Re: [RFC PATCH v5 10/10] KVM: selftests: Add a test for kvm page table code

Hi Drew,

BTW, any thoughts about the change in this patch? :)

Thanks, Yanan On 2021/3/23 21:52, Yanan Wang wrote:

This test serves as a performance tester and a bug reproducer for kvm page table code (GPA->HPA mappings), so it gives guidance for people trying to make some improvement for kvm.

The function guest_code() can cover the conditions where a single vcpu or multiple vcpus access guest pages within the same memory region, in three VM stages(before dirty logging, during dirty logging, after dirty logging). Besides, the backing src memory type(ANONYMOUS/THP/HUGETLB) of the tested memory region can be specified by users, which means normal page mappings or block mappings can be chosen by users to be created in the test.

If ANONYMOUS memory is specified, kvm will create normal page mappings for the tested memory region before dirty logging, and update attributes of the page mappings from RO to RW during dirty logging. If THP/HUGETLB memory is specified, kvm will create block mappings for the tested memory region before dirty logging, and split the blcok mappings into normal page mappings during dirty logging, and coalesce the page mappings back into block mappings after dirty logging is stopped.

So in summary, as a performance tester, this test can present the performance of kvm creating/updating normal page mappings, or the performance of kvm creating/splitting/recovering block mappings, through execution time.

When we need to coalesce the page mappings back to block mappings after dirty logging is stopped, we have to firstly invalidate *all* the TLB entries for the page mappings right before installation of the block entry, because a TLB conflict abort error could occur if we can't invalidate the TLB entries fully. We have hit this TLB conflict twice on aarch64 software implementation and fixed it. As this test can imulate process from dirty logging enabled to dirty logging stopped of a VM with block mappings, so it can also reproduce this TLB conflict abort due to inadequate TLB invalidation when coalescing tables.

Signed-off-by: Yanan Wang wangyanan55@huawei.com Reviewed-by: Ben Gardon bgardon@google.com

---

tools/testing/selftests/kvm/.gitignore | 1 + tools/testing/selftests/kvm/Makefile | 3 + .../selftests/kvm/kvm_page_table_test.c | 512 ++++++++++++++++++ 3 files changed, 516 insertions(+) create mode 100644 tools/testing/selftests/kvm/kvm_page_table_test.c

diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore index 32b87cc77c8e..137ab7273be6 100644 --- a/tools/testing/selftests/kvm/.gitignore +++ b/tools/testing/selftests/kvm/.gitignore @@ -35,6 +35,7 @@ /dirty_log_perf_test /hardware_disable_test /kvm_create_max_vcpus +/kvm_page_table_test /memslot_modification_stress_test /set_memory_region_test /steal_time diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile index a6d61f451f88..75dc57db36b4 100644 --- a/tools/testing/selftests/kvm/Makefile +++ b/tools/testing/selftests/kvm/Makefile @@ -69,6 +69,7 @@ TEST_GEN_PROGS_x86_64 += dirty_log_test TEST_GEN_PROGS_x86_64 += dirty_log_perf_test TEST_GEN_PROGS_x86_64 += hardware_disable_test TEST_GEN_PROGS_x86_64 += kvm_create_max_vcpus +TEST_GEN_PROGS_x86_64 += kvm_page_table_test TEST_GEN_PROGS_x86_64 += memslot_modification_stress_test TEST_GEN_PROGS_x86_64 += set_memory_region_test TEST_GEN_PROGS_x86_64 += steal_time @@ -79,6 +80,7 @@ TEST_GEN_PROGS_aarch64 += demand_paging_test TEST_GEN_PROGS_aarch64 += dirty_log_test TEST_GEN_PROGS_aarch64 += dirty_log_perf_test TEST_GEN_PROGS_aarch64 += kvm_create_max_vcpus +TEST_GEN_PROGS_aarch64 += kvm_page_table_test TEST_GEN_PROGS_aarch64 += set_memory_region_test TEST_GEN_PROGS_aarch64 += steal_time @@ -88,6 +90,7 @@ TEST_GEN_PROGS_s390x += s390x/sync_regs_test TEST_GEN_PROGS_s390x += demand_paging_test TEST_GEN_PROGS_s390x += dirty_log_test TEST_GEN_PROGS_s390x += kvm_create_max_vcpus +TEST_GEN_PROGS_s390x += kvm_page_table_test TEST_GEN_PROGS_s390x += set_memory_region_test TEST_GEN_PROGS += $(TEST_GEN_PROGS_$(UNAME_M)) diff --git a/tools/testing/selftests/kvm/kvm_page_table_test.c b/tools/testing/selftests/kvm/kvm_page_table_test.c new file mode 100644 index 000000000000..bbd5c489d61f --- /dev/null +++ b/tools/testing/selftests/kvm/kvm_page_table_test.c @@ -0,0 +1,512 @@ +// SPDX-License-Identifier: GPL-2.0 +/*

