[PATCH v4 0/2] selftests: KVM: Add a test for eager page splitting

[PATCH v4 0/2] selftests: KVM: Add a test for eager page splitting

[Ben Gardon]

David Matlack recently added a feature known as eager page splitting
to x86 KVM. This feature improves vCPU performance during dirty
logging because the splitting operation is moved out of the page
fault path, avoiding EPT/NPT violations or allowing the vCPU threads
to resolve the violation in the fast path.

While this feature is a great performance improvement, it does not
have adequate testing in KVM selftests. Add a test to provide coverage
of eager page splitting.

Patch 1 is a quick refactor to be able to re-use some code from
dirty_log_perf_test.
Patch 2 adds the actual test.

V1->V2:
	Run test in multiple modes, as suggested by David and Ricardo
	Cleanups from shameful copy-pasta, as suggested by David
V2->V3:
	Removed copyright notice from the top of
	dirty_log_page_splitting.c
	Adopted ASSERT_EQ for test assertions
	Now skipping testing with MANUAL_PROTECT if unsupported
V3->V4:
	Added the copyright notices back. Thanks Vipin for the right
	thing to do there.

Ben Gardon (2):
  selftests: KVM: Move dirty logging functions to memstress.(c|h)
  selftests: KVM: Add dirty logging page splitting test

 tools/testing/selftests/kvm/Makefile          |   1 +
 .../selftests/kvm/dirty_log_perf_test.c       |  84 +-----
 .../selftests/kvm/include/kvm_util_base.h     |   1 +
 .../testing/selftests/kvm/include/memstress.h |   8 +
 tools/testing/selftests/kvm/lib/kvm_util.c    |   5 +
 tools/testing/selftests/kvm/lib/memstress.c   |  72 +++++
 .../x86_64/dirty_log_page_splitting_test.c    | 257 ++++++++++++++++++
 7 files changed, 351 insertions(+), 77 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/x86_64/dirty_log_page_splitting_test.c

-- 
2.39.1.456.gfc5497dd1b-goog

[PATCH v4 1/2] selftests: KVM: Move dirty logging functions to memstress.(c|h)

[Ben Gardon]

Move some helper functions from dirty_log_perf_test.c to the memstress
library so that they can be used in a future commit which tests page
splitting during dirty logging.

Reviewed-by: Vipin Sharma <vipinsh@google.com>

Signed-off-by: Ben Gardon <bgardon@google.com>
---
 .../selftests/kvm/dirty_log_perf_test.c       | 84 ++-----------------
 .../testing/selftests/kvm/include/memstress.h |  8 ++
 tools/testing/selftests/kvm/lib/memstress.c   | 72 ++++++++++++++++
 3 files changed, 87 insertions(+), 77 deletions(-)

diff --git a/tools/testing/selftests/kvm/dirty_log_perf_test.c b/tools/testing/selftests/kvm/dirty_log_perf_test.c
index e9d6d1aecf89c..416719e205183 100644
--- a/tools/testing/selftests/kvm/dirty_log_perf_test.c
+++ b/tools/testing/selftests/kvm/dirty_log_perf_test.c
@@ -136,77 +136,6 @@ struct test_params {
 	bool random_access;
 };
 
