1 // SPDX-License-Identifier: GPL-2.0-only
3 * Usage: to be run via nx_huge_page_test.sh, which does the necessary
4 * environment setup and teardown
6 * Copyright (C) 2022, Google LLC.
15 #include <test_util.h>
17 #include "processor.h"
20 #define HPAGE_GPA (4UL << 30) /* 4G prevents collision w/ slot 0 */
21 #define HPAGE_GVA HPAGE_GPA /* GVA is arbitrary, so use GPA. */
22 #define PAGES_PER_2MB_HUGE_PAGE 512
23 #define HPAGE_SLOT_NPAGES (3 * PAGES_PER_2MB_HUGE_PAGE)
26 * Passed by nx_huge_pages_test.sh to provide an easy warning if this test is
27 * being run without it.
29 #define MAGIC_TOKEN 887563923
32 * x86 opcode for the return instruction. Used to call into, and then
33 * immediately return from, memory backed with hugepages.
35 #define RETURN_OPCODE 0xC3
37 /* Call the specified memory address. */
38 static void guest_do_CALL(uint64_t target)
40 ((void (*)(void)) target)();
44 * Exit the VM after each memory access so that the userspace component of the
45 * test can make assertions about the pages backing the VM.
47 * See the below for an explanation of how each access should affect the
52 uint64_t hpage_1 = HPAGE_GVA;
53 uint64_t hpage_2 = hpage_1 + (PAGE_SIZE * 512);
54 uint64_t hpage_3 = hpage_2 + (PAGE_SIZE * 512);
56 READ_ONCE(*(uint64_t *)hpage_1);
59 READ_ONCE(*(uint64_t *)hpage_2);
62 guest_do_CALL(hpage_1);
65 guest_do_CALL(hpage_3);
68 READ_ONCE(*(uint64_t *)hpage_1);
71 READ_ONCE(*(uint64_t *)hpage_3);
75 static void check_2m_page_count(struct kvm_vm *vm, int expected_pages_2m)
79 actual_pages_2m = vm_get_stat(vm, "pages_2m");
81 TEST_ASSERT(actual_pages_2m == expected_pages_2m,
82 "Unexpected 2m page count. Expected %d, got %d",
83 expected_pages_2m, actual_pages_2m);
86 static void check_split_count(struct kvm_vm *vm, int expected_splits)
90 actual_splits = vm_get_stat(vm, "nx_lpage_splits");
92 TEST_ASSERT(actual_splits == expected_splits,
93 "Unexpected NX huge page split count. Expected %d, got %d",
94 expected_splits, actual_splits);
97 static void wait_for_reclaim(int reclaim_period_ms)
102 reclaim_wait_ms = reclaim_period_ms * 5;
103 ts.tv_sec = reclaim_wait_ms / 1000;
104 ts.tv_nsec = (reclaim_wait_ms - (ts.tv_sec * 1000)) * 1000000;
105 nanosleep(&ts, NULL);
108 void run_test(int reclaim_period_ms, bool disable_nx_huge_pages,
109 bool reboot_permissions)
111 struct kvm_vcpu *vcpu;
119 if (disable_nx_huge_pages) {
120 r = __vm_disable_nx_huge_pages(vm);
121 if (reboot_permissions) {
122 TEST_ASSERT(!r, "Disabling NX huge pages should succeed if process has reboot permissions");
124 TEST_ASSERT(r == -1 && errno == EPERM,
125 "This process should not have permission to disable NX huge pages");
130 vcpu = vm_vcpu_add(vm, 0, guest_code);
132 vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS_HUGETLB,
133 HPAGE_GPA, HPAGE_SLOT,
134 HPAGE_SLOT_NPAGES, 0);
136 nr_bytes = HPAGE_SLOT_NPAGES * vm->page_size;
139 * Ensure that KVM can map HPAGE_SLOT with huge pages by mapping the
140 * region into the guest with 2MiB pages whenever TDP is disabled (i.e.