• • KVM page table test
• • Copyright (C) 2021, Huawei, Inc.
• • Make sure that THP has been enabled or enough HUGETLB pages with specific
• • page size have been pre-allocated on your system, if you are planning to
• • use hugepages to back the guest memory for testing.
• */

+#define _GNU_SOURCE /* for program_invocation_name */

+#include <stdio.h> +#include <stdlib.h> +#include <time.h> +#include <pthread.h> +#include <semaphore.h>

+#include "test_util.h" +#include "kvm_util.h" +#include "processor.h" +#include "guest_modes.h"

+#define TEST_MEM_SLOT_INDEX 1

+/* Default size(1GB) of the memory for testing */ +#define DEFAULT_TEST_MEM_SIZE (1 << 30)

+/* Default guest test virtual memory offset */ +#define DEFAULT_GUEST_TEST_MEM 0xc0000000

+/*

• • In our test, we use thread synchronization functions (e.g. sem_wait)
• • for time measurement and they can't fail at all, since a failure will
• • impact the time accuracy and vcpus will not run as what we expect.
• • So we will use safer versions of the functions.
• */

+#define sem_init_s(sem_ptr, ps, val) \

• TEST_ASSERT(sem_init(sem_ptr, ps, val) == 0, "Error in sem_init")

+#define sem_destroy_s(sem_ptr) \

• TEST_ASSERT(sem_destroy(sem_ptr) == 0, "Error in sem_destroy")

+#define sem_wait_s(sem_ptr) \

• TEST_ASSERT(sem_wait(sem_ptr) == 0, "Error in sem_wait")

+#define sem_post_s(sem_ptr) \

• TEST_ASSERT(sem_post(sem_ptr) == 0, "Error in sem_post")

+/* Different guest memory accessing stages */ +enum test_stage {

• KVM_BEFORE_MAPPINGS,
• KVM_CREATE_MAPPINGS,
• KVM_UPDATE_MAPPINGS,
• KVM_ADJUST_MAPPINGS,
• NUM_TEST_STAGES,

+};

+static const char * const test_stage_string[] = {

• "KVM_BEFORE_MAPPINGS",
• "KVM_CREATE_MAPPINGS",
• "KVM_UPDATE_MAPPINGS",
• "KVM_ADJUST_MAPPINGS",

+};

+struct perf_test_vcpu_args {

• int vcpu_id;
• bool vcpu_write;

+};

+struct perf_test_args {

• struct kvm_vm *vm;
• uint64_t guest_test_virt_mem;
• uint64_t host_page_size;
• uint64_t host_num_pages;
• uint64_t large_page_size;
• uint64_t large_num_pages;
• uint64_t host_pages_per_lpage;
• enum vm_mem_backing_src_type src_type;
• struct perf_test_vcpu_args vcpu_args[KVM_MAX_VCPUS];

+};

+/*

• • Guest variables. Use addr_gva2hva() if these variables need
• • to be changed in host.
• */

+static enum test_stage guest_test_stage;

+/* Host variables */ +static uint32_t nr_vcpus = 1; +static struct perf_test_args perf_test_args; +static enum test_stage *current_stage; +static bool host_quit;

+/* Whether the test stage is updated, or completed */ +static sem_t test_stage_updated; +static sem_t test_stage_completed;

+/*

• • Guest physical memory offset of the testing memory slot.
• • This will be set to the topmost valid physical address minus
• • the test memory size.
• */