-static void toggle_dirty_logging(struct kvm_vm *vm, int slots, bool enable)
-{
-	int i;
-
-	for (i = 0; i < slots; i++) {
-		int slot = MEMSTRESS_MEM_SLOT_INDEX + i;
-		int flags = enable ? KVM_MEM_LOG_DIRTY_PAGES : 0;
-
-		vm_mem_region_set_flags(vm, slot, flags);
-	}
-}
-
-static inline void enable_dirty_logging(struct kvm_vm *vm, int slots)
-{
-	toggle_dirty_logging(vm, slots, true);
-}
-
-static inline void disable_dirty_logging(struct kvm_vm *vm, int slots)
-{
-	toggle_dirty_logging(vm, slots, false);
-}
-
-static void get_dirty_log(struct kvm_vm *vm, unsigned long *bitmaps[], int slots)
-{
-	int i;
-
-	for (i = 0; i < slots; i++) {
-		int slot = MEMSTRESS_MEM_SLOT_INDEX + i;
-
-		kvm_vm_get_dirty_log(vm, slot, bitmaps[i]);
-	}
-}
-
-static void clear_dirty_log(struct kvm_vm *vm, unsigned long *bitmaps[],
-			    int slots, uint64_t pages_per_slot)
-{
-	int i;
-
-	for (i = 0; i < slots; i++) {
-		int slot = MEMSTRESS_MEM_SLOT_INDEX + i;
-
-		kvm_vm_clear_dirty_log(vm, slot, bitmaps[i], 0, pages_per_slot);
-	}
-}
-
-static unsigned long **alloc_bitmaps(int slots, uint64_t pages_per_slot)
-{
-	unsigned long **bitmaps;
-	int i;
-
-	bitmaps = malloc(slots * sizeof(bitmaps[0]));
-	TEST_ASSERT(bitmaps, "Failed to allocate bitmaps array.");
-
-	for (i = 0; i < slots; i++) {
-		bitmaps[i] = bitmap_zalloc(pages_per_slot);
-		TEST_ASSERT(bitmaps[i], "Failed to allocate slot bitmap.");
-	}
-
-	return bitmaps;
-}
-
-static void free_bitmaps(unsigned long *bitmaps[], int slots)
-{
-	int i;
-
-	for (i = 0; i < slots; i++)
-		free(bitmaps[i]);
-
-	free(bitmaps);
-}
-
 static void run_test(enum vm_guest_mode mode, void *arg)
 {
 	struct test_params *p = arg;
@@ -236,7 +165,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
 	host_num_pages = vm_num_host_pages(mode, guest_num_pages);
 	pages_per_slot = host_num_pages / p->slots;
 
-	bitmaps = alloc_bitmaps(p->slots, pages_per_slot);
+	bitmaps = memstress_alloc_bitmaps(p->slots, pages_per_slot);
 
 	if (dirty_log_manual_caps)
 		vm_enable_cap(vm, KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2,
@@ -277,7 +206,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
 
 	/* Enable dirty logging */
 	clock_gettime(CLOCK_MONOTONIC, &start);
-	enable_dirty_logging(vm, p->slots);
+	memstress_enable_dirty_logging(vm, p->slots);
 	ts_diff = timespec_elapsed(start);
 	pr_info("Enabling dirty logging time: %ld.%.9lds\n\n",
 		ts_diff.tv_sec, ts_diff.tv_nsec);
@@ -306,7 +235,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
 			iteration, ts_diff.tv_sec, ts_diff.tv_nsec);
 
 		clock_gettime(CLOCK_MONOTONIC, &start);
-		get_dirty_log(vm, bitmaps, p->slots);
+		memstress_get_dirty_log(vm, bitmaps, p->slots);
 		ts_diff = timespec_elapsed(start);
 		get_dirty_log_total = timespec_add(get_dirty_log_total,
 						   ts_diff);
@@ -315,7 +244,8 @@ static void run_test(enum vm_guest_mode mode, void *arg)
 
 		if (dirty_log_manual_caps) {
 			clock_gettime(CLOCK_MONOTONIC, &start);
-			clear_dirty_log(vm, bitmaps, p->slots, pages_per_slot);
+			memstress_clear_dirty_log(vm, bitmaps, p->slots,
+						  pages_per_slot);
 			ts_diff = timespec_elapsed(start);
 			clear_dirty_log_total = timespec_add(clear_dirty_log_total,
 							     ts_diff);
@@ -334,7 +264,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
 
 	/* Disable dirty logging */
 	clock_gettime(CLOCK_MONOTONIC, &start);
-	disable_dirty_logging(vm, p->slots);
+	memstress_disable_dirty_logging(vm, p->slots);
 	ts_diff = timespec_elapsed(start);
 	pr_info("Disabling dirty logging time: %ld.%.9lds\n",
 		ts_diff.tv_sec, ts_diff.tv_nsec);
@@ -359,7 +289,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
 			clear_dirty_log_total.tv_nsec, avg.tv_sec, avg.tv_nsec);
 	}
 
