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 assertions about page counts to help define the
expected behavior of page splitting and to provide 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.
Reviewed-by: Vipin Sharma <vipinsh@xxxxxxxxxx>
Signed-off-by: Ben Gardon <bgardon@xxxxxxxxxx>
---
tools/testing/selftests/kvm/Makefile | 1 +
.../selftests/kvm/include/kvm_util_base.h | 1 +
tools/testing/selftests/kvm/lib/kvm_util.c | 5 +
.../x86_64/dirty_log_page_splitting_test.c | 260 ++++++++++++++++++
4 files changed, 267 insertions(+)
create mode 100644 tools/testing/selftests/kvm/x86_64/dirty_log_page_splitting_test.c
diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index 1750f91dd9362..9a8022918c3ea 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -61,6 +61,7 @@ TEST_PROGS_x86_64 += x86_64/nx_huge_pages_test.sh
# Compiled test targets
TEST_GEN_PROGS_x86_64 = x86_64/cpuid_test
TEST_GEN_PROGS_x86_64 += x86_64/cr4_cpuid_sync_test
+TEST_GEN_PROGS_x86_64 += x86_64/dirty_log_page_splitting_test
TEST_GEN_PROGS_x86_64 += x86_64/get_msr_index_features
TEST_GEN_PROGS_x86_64 += x86_64/exit_on_emulation_failure_test
TEST_GEN_PROGS_x86_64 += x86_64/fix_hypercall_test
diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
index fbc2a79369b8b..a089c356f354e 100644
--- a/tools/testing/selftests/kvm/include/kvm_util_base.h
+++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
@@ -213,6 +213,7 @@ extern const struct vm_guest_mode_params vm_guest_mode_params[];
int open_path_or_exit(const char *path, int flags);
int open_kvm_dev_path_or_exit(void);
+bool get_kvm_param_bool(const char *param);
bool get_kvm_intel_param_bool(const char *param);
bool get_kvm_amd_param_bool(const char *param);
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 56d5ea949cbbe..fa6d69f731990 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -80,6 +80,11 @@ static bool get_module_param_bool(const char *module_name, const char *param)
TEST_FAIL("Unrecognized value '%c' for boolean module param", value);
}
+bool get_kvm_param_bool(const char *param)
+{
+ return get_module_param_bool("kvm", param);
+}
+
bool get_kvm_intel_param_bool(const char *param)
{
return get_module_param_bool("kvm_intel", param);
diff --git a/tools/testing/selftests/kvm/x86_64/dirty_log_page_splitting_test.c b/tools/testing/selftests/kvm/x86_64/dirty_log_page_splitting_test.c
new file mode 100644
index 0000000000000..ed08c7ac3b2e3
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86_64/dirty_log_page_splitting_test.c
@@ -0,0 +1,260 @@
+// 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) 2023, Google, Inc.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <linux/bitmap.h>
+
+#include "kvm_util.h"
+#include "test_util.h"
+#include "memstress.h"
+#include "guest_modes.h"
+
+#define VCPUS 2
+#define SLOTS 2
+#define ITERATIONS 2
+
+static uint64_t guest_percpu_mem_size = DEFAULT_PER_VCPU_MEM_SIZE;
+
+static enum vm_mem_backing_src_type backing_src = VM_MEM_SRC_ANONYMOUS_HUGETLB;
+
+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, const char *stage)
+{
+ 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("\nPage stats after %s: 4K: %ld 2M: %ld 1G: %ld huge: %ld\n",
+ stage, stats->pages_4k, stats->pages_2m, stats->pages_1g,
+ stats->hugepages);
+}
+
+static void run_vcpu_iteration(struct kvm_vm *vm)
+{
+ int i;
+
+ iteration++;
+ for (i = 0; i < VCPUS; i++) {
+ while (READ_ONCE(vcpu_last_completed_iteration[i]) !=
+ iteration)
+ ;
+ }
+}
+
+static void vcpu_worker(struct memstress_vcpu_args *vcpu_args)
+{
+ struct kvm_vcpu *vcpu = vcpu_args->vcpu;
+ int vcpu_idx = vcpu_args->vcpu_idx;
+
+ while (!READ_ONCE(host_quit)) {
+ int current_iteration = READ_ONCE(iteration);
+
+ vcpu_run(vcpu);
+
+ ASSERT_EQ(get_ucall(vcpu, NULL), UCALL_SYNC);
+
+ vcpu_last_completed_iteration[vcpu_idx] = current_iteration;
+