+static uint64_t guest_test_phys_mem;

+/*

• • Guest virtual memory offset of the testing memory slot.
• • Must not conflict with identity mapped test code.
• */

+static uint64_t guest_test_virt_mem = DEFAULT_GUEST_TEST_MEM;

+static void guest_code(int vcpu_id) +{

• struct perf_test_args *p = &perf_test_args;
• struct perf_test_vcpu_args *vcpu_args = &p->vcpu_args[vcpu_id];
• enum vm_mem_backing_src_type src_type = p->src_type;
• uint64_t host_page_size = p->host_page_size;
• uint64_t host_num_pages = p->host_num_pages;
• uint64_t large_page_size = p->large_page_size;
• uint64_t large_num_pages = p->large_num_pages;
• uint64_t host_pages_per_lpage = p->host_pages_per_lpage;
• uint64_t half = host_pages_per_lpage / 2;
• bool vcpu_write;
• enum test_stage stage;
• uint64_t addr;
• int i, j;
• /* Make sure vCPU args data structure is not corrupt */
• GUEST_ASSERT(vcpu_args->vcpu_id == vcpu_id);
• vcpu_write = vcpu_args->vcpu_write;
• while (true) {

• stage = READ_ONCE(guest_test_stage);
  

• addr = perf_test_args.guest_test_virt_mem;
  

• switch (stage) {
  

• /*
  

•  * Before dirty logging, vCPUs concurrently access the first
  

•  * 8 bytes of each page (host page/large page) within the same
  

•  * memory region with different accessing types (read/write).
  

•  * Then KVM will create normal page mappings or huge block
  

•  * mappings for them.
  

•  */
  

• case KVM_CREATE_MAPPINGS:
  

• 	for (i = 0; i < large_num_pages; i++) {
  

• 		if (vcpu_write)
  

• 			*(uint64_t *)addr = 0x0123456789ABCDEF;
  

• 		else
  

• 			READ_ONCE(*(uint64_t *)addr);
  

• 		addr += large_page_size;
  

• 	}
  

• 	break;
  

• /*
  

•  * During dirty logging, KVM will only update attributes of the
  

•  * normal page mappings from RO to RW if memory backing src type
  

•  * is anonymous. In other cases, KVM will split the huge block
  

•  * mappings into normal page mappings if memory backing src type
  

•  * is THP or HUGETLB.
  

•  */
  

• case KVM_UPDATE_MAPPINGS:
  

• 	if (src_type == VM_MEM_SRC_ANONYMOUS) {
  

• 		for (i = 0; i < host_num_pages; i++) {
  

• 			*(uint64_t *)addr = 0x0123456789ABCDEF;
  

• 			addr += host_page_size;
  

• 		}
  

• 		break;
  

• 	}
  

• 	for (i = 0; i < large_num_pages; i++) {
  

• 		/*
  

• 		 * Write to the first host page in each large
  

• 		 * page region, and triger break of large pages.
  

• 		 */
  

• 		*(uint64_t *)addr = 0x0123456789ABCDEF;
  

• 		/*
  

• 		 * Access the middle host pages in each large
  

• 		 * page region. Since dirty logging is enabled,
  

• 		 * this will create new mappings at the smallest
  

• 		 * granularity.
  

• 		 */
  

• 		addr += host_page_size * half;
  

• 		for (j = half; j < host_pages_per_lpage; j++) {
  

• 			READ_ONCE(*(uint64_t *)addr);
  

• 			addr += host_page_size;
  

• 		}
  

• 	}
  

• 	break;
  

• /*
  

•  * After dirty logging is stopped, vCPUs concurrently read
  

•  * from every single host page. Then KVM will coalesce the
  

•  * split page mappings back to block mappings. And a TLB
  

•  * conflict abort could occur here if TLB entries of the
  

•  * page mappings are not fully invalidated.
  