-	free_bitmaps(bitmaps, p->slots);
+	memstress_free_bitmaps(bitmaps, p->slots);
 	arch_cleanup_vm(vm);
 	memstress_destroy_vm(vm);
 }
diff --git a/tools/testing/selftests/kvm/include/memstress.h b/tools/testing/selftests/kvm/include/memstress.h
index 72e3e358ef7bd..ce4e603050eaa 100644
--- a/tools/testing/selftests/kvm/include/memstress.h
+++ b/tools/testing/selftests/kvm/include/memstress.h
@@ -72,4 +72,12 @@ void memstress_guest_code(uint32_t vcpu_id);
 uint64_t memstress_nested_pages(int nr_vcpus);
 void memstress_setup_nested(struct kvm_vm *vm, int nr_vcpus, struct kvm_vcpu *vcpus[]);
 
+void memstress_enable_dirty_logging(struct kvm_vm *vm, int slots);
+void memstress_disable_dirty_logging(struct kvm_vm *vm, int slots);
+void memstress_get_dirty_log(struct kvm_vm *vm, unsigned long *bitmaps[], int slots);
+void memstress_clear_dirty_log(struct kvm_vm *vm, unsigned long *bitmaps[],
+			       int slots, uint64_t pages_per_slot);
+unsigned long **memstress_alloc_bitmaps(int slots, uint64_t pages_per_slot);
+void memstress_free_bitmaps(unsigned long *bitmaps[], int slots);
+
 #endif /* SELFTEST_KVM_MEMSTRESS_H */
diff --git a/tools/testing/selftests/kvm/lib/memstress.c b/tools/testing/selftests/kvm/lib/memstress.c
index 5f1d3173c238c..3632956c6bcf5 100644
--- a/tools/testing/selftests/kvm/lib/memstress.c
+++ b/tools/testing/selftests/kvm/lib/memstress.c
@@ -5,6 +5,7 @@
 #define _GNU_SOURCE
 
 #include <inttypes.h>
+#include <linux/bitmap.h>
 
 #include "kvm_util.h"
 #include "memstress.h"
@@ -320,3 +321,74 @@ void memstress_join_vcpu_threads(int nr_vcpus)
 	for (i = 0; i < nr_vcpus; i++)
 		pthread_join(vcpu_threads[i].thread, NULL);
 }
+
+static void toggle_dirty_logging(struct kvm_vm *vm, int slots, bool enable)
+{
+	int i;
+
+	for (i = 0; i < slots; i++) {
+		int slot = MEMSTRESS_MEM_SLOT_INDEX + i;
+		int flags = enable ? KVM_MEM_LOG_DIRTY_PAGES : 0;
+
+		vm_mem_region_set_flags(vm, slot, flags);
+	}
+}
+
+void memstress_enable_dirty_logging(struct kvm_vm *vm, int slots)
+{
+	toggle_dirty_logging(vm, slots, true);
+}
+
+void memstress_disable_dirty_logging(struct kvm_vm *vm, int slots)
+{
+	toggle_dirty_logging(vm, slots, false);
+}
+
+void memstress_get_dirty_log(struct kvm_vm *vm, unsigned long *bitmaps[], int slots)
+{
+	int i;
+
+	for (i = 0; i < slots; i++) {
+		int slot = MEMSTRESS_MEM_SLOT_INDEX + i;
+
+		kvm_vm_get_dirty_log(vm, slot, bitmaps[i]);
+	}
+}
+
+void memstress_clear_dirty_log(struct kvm_vm *vm, unsigned long *bitmaps[],
+			       int slots, uint64_t pages_per_slot)
+{
+	int i;
+
+	for (i = 0; i < slots; i++) {
+		int slot = MEMSTRESS_MEM_SLOT_INDEX + i;
+
+		kvm_vm_clear_dirty_log(vm, slot, bitmaps[i], 0, pages_per_slot);
+	}
+}
+
+unsigned long **memstress_alloc_bitmaps(int slots, uint64_t pages_per_slot)
+{
+	unsigned long **bitmaps;
+	int i;
+
+	bitmaps = malloc(slots * sizeof(bitmaps[0]));
+	TEST_ASSERT(bitmaps, "Failed to allocate bitmaps array.");
+
+	for (i = 0; i < slots; i++) {
+		bitmaps[i] = bitmap_zalloc(pages_per_slot);
+		TEST_ASSERT(bitmaps[i], "Failed to allocate slot bitmap.");
+	}
+
+	return bitmaps;
+}
+
+void memstress_free_bitmaps(unsigned long *bitmaps[], int slots)
+{
+	int i;
+
+	for (i = 0; i < slots; i++)
+		free(bitmaps[i]);
+
+	free(bitmaps);
+}
-- 
2.39.1.456.gfc5497dd1b-goog

[PATCH v4 2/2] selftests: KVM: Add dirty logging page splitting test

[Ben Gardon]

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.