141 * whenever KVM is shadowing the guest page tables).
143 * When TDP is enabled, KVM should be able to map HPAGE_SLOT with huge
144 * pages irrespective of the guest page size, so map with 4KiB pages
145 * to test that that is the case.
147 if (kvm_is_tdp_enabled())
148 virt_map_level(vm, HPAGE_GVA, HPAGE_GPA, nr_bytes, PG_LEVEL_4K);
150 virt_map_level(vm, HPAGE_GVA, HPAGE_GPA, nr_bytes, PG_LEVEL_2M);
152 hva = addr_gpa2hva(vm, HPAGE_GPA);
153 memset(hva, RETURN_OPCODE, nr_bytes);
155 check_2m_page_count(vm, 0);
156 check_split_count(vm, 0);
159 * The guest code will first read from the first hugepage, resulting
160 * in a huge page mapping being created.
163 check_2m_page_count(vm, 1);
164 check_split_count(vm, 0);
167 * Then the guest code will read from the second hugepage, resulting
168 * in another huge page mapping being created.
171 check_2m_page_count(vm, 2);
172 check_split_count(vm, 0);
175 * Next, the guest will execute from the first huge page, causing it
176 * to be remapped at 4k.
178 * If NX huge pages are disabled, this should have no effect.
181 check_2m_page_count(vm, disable_nx_huge_pages ? 2 : 1);
182 check_split_count(vm, disable_nx_huge_pages ? 0 : 1);
185 * Executing from the third huge page (previously unaccessed) will
186 * cause part to be mapped at 4k.
188 * If NX huge pages are disabled, it should be mapped at 2M.
191 check_2m_page_count(vm, disable_nx_huge_pages ? 3 : 1);
192 check_split_count(vm, disable_nx_huge_pages ? 0 : 2);
194 /* Reading from the first huge page again should have no effect. */
196 check_2m_page_count(vm, disable_nx_huge_pages ? 3 : 1);
197 check_split_count(vm, disable_nx_huge_pages ? 0 : 2);
199 /* Give recovery thread time to run. */
200 wait_for_reclaim(reclaim_period_ms);
203 * Now that the reclaimer has run, all the split pages should be gone.
205 * If NX huge pages are disabled, the relaimer will not run, so
206 * nothing should change from here on.
208 check_2m_page_count(vm, disable_nx_huge_pages ? 3 : 1);
209 check_split_count(vm, 0);
212 * The 4k mapping on hpage 3 should have been removed, so check that
213 * reading from it causes a huge page mapping to be installed.
216 check_2m_page_count(vm, disable_nx_huge_pages ? 3 : 2);
217 check_split_count(vm, 0);
222 static void help(char *name)
225 printf("usage: %s [-h] [-p period_ms] [-t token]\n", name);
227 printf(" -p: The NX reclaim period in milliseconds.\n");
228 printf(" -t: The magic token to indicate environment setup is done.\n");
229 printf(" -r: The test has reboot permissions and can disable NX huge pages.\n");
234 int main(int argc, char **argv)
236 int reclaim_period_ms = 0, token = 0, opt;
237 bool reboot_permissions = false;
239 while ((opt = getopt(argc, argv, "hp:t:r")) != -1) {
242 reclaim_period_ms = atoi_positive("Reclaim period", optarg);
245 token = atoi_paranoid(optarg);
248 reboot_permissions = true;
257 TEST_REQUIRE(kvm_has_cap(KVM_CAP_VM_DISABLE_NX_HUGE_PAGES));
259 __TEST_REQUIRE(token == MAGIC_TOKEN,
260 "This test must be run with the magic token %d.\n"
261 "This is done by nx_huge_pages_test.sh, which\n"
262 "also handles environment setup for the test.");
264 run_test(reclaim_period_ms, false, reboot_permissions);
265 run_test(reclaim_period_ms, true, reboot_permissions);