•  */
  

• case KVM_ADJUST_MAPPINGS:
  

• 	for (i = 0; i < host_num_pages; i++) {
  

• 		READ_ONCE(*(uint64_t *)addr);
  

• 		addr += host_page_size;
  

• 	}
  

• 	break;
  

• default:
  

• 	break;
  

• }
  

• GUEST_SYNC(1);
  

• }

+}

+static void *vcpu_worker(void *data) +{

• int ret;
• struct perf_test_vcpu_args *vcpu_args = data;
• struct kvm_vm *vm = perf_test_args.vm;
• int vcpu_id = vcpu_args->vcpu_id;
• struct kvm_run *run;
• struct timespec start;
• struct timespec ts_diff;
• enum test_stage stage;
• vcpu_args_set(vm, vcpu_id, 1, vcpu_id);
• run = vcpu_state(vm, vcpu_id);
• while (!READ_ONCE(host_quit)) {

• clock_gettime(CLOCK_MONOTONIC_RAW, &start);
  

• ret = _vcpu_run(vm, vcpu_id);
  

• ts_diff = timespec_elapsed(start);
  

• TEST_ASSERT(ret == 0, "vcpu_run failed: %d\n", ret);
  

• TEST_ASSERT(get_ucall(vm, vcpu_id, NULL) == UCALL_SYNC,
  

• 	    "Invalid guest sync status: exit_reason=%s\n",
  

• 	    exit_reason_str(run->exit_reason));
  

• pr_debug("Got sync event from vCPU %d\n", vcpu_id);
  

• stage = READ_ONCE(*current_stage);
  

• /*
  

•  * Here we can know the execution time of every
  

•  * single vcpu running in different test stages.
  

•  */
  

• pr_debug("vCPU %d has completed stage %s\n"
  

• 	 "execution time is: %ld.%.9lds\n\n",
  

• 	 vcpu_id, test_stage_string[stage],
  

• 	 ts_diff.tv_sec, ts_diff.tv_nsec);
  

• sem_post_s(&test_stage_completed);
  

• sem_wait_s(&test_stage_updated);
  

• }
• return NULL;

+}

+struct test_params {

• uint64_t phys_offset;
• uint64_t test_mem_size;
• enum vm_mem_backing_src_type src_type;

+};

+static struct kvm_vm *pre_init_before_test(enum vm_guest_mode mode, void *arg) +{

• struct test_params *p = arg;
• struct perf_test_vcpu_args *vcpu_args;
• enum vm_mem_backing_src_type src_type = p->src_type;
• uint64_t large_page_size = get_backing_src_pagesz(src_type);
• uint64_t test_mem_size = p->test_mem_size, guest_num_pages;
• uint64_t guest_page_size = vm_guest_mode_params[mode].page_size;
• uint64_t host_page_size = getpagesize();
• uint64_t alignment;
• void *host_test_mem;
• struct kvm_vm *vm;
• int vcpu_id;
• /* Align up the test memory size */
• alignment = max(large_page_size, guest_page_size);
• test_mem_size = (test_mem_size + alignment - 1) & ~(alignment - 1);
• /* Create a VM with enough guest pages */
• guest_num_pages = test_mem_size / guest_page_size;
• vm = vm_create_with_vcpus(mode, nr_vcpus,

• 		  guest_num_pages, 0, guest_code, NULL);
  

• /* Align down GPA of the testing memslot */
• if (!p->phys_offset)

• guest_test_phys_mem = (vm_get_max_gfn(vm) - guest_num_pages) *
  

• 		       guest_page_size;
  

• else

• guest_test_phys_mem = p->phys_offset;
  

+#ifdef __s390x__

• alignment = max(0x100000, alignment);

+#endif

• guest_test_phys_mem &= ~(alignment - 1);
• /* Set up the shared data structure perf_test_args */
• perf_test_args.vm = vm;
• perf_test_args.guest_test_virt_mem = guest_test_virt_mem;
• perf_test_args.host_page_size = host_page_size;
• perf_test_args.host_num_pages = test_mem_size / host_page_size;
• perf_test_args.large_page_size = large_page_size;
• perf_test_args.large_num_pages = test_mem_size / large_page_size;
• perf_test_args.host_pages_per_lpage = large_page_size / host_page_size;
• perf_test_args.src_type = src_type;
• for (vcpu_id = 0; vcpu_id < KVM_MAX_VCPUS; vcpu_id++) {