Signed-off-by: Ben Gardon <bgardon@google.com>
---
 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    | 257 ++++++++++++++++++
 4 files changed, 264 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..240e7d220afa8
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86_64/dirty_log_page_splitting_test.c
@@ -0,0 +1,257 @@
+// 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_vcpus_get_page_stats(struct kvm_vm *vm, struct kvm_page_stats *stats, const char *stage)
+{
+	int i;
+
+	iteration++;
+	for (i = 0; i < VCPUS; i++) {
+		while (READ_ONCE(vcpu_last_completed_iteration[i]) !=
+		       iteration)
+			;
+	}
+
+	get_page_stats(vm, stats, stage);
+}
+
+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_vcpus_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_vcpus_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_vcpus_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);
+	}
+
+	return 0;
+}
-- 
2.39.1.456.gfc5497dd1b-goog

Re: [PATCH v4 2/2] selftests: KVM: Add dirty logging page splitting test

[Vipin Sharma]

On Wed, Jan 25, 2023 at 10:23 AM Ben Gardon <bgardon@google.com> wrote:

> +static void run_vcpus_get_page_stats(struct kvm_vm *vm, struct kvm_page_stats *stats, const char *stage)
> +{
> +       int i;
> +
> +       iteration++;
> +       for (i = 0; i < VCPUS; i++) {
> +               while (READ_ONCE(vcpu_last_completed_iteration[i]) !=
> +                      iteration)
> +                       ;
> +       }
> +
> +       get_page_stats(vm, stats, stage);

get_page_stats() is already called in run_test() explicitly for other
stats. I think it's better to split this function and make the flow
like:

run_vcpus_till_iteration(iteration++);
get_page_stats(vm, &stats_populated, "populating memory");

This makes it easy to follow run_test_till_iteration() and easy to see
where stats are collected. run_test_till_iteration() can also be a
library function used by other tests like dirty_log_perf_test


> +       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);
> +       }

Should there be a message to show  that this capability is not tested
as it is not available?
Or, there can be a command line option to explicitly provide intent of
testing combined,  split modes, or both? Then test can error out
accordingly.

Re: [PATCH v4 2/2] selftests: KVM: Add dirty logging page splitting test

[Ben Gardon]

On Thu, Jan 26, 2023 at 12:06 PM Vipin Sharma <vipinsh@google.com> wrote:
>
> On Wed, Jan 25, 2023 at 10:23 AM Ben Gardon <bgardon@google.com> wrote:
>
> > +static void run_vcpus_get_page_stats(struct kvm_vm *vm, struct kvm_page_stats *stats, const char *stage)
> > +{
> > +       int i;
> > +
> > +       iteration++;
> > +       for (i = 0; i < VCPUS; i++) {
> > +               while (READ_ONCE(vcpu_last_completed_iteration[i]) !=
> > +                      iteration)
> > +                       ;
> > +       }
> > +
> > +       get_page_stats(vm, stats, stage);
>
> get_page_stats() is already called in run_test() explicitly for other
> stats. I think it's better to split this function and make the flow
> like:
>
> run_vcpus_till_iteration(iteration++);
> get_page_stats(vm, &stats_populated, "populating memory");
>
> This makes it easy to follow run_test_till_iteration() and easy to see
> where stats are collected. run_test_till_iteration() can also be a
> library function used by other tests like dirty_log_perf_test

Yeah, either way works. We can do it all in the run_tests function as
I originally had or we can have the run vcpus and get stats in a
helper as David suggested or we can separate run_vcpus and get_stats
helpers as you're suggesting. I don't think it makes much of a
difference.
If you feel strongly I can send out another iteration of this test.