+ /* 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))
+ ;
+ }
+}
+
+static void run_test(enum vm_guest_mode mode, void *unused)
+{
+ 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[ITERATIONS];
+ struct kvm_page_stats stats_clear_pass[ITERATIONS];
+ struct kvm_page_stats stats_dirty_logging_disabled;
+ struct kvm_page_stats stats_repopulated;
+
+ vm = memstress_create_vm(mode, VCPUS, guest_percpu_mem_size,
+ SLOTS, backing_src, false);
+
+ guest_num_pages = (VCPUS * guest_percpu_mem_size) >> vm->page_shift;
+ guest_num_pages = vm_adjust_num_guest_pages(mode, guest_num_pages);
+ host_num_pages = vm_num_host_pages(mode, guest_num_pages);
+ pages_per_slot = host_num_pages / SLOTS;
+
+ bitmaps = memstress_alloc_bitmaps(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 = -1;
+ host_quit = false;
+
+ for (i = 0; i < VCPUS; i++)
+ vcpu_last_completed_iteration[i] = -1;
+
+ memstress_start_vcpu_threads(VCPUS, vcpu_worker);
+
+ run_vcpu_iteration(vm);
+ get_page_stats(vm, &stats_populated, "populating memory");
+
+ /* Enable dirty logging */
+ memstress_enable_dirty_logging(vm, SLOTS);
+
+ get_page_stats(vm, &stats_dirty_logging_enabled, "enabling dirty logging");
+
+ while (iteration < ITERATIONS) {
+ run_vcpu_iteration(vm);
+ get_page_stats(vm, &stats_dirty_pass[iteration - 1],
+ "dirtying memory");
+
+ memstress_get_dirty_log(vm, bitmaps, SLOTS);
+
+ if (dirty_log_manual_caps) {
+ memstress_clear_dirty_log(vm, bitmaps, SLOTS, pages_per_slot);
+
+ get_page_stats(vm, &stats_clear_pass[iteration - 1], "clearing dirty log");
+ }
+ }
+
+ /* Disable dirty logging */
+ memstress_disable_dirty_logging(vm, SLOTS);
+
+ get_page_stats(vm, &stats_dirty_logging_disabled, "disabling dirty logging");
+
+ /* Run vCPUs again to fault pages back in. */
+ run_vcpu_iteration(vm);
+ get_page_stats(vm, &stats_repopulated, "repopulating memory");
+
+ /*
+ * 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(VCPUS);
+
+ memstress_free_bitmaps(bitmaps, 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) {
+ ASSERT_EQ(stats_clear_pass[0].hugepages, 0);
+ ASSERT_EQ(stats_clear_pass[0].pages_4k, total_4k_pages);
+ ASSERT_EQ(stats_dirty_logging_enabled.hugepages, stats_populated.hugepages);
+ } else {
+ ASSERT_EQ(stats_dirty_logging_enabled.hugepages, 0);
+ ASSERT_EQ(stats_dirty_logging_enabled.pages_4k, total_4k_pages);
+ }
+
+ /*
+ * 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.
+ */
+ ASSERT_EQ(stats_populated.pages_4k, stats_repopulated.pages_4k);
+ ASSERT_EQ(stats_populated.pages_2m, stats_repopulated.pages_2m);
+ ASSERT_EQ(stats_populated.pages_1g, stats_repopulated.pages_1g);
+}
+
+static void help(char *name)
+{
+ puts("");
+ printf("usage: %s [-h] [-b vcpu bytes] [-s mem type]\n",
+ name);
+ puts("");
+ 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("");
+}
+
+int main(int argc, char *argv[])
+{
+ int opt;
+
+ TEST_REQUIRE(get_kvm_param_bool("eager_page_split"));
+ TEST_REQUIRE(get_kvm_param_bool("tdp_mmu"));
+
+ while ((opt = getopt(argc, argv, "b:hs:")) != -1) {
+ switch (opt) {
+ case 'b':
+ guest_percpu_mem_size = parse_size(optarg);
+ break;
+ case 'h':
+ help(argv[0]);
+ exit(0);
+ case 's':
+ backing_src = parse_backing_src_type(optarg);
+ break;
+ default:
+ help(argv[0]);
+ exit(1);
+ }
+ }
+
+ if (!is_backing_src_hugetlb(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;
+ }
+
+ guest_modes_append_default();
+
+ dirty_log_manual_caps = 0;
+ for_each_guest_mode(run_test, NULL);
+
+ dirty_log_manual_caps =
+ kvm_check_cap(KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2);
+
+ if (dirty_log_manual_caps) {
+ dirty_log_manual_caps &= (KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE |
+ KVM_DIRTY_LOG_INITIALLY_SET);
+ for_each_guest_mode(run_test, NULL);
+ } else {
+ pr_info("Skipping testing with MANUAL_PROTECT as it is not supported");
+ }
+
+ return 0;
+}
--
2.39.1.456.gfc5497dd1b-goog