• vcpu_args = &perf_test_args.vcpu_args[vcpu_id];
  

• vcpu_args->vcpu_id = vcpu_id;
  

• vcpu_args->vcpu_write = !(vcpu_id % 2);
  

• }
• /* Add an extra memory slot with specified backing src type */
• vm_userspace_mem_region_add(vm, src_type, guest_test_phys_mem,

• 		    TEST_MEM_SLOT_INDEX, guest_num_pages, 0);
  

• /* Do mapping(GVA->GPA) for the testing memory slot */
• virt_map(vm, guest_test_virt_mem, guest_test_phys_mem, guest_num_pages, 0);
• /* Cache the HVA pointer of the region */
• host_test_mem = addr_gpa2hva(vm, (vm_paddr_t)guest_test_phys_mem);
• /* Export shared structure perf_test_args to guest */
• ucall_init(vm, NULL);
• sync_global_to_guest(vm, perf_test_args);
• sem_init_s(&test_stage_updated, 0, 0);
• sem_init_s(&test_stage_completed, 0, 0);
• current_stage = addr_gva2hva(vm, (vm_vaddr_t)(&guest_test_stage));
• *current_stage = NUM_TEST_STAGES;
• pr_info("Testing guest mode: %s\n", vm_guest_mode_string(mode));
• pr_info("Testing memory backing src type: %s\n",

• vm_mem_backing_src_alias(src_type)->name);
  

• pr_info("Testing memory backing src granularity: 0x%lx\n",

• large_page_size);
  

• pr_info("Testing memory size(aligned): 0x%lx\n", test_mem_size);
• pr_info("Guest physical test memory offset: 0x%lx\n",

• guest_test_phys_mem);
  

• pr_info("Host virtual test memory offset: 0x%lx\n",

• (uint64_t)host_test_mem);
  

• pr_info("Number of testing vCPUs: %d\n", nr_vcpus);
• return vm;

+}

+/* Wake up all the vcpus to run new test stage */ +static void vcpus_start_new_stage(void) +{

• int vcpus;
• for (vcpus = 1; vcpus <= nr_vcpus; vcpus++)

• sem_post_s(&test_stage_updated);
  

• pr_debug("All vcpus have been notified to continue\n");

+}

+/* Wait for all the vcpus to complete new test stage */ +static void vcpus_complete_new_stage(enum test_stage stage) +{

• int vcpus;
• for (vcpus = 1; vcpus <= nr_vcpus; vcpus++) {

• sem_wait_s(&test_stage_completed);
  

• pr_debug("%d vcpus have completed stage %s\n",
  

• 	 vcpus, test_stage_string[stage]);
  

• }
• pr_debug("All vcpus have completed stage %s\n",

•  test_stage_string[stage]);
  

+}

+static void run_test(enum vm_guest_mode mode, void *arg) +{

• pthread_t *vcpu_threads;
• struct kvm_vm *vm;
• int vcpu_id;
• struct timespec start;
• struct timespec ts_diff;
• /* Create VM with vCPUs and make some pre-initialization */
• vm = pre_init_before_test(mode, arg);
• vcpu_threads = malloc(nr_vcpus * sizeof(*vcpu_threads));
• TEST_ASSERT(vcpu_threads, "Memory allocation failed");
• host_quit = false;
• *current_stage = KVM_BEFORE_MAPPINGS;
• for (vcpu_id = 0; vcpu_id < nr_vcpus; vcpu_id++) {

• pthread_create(&vcpu_threads[vcpu_id], NULL, vcpu_worker,
  

• 	       &perf_test_args.vcpu_args[vcpu_id]);
  

• }
• pr_info("Started all vCPUs successfully\n");
• vcpus_complete_new_stage(*current_stage);
• /* Test the stage of KVM creating mappings */
• *current_stage = KVM_CREATE_MAPPINGS;
• clock_gettime(CLOCK_MONOTONIC_RAW, &start);
• vcpus_start_new_stage();
• vcpus_complete_new_stage(*current_stage);
• ts_diff = timespec_elapsed(start);
• pr_info("KVM_CREATE_MAPPINGS: total execution time: %ld.%.9lds\n\n",