>
>
> > +       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);
> > +       }
>
> Should there be a message to show  that this capability is not tested
> as it is not available?
> Or, there can be a command line option to explicitly provide intent of
> testing combined,  split modes, or both? Then test can error out
> accordingly.

Sure, that would work too. If I send another version of this series I
can add a skip message, but I don't want to re-add an option to
specify whether to run with MANUAL_PROTECT, because that's what I had
originally and then David suggested I remove it and just always run
both.

Re: [PATCH v4 2/2] selftests: KVM: Add dirty logging page splitting test

[Vipin Sharma]

On Thu, Jan 26, 2023 at 2:52 PM Ben Gardon <bgardon@google.com> wrote:
>
> On Thu, Jan 26, 2023 at 12:06 PM Vipin Sharma <vipinsh@google.com> wrote:
> >
> > On Wed, Jan 25, 2023 at 10:23 AM Ben Gardon <bgardon@google.com> wrote:
> >
> > > +static void run_vcpus_get_page_stats(struct kvm_vm *vm, struct kvm_page_stats *stats, const char *stage)
> > > +{
> > > +       int i;
> > > +
> > > +       iteration++;
> > > +       for (i = 0; i < VCPUS; i++) {
> > > +               while (READ_ONCE(vcpu_last_completed_iteration[i]) !=
> > > +                      iteration)
> > > +                       ;
> > > +       }
> > > +
> > > +       get_page_stats(vm, stats, stage);
> >
> > get_page_stats() is already called in run_test() explicitly for other
> > stats. I think it's better to split this function and make the flow
> > like:
> >
> > run_vcpus_till_iteration(iteration++);
> > get_page_stats(vm, &stats_populated, "populating memory");
> >
> > This makes it easy to follow run_test_till_iteration() and easy to see
> > where stats are collected. run_test_till_iteration() can also be a
> > library function used by other tests like dirty_log_perf_test
>
> Yeah, either way works. We can do it all in the run_tests function as
> I originally had or we can have the run vcpus and get stats in a
> helper as David suggested or we can separate run_vcpus and get_stats
> helpers as you're suggesting. I don't think it makes much of a
> difference.
> If you feel strongly I can send out another iteration of this test.
>

I should have read David's comment and responded in that version.
No strong feelings. It is up to you.

> >
> >
> > > +       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);
> > > +       }
> >
> > Should there be a message to show  that this capability is not tested
> > as it is not available?
> > Or, there can be a command line option to explicitly provide intent of
> > testing combined,  split modes, or both? Then test can error out
> > accordingly.
>
> Sure, that would work too. If I send another version of this series I
> can add a skip message, but I don't want to re-add an option to
> specify whether to run with MANUAL_PROTECT, because that's what I had
> originally and then David suggested I remove it and just always run
> both.

Sounds good.

Reviewed-By: Vipin Sharma <vipinsh@google.com>

Re: [PATCH v4 2/2] selftests: KVM: Add dirty logging page splitting test

[Ben Gardon]

On Thu, Jan 26, 2023 at 3:04 PM Vipin Sharma <vipinsh@google.com> wrote:
>
> On Thu, Jan 26, 2023 at 2:52 PM Ben Gardon <bgardon@google.com> wrote:
> >
> > On Thu, Jan 26, 2023 at 12:06 PM Vipin Sharma <vipinsh@google.com> wrote:
> > >
> > > On Wed, Jan 25, 2023 at 10:23 AM Ben Gardon <bgardon@google.com> wrote:
> > >
> > > > +static void run_vcpus_get_page_stats(struct kvm_vm *vm, struct kvm_page_stats *stats, const char *stage)
> > > > +{
> > > > +       int i;
> > > > +
> > > > +       iteration++;
> > > > +       for (i = 0; i < VCPUS; i++) {
> > > > +               while (READ_ONCE(vcpu_last_completed_iteration[i]) !=
> > > > +                      iteration)
> > > > +                       ;
> > > > +       }
> > > > +
> > > > +       get_page_stats(vm, stats, stage);
> > >
> > > get_page_stats() is already called in run_test() explicitly for other
> > > stats. I think it's better to split this function and make the flow
> > > like:
> > >
> > > run_vcpus_till_iteration(iteration++);
> > > get_page_stats(vm, &stats_populated, "populating memory");
> > >
> > > This makes it easy to follow run_test_till_iteration() and easy to see
> > > where stats are collected. run_test_till_iteration() can also be a
> > > library function used by other tests like dirty_log_perf_test
> >
> > Yeah, either way works. We can do it all in the run_tests function as
> > I originally had or we can have the run vcpus and get stats in a
> > helper as David suggested or we can separate run_vcpus and get_stats
> > helpers as you're suggesting. I don't think it makes much of a
> > difference.
> > If you feel strongly I can send out another iteration of this test.
> >
>
> I should have read David's comment and responded in that version.
> No strong feelings. It is up to you.

