Add a test for page splitting during dirty logging and for hugepage
recovery after dirty logging.
Page splitting represents non-trivial behavior, which is complicated
by MANUAL_PROTECT mode, which causes pages to be split on the first
clear, instead of when dirty logging is enabled.
Add a test which makes asserions about page counts to help define the
expected behavior of page splitting and to provid needed coverage of the
behavior. This also helps ensure that a failure in eager page splitting
is not covered up by splitting in the vCPU path.
Tested by running the test on an Intel Haswell machine w/wo
MANUAL_PROTECT.
Signed-off-by: Ben Gardon <bgardon@xxxxxxxxxx>
---
tools/testing/selftests/kvm/Makefile | 1 +
.../selftests/kvm/include/kvm_util_base.h | 1 +
.../kvm/x86_64/page_splitting_test.c | 311 ++++++++++++++++++
3 files changed, 313 insertions(+)
create mode 100644 tools/testing/selftests/kvm/x86_64/page_splitting_test.c
diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index 1750f91dd9362..057ebd709e77a 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -76,6 +76,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/kvm_pv_test
TEST_GEN_PROGS_x86_64 += x86_64/mmio_warning_test
TEST_GEN_PROGS_x86_64 += x86_64/monitor_mwait_test
TEST_GEN_PROGS_x86_64 += x86_64/nested_exceptions_test
+TEST_GEN_PROGS_x86_64 += x86_64/page_splitting_test
TEST_GEN_PROGS_x86_64 += x86_64/platform_info_test
TEST_GEN_PROGS_x86_64 += x86_64/pmu_event_filter_test
TEST_GEN_PROGS_x86_64 += x86_64/set_boot_cpu_id
diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
index fbc2a79369b8b..98974a601b0af 100644
--- a/tools/testing/selftests/kvm/include/kvm_util_base.h
+++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
@@ -402,6 +402,7 @@ static inline uint64_t vm_get_stat(struct kvm_vm *vm, const char *stat_name)
uint64_t data;
__vm_get_stat(vm, stat_name, &data, 1);
+
return data;
}
diff --git a/tools/testing/selftests/kvm/x86_64/page_splitting_test.c b/tools/testing/selftests/kvm/x86_64/page_splitting_test.c
new file mode 100644
index 0000000000000..4b5dcd4908b5a
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86_64/page_splitting_test.c
@@ -0,0 +1,311 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KVM dirty logging page splitting test
+ *
+ * Based on dirty_log_perf.c
+ *
+ * Copyright (C) 2018, Red Hat, Inc.
+ * Copyright (C) 2020, Google, Inc.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <pthread.h>
+#include <linux/bitmap.h>
+
+#include "kvm_util.h"
+#include "test_util.h"
+#include "memstress.h"
+#include "guest_modes.h"
+
+/* How many host loops to run by default (one KVM_GET_DIRTY_LOG for each loop)*/
+#define TEST_HOST_LOOP_N 2UL
+
+static int NR_VCPUS = 2;
+static int NR_SLOTS = 2;
+static int NR_ITERATIONS = 2;
+static uint64_t guest_percpu_mem_size = DEFAULT_PER_VCPU_MEM_SIZE;
+
+/* Host variables */
+static u64 dirty_log_manual_caps;
+static bool host_quit;
+static int iteration;
+static int vcpu_last_completed_iteration[KVM_MAX_VCPUS];
+
+struct kvm_page_stats {
+ uint64_t pages_4k;
+ uint64_t pages_2m;
+ uint64_t pages_1g;
+ uint64_t hugepages;
+};
+
+static void get_page_stats(struct kvm_vm *vm, struct kvm_page_stats *stats)
+{
+ stats->pages_4k = vm_get_stat(vm, "pages_4k");
+ stats->pages_2m = vm_get_stat(vm, "pages_2m");
+ stats->pages_1g = vm_get_stat(vm, "pages_1g");
+ stats->hugepages = stats->pages_2m + stats->pages_1g;
+
+ pr_debug("Page stats - 4K: %ld 2M: %ld 1G: %ld huge: %ld\n",
+ stats->pages_4k, stats->pages_2m, stats->pages_1g,
+ stats->hugepages);
+}
+
+static void vcpu_worker(struct memstress_vcpu_args *vcpu_args)
+{
+ struct kvm_vcpu *vcpu = vcpu_args->vcpu;
+ int vcpu_idx = vcpu_args->vcpu_idx;
+ uint64_t pages_count = 0;
+ struct kvm_run *run;
+ int ret;
+
+ run = vcpu->run;
+