• ts_diff.tv_sec, ts_diff.tv_nsec);
  

• /* Test the stage of KVM updating mappings */
• vm_mem_region_set_flags(vm, TEST_MEM_SLOT_INDEX,

• 		KVM_MEM_LOG_DIRTY_PAGES);
  

• *current_stage = KVM_UPDATE_MAPPINGS;
• clock_gettime(CLOCK_MONOTONIC_RAW, &start);
• vcpus_start_new_stage();
• vcpus_complete_new_stage(*current_stage);
• ts_diff = timespec_elapsed(start);
• pr_info("KVM_UPDATE_MAPPINGS: total execution time: %ld.%.9lds\n\n",

• ts_diff.tv_sec, ts_diff.tv_nsec);
  

• /* Test the stage of KVM adjusting mappings */
• vm_mem_region_set_flags(vm, TEST_MEM_SLOT_INDEX, 0);
• *current_stage = KVM_ADJUST_MAPPINGS;
• clock_gettime(CLOCK_MONOTONIC_RAW, &start);
• vcpus_start_new_stage();
• vcpus_complete_new_stage(*current_stage);
• ts_diff = timespec_elapsed(start);
• pr_info("KVM_ADJUST_MAPPINGS: total execution time: %ld.%.9lds\n\n",

• ts_diff.tv_sec, ts_diff.tv_nsec);
  

• /* Tell the vcpu thread to quit */
• host_quit = true;
• vcpus_start_new_stage();
• for (vcpu_id = 0; vcpu_id < nr_vcpus; vcpu_id++)

• pthread_join(vcpu_threads[vcpu_id], NULL);
  

• sem_destroy_s(&test_stage_updated);
• sem_destroy_s(&test_stage_completed);
• free(vcpu_threads);
• ucall_uninit(vm);
• kvm_vm_free(vm);

+}

+static void help(char *name) +{

• puts("");
• printf("usage: %s [-h] [-p offset] [-m mode] "

•       "[-b mem-size] [-v vcpus] [-s mem-type]\n", name);
  

• puts("");
• printf(" -p: specify guest physical test memory offset\n"

•       "     Warning: a low offset can conflict with the loaded test code.\n");
  

• guest_modes_help();
• printf(" -b: specify size of the memory region for testing. e.g. 10M or 3G.\n"

•       "     (default: 1G)\n");
  

• printf(" -v: specify the number of vCPUs to run\n"

•       "     (default: 1)\n");
  

• printf(" -s: specify the type of memory that should be used to\n"

•       "     back the guest data region.\n"
  

•       "     (default: anonymous)\n\n");
  

• backing_src_help();
• puts("");
• exit(0);

+}

+int main(int argc, char *argv[]) +{

• int max_vcpus = kvm_check_cap(KVM_CAP_MAX_VCPUS);
• struct test_params p = {

• .test_mem_size = DEFAULT_TEST_MEM_SIZE,
  

• .src_type = VM_MEM_SRC_ANONYMOUS,
  

• };
• int opt;
• guest_modes_append_default();
• while ((opt = getopt(argc, argv, "hp:m:b:v:s:")) != -1) {

• switch (opt) {
  

• case 'p':
  

• 	p.phys_offset = strtoull(optarg, NULL, 0);
  

• 	break;
  

• case 'm':
  

• 	guest_modes_cmdline(optarg);
  

• 	break;
  

• case 'b':
  

• 	p.test_mem_size = parse_size(optarg);
  

• 	break;
  

• case 'v':
  

• 	nr_vcpus = atoi(optarg);
  

• 	TEST_ASSERT(nr_vcpus > 0 && nr_vcpus <= max_vcpus,
  

• 		    "Invalid number of vcpus, must be between 1 and %d", max_vcpus);
  

• 	break;
  

• case 's':
  

• 	p.src_type = parse_backing_src_type(optarg);
  

• 	break;
  

• case 'h':
  

• default:
  

• 	help(argv[0]);
  

• 	break;
  

• }
  

• }
• for_each_guest_mode(run_test, &p);
• return 0;

+}