No worries, it probably would have been easier to track down if I had
links in the cover letter. :)

>
> > >
> > >
> > > > +       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);
> > > > +       }
> > >
> > > Should there be a message to show  that this capability is not tested
> > > as it is not available?
> > > Or, there can be a command line option to explicitly provide intent of
> > > testing combined,  split modes, or both? Then test can error out
> > > accordingly.
> >
> > Sure, that would work too. If I send another version of this series I
> > can add a skip message, but I don't want to re-add an option to
> > specify whether to run with MANUAL_PROTECT, because that's what I had
> > originally and then David suggested I remove it and just always run
> > both.
>
> Sounds good.
>
> Reviewed-By: Vipin Sharma <vipinsh@google.com>

Thanks!

Re: [PATCH v4 2/2] selftests: KVM: Add dirty logging page splitting test

[David Matlack]

On Thu, Jan 26, 2023 at 3:12 PM Ben Gardon <bgardon@google.com> wrote:
>
> On Thu, Jan 26, 2023 at 3:04 PM Vipin Sharma <vipinsh@google.com> wrote:
> >
> > On Thu, Jan 26, 2023 at 2:52 PM Ben Gardon <bgardon@google.com> wrote:
> > >
> > > On Thu, Jan 26, 2023 at 12:06 PM Vipin Sharma <vipinsh@google.com> wrote:
> > > >
> > > > On Wed, Jan 25, 2023 at 10:23 AM Ben Gardon <bgardon@google.com> wrote:
> > > >
> > > > > +static void run_vcpus_get_page_stats(struct kvm_vm *vm, struct kvm_page_stats *stats, const char *stage)
> > > > > +{
> > > > > +       int i;
> > > > > +
> > > > > +       iteration++;
> > > > > +       for (i = 0; i < VCPUS; i++) {
> > > > > +               while (READ_ONCE(vcpu_last_completed_iteration[i]) !=
> > > > > +                      iteration)
> > > > > +                       ;
> > > > > +       }
> > > > > +
> > > > > +       get_page_stats(vm, stats, stage);
> > > >
> > > > get_page_stats() is already called in run_test() explicitly for other
> > > > stats. I think it's better to split this function and make the flow
> > > > like:
> > > >
> > > > run_vcpus_till_iteration(iteration++);
> > > > get_page_stats(vm, &stats_populated, "populating memory");
> > > >
> > > > This makes it easy to follow run_test_till_iteration() and easy to see
> > > > where stats are collected. run_test_till_iteration() can also be a
> > > > library function used by other tests like dirty_log_perf_test
> > >
> > > Yeah, either way works. We can do it all in the run_tests function as
> > > I originally had or we can have the run vcpus and get stats in a
> > > helper as David suggested or we can separate run_vcpus and get_stats
> > > helpers as you're suggesting. I don't think it makes much of a
> > > difference.
> > > If you feel strongly I can send out another iteration of this test.
> > >
> >
> > I should have read David's comment and responded in that version.
> > No strong feelings. It is up to you.
>
> No worries, it probably would have been easier to track down if I had
> links in the cover letter. :)

I mostly wanted the loop to go in a helper and threw in the stats
without really thinking about it. Now that I see it I like Vipin's
idea of having the stats call separate.