+ while (!READ_ONCE(host_quit)) {
+ int current_iteration = READ_ONCE(iteration);
+
+ ret = _vcpu_run(vcpu);
+
+ TEST_ASSERT(ret == 0, "vcpu_run failed: %d\n", ret);
+ TEST_ASSERT(get_ucall(vcpu, NULL) == UCALL_SYNC,
+ "Invalid guest sync status: exit_reason=%s\n",
+ exit_reason_str(run->exit_reason));
+
+ vcpu_last_completed_iteration[vcpu_idx] = current_iteration;
+
+ if (current_iteration)
+ pages_count += vcpu_args->pages;
+
+ /* Wait for the start of the next iteration to be signaled. */
+ while (current_iteration == READ_ONCE(iteration) &&
+ READ_ONCE(iteration) >= 0 &&
+ !READ_ONCE(host_quit))
+ ;
+ }
+}
+
+struct test_params {
+ enum vm_mem_backing_src_type backing_src;
+};
+
+static void run_test(struct test_params *p)
+{
+ struct kvm_vm *vm;
+ unsigned long **bitmaps;
+ uint64_t guest_num_pages;
+ uint64_t host_num_pages;
+ uint64_t pages_per_slot;
+ int i;
+ uint64_t total_4k_pages;
+ struct kvm_page_stats stats_populated;
+ struct kvm_page_stats stats_dirty_logging_enabled;
+ struct kvm_page_stats stats_dirty_pass[NR_ITERATIONS];
+ struct kvm_page_stats stats_clear_pass[NR_ITERATIONS];
+ struct kvm_page_stats stats_dirty_logging_disabled;
+ struct kvm_page_stats stats_repopulated;
+
+ vm = memstress_create_vm(VM_MODE_DEFAULT, NR_VCPUS, guest_percpu_mem_size,
+ NR_SLOTS, p->backing_src, false);
+
+ guest_num_pages = (NR_VCPUS * guest_percpu_mem_size) >> vm->page_shift;
+ guest_num_pages = vm_adjust_num_guest_pages(VM_MODE_DEFAULT, guest_num_pages);
+ host_num_pages = vm_num_host_pages(VM_MODE_DEFAULT, guest_num_pages);
+ pages_per_slot = host_num_pages / NR_SLOTS;
+
+ bitmaps = memstress_alloc_bitmaps(NR_SLOTS, pages_per_slot);
+
+ if (dirty_log_manual_caps)
+ vm_enable_cap(vm, KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2,
+ dirty_log_manual_caps);
+
+ /* Start the iterations */
+ iteration = 0;
+ host_quit = false;
+
+ for (i = 0; i < NR_VCPUS; i++)
+ vcpu_last_completed_iteration[i] = -1;
+
+ memstress_start_vcpu_threads(NR_VCPUS, vcpu_worker);
+
+ /* Allow the vCPUs to populate memory */
+ for (i = 0; i < NR_VCPUS; i++) {
+ while (READ_ONCE(vcpu_last_completed_iteration[i]) !=
+ iteration)
+ ;
+ }
+
+ pr_debug("\nGetting stats after populating memory:\n");
+ get_page_stats(vm, &stats_populated);
+
+ /* Enable dirty logging */
+ memstress_enable_dirty_logging(vm, NR_SLOTS);
+
+ pr_debug("\nGetting stats after enabling dirty logging:\n");
+ get_page_stats(vm, &stats_dirty_logging_enabled);
+
+ while (iteration < NR_ITERATIONS) {
+ /*
+ * Incrementing the iteration number will start the vCPUs
+ * dirtying memory again.
+ */
+ iteration++;
+
+ for (i = 0; i < NR_VCPUS; i++) {
+ while (READ_ONCE(vcpu_last_completed_iteration[i])
+ != iteration)
+ ;
+ }
+
+ pr_debug("\nGetting stats after dirtying memory on pass %d:\n", iteration);
+ get_page_stats(vm, &stats_dirty_pass[iteration - 1]);
+
+ memstress_get_dirty_log(vm, bitmaps, NR_SLOTS);
+
+ if (dirty_log_manual_caps) {
+ memstress_clear_dirty_log(vm, bitmaps, NR_SLOTS, pages_per_slot);
+
+ pr_debug("\nGetting stats after clearing dirty log pass %d:\n", iteration);
+ get_page_stats(vm, &stats_clear_pass[iteration - 1]);
+ }
+ }
+
+ /* Disable dirty logging */
+ memstress_disable_dirty_logging(vm, NR_SLOTS);
+
+ pr_debug("\nGetting stats after disabling dirty logging:\n");
+ get_page_stats(vm, &stats_dirty_logging_disabled);
+
+ /* Run vCPUs again to fault pages back in. */
+ iteration++;
+ for (i = 0; i < NR_VCPUS; i++) {
+ while (READ_ONCE(vcpu_last_completed_iteration[i]) != iteration)
+ ;
+ }
+
+ pr_debug("\nGetting stats after repopulating memory:\n");
+ get_page_stats(vm, &stats_repopulated);
+
+ /*
+ * Tell the vCPU threads to quit. No need to manually check that vCPUs
+ * have stopped running after disabling dirty logging, the join will
+ * wait for them to exit.
