_split_count(vm, 0); + + /* + * Then the guest code will read from the second hugepage, resulting + * in another huge page mapping being created. + */ + vcpu_run(vcpu); + check_2m_page_count(vm, 2); + check_split_count(vm, 0); + + /* + * Next, the guest will execute from the first huge page, causing it + * to be remapped at 4k. + * + * If NX huge pages are disabled, this should have no effect. + */ + vcpu_run(vcpu); + check_2m_page_count(vm, disable_nx_huge_pages ? 2 : 1); + check_split_count(vm, disable_nx_huge_pages ? 0 : 1); + + /* + * Executing from the third huge page (previously unaccessed) will + * cause part to be mapped at 4k. + * + * If NX huge pages are disabled, it should be mapped at 2M. + */ + vcpu_run(vcpu); + check_2m_page_count(vm, disable_nx_huge_pages ? 3 : 1); + check_split_count(vm, disable_nx_huge_pages ? 0 : 2); + + /* Reading from the first huge page again should have no effect. */ + vcpu_run(vcpu); + check_2m_page_count(vm, disable_nx_huge_pages ? 3 : 1); + check_split_count(vm, disable_nx_huge_pages ? 0 : 2); + + /* Give recovery thread time to run. */ + wait_for_reclaim(reclaim_period_ms); + + /* + * Now that the reclaimer has run, all the split pages should be gone. + * + * If NX huge pages are disabled, the relaimer will not run, so + * nothing should change from here on. + */ + check_2m_page_count(vm, disable_nx_huge_pages ? 3 : 1); + check_split_count(vm, 0); + + /* + * The 4k mapping on hpage 3 should have been removed, so check that + * reading from it causes a huge page mapping to be installed. + */ + vcpu_run(vcpu); + check_2m_page_count(vm, disable_nx_huge_pages ? 3 : 2); + check_split_count(vm, 0); + + kvm_vm_free(vm); +} + +static void help(char *name) +{ + puts(""); + printf("usage: %s [-h] [-p period_ms] [-t token]\n", name); + puts(""); + printf(" -p: The NX reclaim period in milliseconds.\n"); + printf(" -t: The magic token to indicate environment setup is done.\n"); + printf(" -r: The test has reboot permissions and can disable NX huge pages.\n"); + puts(""); + exit(0); +} + +int main(int argc, char **argv) +{ + int reclaim_period_ms = 0, token = 0, opt; + bool reboot_permissions = false; + + while ((opt = getopt(argc, argv, "hp:t:r")) != -1) { + switch (opt) { + case 'p': + reclaim_period_ms = atoi_positive("Reclaim period", optarg); + break; + case 't': + token = atoi_paranoid(optarg); + break; + case 'r': + reboot_permissions = true; + break; + case 'h': + default: + help(argv[0]); + break; + } + } + + TEST_REQUIRE(kvm_has_cap(KVM_CAP_VM_DISABLE_NX_HUGE_PAGES)); + + __TEST_REQUIRE(token == MAGIC_TOKEN, + "This test must be run with the magic token via '-t %d'.\n" + "Running via nx_huge_pages_test.sh, which also handles " + "environment setup, is strongly recommended.", MAGIC_TOKEN); + + run_test(reclaim_period_ms, false, reboot_permissions); + run_test(reclaim_period_ms, true, reboot_permissions); + + return 0; +} + |