Re: [PATCH v4 0/2] selftests: KVM: Add a test for eager page splitting

[Vipin Sharma]

On Wed, Jan 25, 2023 at 10:23 AM Ben Gardon <bgardon@google.com> wrote:
>
> David Matlack recently added a feature known as eager page splitting
> to x86 KVM. This feature improves vCPU performance during dirty
> logging because the splitting operation is moved out of the page
> fault path, avoiding EPT/NPT violations or allowing the vCPU threads
> to resolve the violation in the fast path.
>
> While this feature is a great performance improvement, it does not
> have adequate testing in KVM selftests. Add a test to provide coverage
> of eager page splitting.
>
> Patch 1 is a quick refactor to be able to re-use some code from
> dirty_log_perf_test.
> Patch 2 adds the actual test.
>
> V1->V2:
Links of previous versions of patches are helpful and avoid searching
if one wants to read previous discussions.

>         Run test in multiple modes, as suggested by David and Ricardo
>         Cleanups from shameful copy-pasta, as suggested by David
> V2->V3:
>         Removed copyright notice from the top of
>         dirty_log_page_splitting.c
>         Adopted ASSERT_EQ for test assertions
>         Now skipping testing with MANUAL_PROTECT if unsupported
> V3->V4:
>         Added the copyright notices back. Thanks Vipin for the right
>         thing to do there.
>
> Ben Gardon (2):
>   selftests: KVM: Move dirty logging functions to memstress.(c|h)
>   selftests: KVM: Add dirty logging page splitting test
>
>  tools/testing/selftests/kvm/Makefile          |   1 +
>  .../selftests/kvm/dirty_log_perf_test.c       |  84 +-----
>  .../selftests/kvm/include/kvm_util_base.h     |   1 +
>  .../testing/selftests/kvm/include/memstress.h |   8 +
>  tools/testing/selftests/kvm/lib/kvm_util.c    |   5 +
>  tools/testing/selftests/kvm/lib/memstress.c   |  72 +++++
>  .../x86_64/dirty_log_page_splitting_test.c    | 257 ++++++++++++++++++
>  7 files changed, 351 insertions(+), 77 deletions(-)
>  create mode 100644 tools/testing/selftests/kvm/x86_64/dirty_log_page_splitting_test.c
>
> --
> 2.39.1.456.gfc5497dd1b-goog
>

Re: [PATCH v4 0/2] selftests: KVM: Add a test for eager page splitting

[Sean Christopherson]

On Thu, Jan 26, 2023, Vipin Sharma wrote:
> On Wed, Jan 25, 2023 at 10:23 AM Ben Gardon <bgardon@google.com> wrote:
> >
> > David Matlack recently added a feature known as eager page splitting
> > to x86 KVM. This feature improves vCPU performance during dirty
> > logging because the splitting operation is moved out of the page
> > fault path, avoiding EPT/NPT violations or allowing the vCPU threads
> > to resolve the violation in the fast path.
> >
> > While this feature is a great performance improvement, it does not
> > have adequate testing in KVM selftests. Add a test to provide coverage
> > of eager page splitting.
> >
> > Patch 1 is a quick refactor to be able to re-use some code from
> > dirty_log_perf_test.
> > Patch 2 adds the actual test.
> >
> > V1->V2:
> Links of previous versions of patches are helpful and avoid searching
> if one wants to read previous discussions.

+1

I also strongly prefer versioning to go from newest=>oldest instead of oldest=>newest,
that way reviewers can quickly see the delta for _this_ version.  It doesn't matter
too much when the delta is small, but oldest=>newest gets _really_ annoying the
longer the list gets.

> >         Run test in multiple modes, as suggested by David and Ricardo
> >         Cleanups from shameful copy-pasta, as suggested by David
> > V2->V3:
> >         Removed copyright notice from the top of
> >         dirty_log_page_splitting.c
> >         Adopted ASSERT_EQ for test assertions
> >         Now skipping testing with MANUAL_PROTECT if unsupported
> > V3->V4:
> >         Added the copyright notices back. Thanks Vipin for the right
> >         thing to do there.

Please do _something_ to differentiate line items.  I would also drop the tabs in
favor of a single space or two so that you don't end up wrapping so much.  E.g.
(choose your preferred flavor of list item identifiers)

V3->V4:
  - Added the copyright notices back. Thanks Vipin for the right thing to do
    there

V2->V3:
  - Removed copyright notice from the top of dirty_log_page_splitting.c
  - Adopted ASSERT_EQ for test assertions
  - Now skipping testing with MANUAL_PROTECT if unsupported