+ */
+ host_quit = true;
+ memstress_join_vcpu_threads(NR_VCPUS);
+
+ memstress_free_bitmaps(bitmaps, NR_SLOTS);
+ memstress_destroy_vm(vm);
+
+ /* Make assertions about the page counts. */
+ total_4k_pages = stats_populated.pages_4k;
+ total_4k_pages += stats_populated.pages_2m * 512;
+ total_4k_pages += stats_populated.pages_1g * 512 * 512;
+
+ /*
+ * Check that all huge pages were split. Since large pages can only
+ * exist in the data slot, and the vCPUs should have dirtied all pages
+ * in the data slot, there should be no huge pages left after splitting.
+ * Splitting happens at dirty log enable time without
+ * KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 and after the first clear pass
+ * with that capability.
+ */
+ if (dirty_log_manual_caps) {
+ TEST_ASSERT(stats_clear_pass[0].hugepages == 0,
+ "Unexpected huge page count after splitting. Expected 0, got %ld",
+ stats_clear_pass[0].hugepages);
+ TEST_ASSERT(stats_clear_pass[0].pages_4k == total_4k_pages,
+ "All memory should be mapped at 4k. Expected %ld 4k pages, got %ld",
+ total_4k_pages, stats_clear_pass[0].pages_4k);
+ } else {
+ TEST_ASSERT(stats_dirty_logging_enabled.hugepages == 0,
+ "Unexpected huge page count after splitting. Expected 0, got %ld",
+ stats_dirty_logging_enabled.hugepages);
+ TEST_ASSERT(stats_dirty_logging_enabled.pages_4k == total_4k_pages,
+ "All memory should be mapped at 4k. Expected %ld 4k pages, got %ld",
+ total_4k_pages, stats_dirty_logging_enabled.pages_4k);
+ }
+
+ /*
+ * Once dirty logging is disabled and the vCPUs have touched all their
+ * memory again, the page counts should be the same as they were
+ * right after initial population of memory.
+ */
+ TEST_ASSERT(stats_populated.pages_4k == stats_repopulated.pages_4k,
+ "4k page count did not return to its initial value after "
+ "dirty logging. Expected %ld, got %ld",
+ stats_populated.pages_4k, stats_repopulated.pages_4k);
+ TEST_ASSERT(stats_populated.pages_2m == stats_repopulated.pages_2m,
+ "2m page count did not return to its initial value after "
+ "dirty logging. Expected %ld, got %ld",
+ stats_populated.pages_2m, stats_repopulated.pages_2m);
+ TEST_ASSERT(stats_populated.pages_1g == stats_repopulated.pages_1g,
+ "1g page count did not return to its initial value after "
+ "dirty logging. Expected %ld, got %ld",
+ stats_populated.pages_1g, stats_repopulated.pages_1g);
+}
+
+static void help(char *name)
+{
+ puts("");
+ printf("usage: %s [-h] [-g] [-m mode] [-b vcpu bytes] [-s mem type]\n",
+ name);
+ puts("");
+ printf(" -g: Do not enable KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2. This\n"
+ " makes KVM_GET_DIRTY_LOG clear the dirty log (i.e.\n"
+ " KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE is not enabled)\n"
+ " and writes will be tracked as soon as dirty logging is\n"
+ " enabled on the memslot (i.e. KVM_DIRTY_LOG_INITIALLY_SET\n"
+ " is not enabled).\n");
+ printf(" -b: specify the size of the memory region which should be\n"
+ " dirtied by each vCPU. e.g. 10M or 3G.\n"
+ " (default: 1G)\n");
+ backing_src_help("-s");
+ puts("");
+ exit(0);
+}
+
+int main(int argc, char *argv[])
+{
+ struct test_params p = {
+ .backing_src = VM_MEM_SRC_ANONYMOUS_HUGETLB,
+ };
+ int opt;
+
+ dirty_log_manual_caps =
+ kvm_check_cap(KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2);
+ dirty_log_manual_caps &= (KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE |
+ KVM_DIRTY_LOG_INITIALLY_SET);
+
+ guest_modes_append_default();
+
+ while ((opt = getopt(argc, argv, "b:ghs:")) != -1) {
+ switch (opt) {
+ case 'b':
+ guest_percpu_mem_size = parse_size(optarg);
+ break;
+ case 'g':
+ dirty_log_manual_caps = 0;
+ break;
+ case 'h':
+ help(argv[0]);
+ break;
+ case 's':
+ p.backing_src = parse_backing_src_type(optarg);
+ break;
+ default:
+ help(argv[0]);
+ break;
+ }
+ }
+
+ if (!is_backing_src_hugetlb(p.backing_src)) {
+ pr_info("This test will only work reliably with HugeTLB memory. "
+ "It can work with THP, but that is best effort.");
+ return KSFT_SKIP;
+ }
+
+ run_test(&p);
+
+ return 0;
+}
--
2.39.1.405.gd4c25cc71f-goog
