Re: [RFC PATCH 2/2] KVM: selftests: Add a test for kvm page table code

["wangyanan (Y)" <wangyanan55@huawei.com>]

Hi Vitaly,

On 2021/2/8 18:21, Vitaly Kuznetsov wrote:
> Yanan Wang <wangyanan55@huawei.com> writes:
>
>> 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() is designed to cover conditions where a single vcpu
>> or multiple vcpus access guest pages within the same memory range, in three
>> VM stages(before dirty-logging, during dirty-logging, after dirty-logging).
>> Besides, the backing source 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 use of ANONYMOUS memory is specified, kvm will create 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 use of THP/HUGETLB memory is
>> specified, kvm will create block mappings for the tested memory region before
>> dirty-logging, and split the blcok mappings into 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>
> This looks like a really useful thing, thanks! A few nitpicks below.
>
>> ---
>>   tools/testing/selftests/kvm/Makefile          |   3 +
>>   .../selftests/kvm/kvm_page_table_test.c       | 518 ++++++++++++++++++
>>   2 files changed, 521 insertions(+)
>>   create mode 100644 tools/testing/selftests/kvm/kvm_page_table_test.c
>>
>> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
>> index fe41c6a0fa67..697318019bd4 100644
>> --- a/tools/testing/selftests/kvm/Makefile
>> +++ b/tools/testing/selftests/kvm/Makefile
>> @@ -62,6 +62,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/tsc_msrs_test
>>   TEST_GEN_PROGS_x86_64 += demand_paging_test
>>   TEST_GEN_PROGS_x86_64 += dirty_log_test
>>   TEST_GEN_PROGS_x86_64 += dirty_log_perf_test
>> +TEST_GEN_PROGS_x86_64 += kvm_page_table_test
>>   TEST_GEN_PROGS_x86_64 += kvm_create_max_vcpus
>>   TEST_GEN_PROGS_x86_64 += set_memory_region_test
>>   TEST_GEN_PROGS_x86_64 += steal_time
>> @@ -71,6 +72,7 @@ TEST_GEN_PROGS_aarch64 += aarch64/get-reg-list-sve
>>   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_page_table_test
>>   TEST_GEN_PROGS_aarch64 += kvm_create_max_vcpus
>>   TEST_GEN_PROGS_aarch64 += set_memory_region_test
>>   TEST_GEN_PROGS_aarch64 += steal_time
>> @@ -80,6 +82,7 @@ TEST_GEN_PROGS_s390x += s390x/resets
>>   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_page_table_test
>>   TEST_GEN_PROGS_s390x += kvm_create_max_vcpus
>>   TEST_GEN_PROGS_s390x += set_memory_region_test
>>   
>> 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..b09c05288937
>> --- /dev/null
>> +++ b/tools/testing/selftests/kvm/kvm_page_table_test.c
>> @@ -0,0 +1,518 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * KVM page table test
>> + * Based on dirty_log_test.c
>> + * Based on dirty_log_perf_test.c
>> + *
>> + * Copyright (C) 2018, Red Hat, Inc.
>> + * Copyright (C) 2020, Google, Inc.
>> + * Copyright (C) 2021, Huawei, Inc.
> [Paolo's call but] I think we can drop 'based on .. ' and all but the
> last copyright notices as I don't quite see what value this gives. Yes,
> when a new test is implemented we use something else as a template but
> these are just tests after all.
Ok, I will remove it.
>> + *
>> + * Make sure that enough THP/HUGETLB pages have been allocated on systems
>> + * to cover the testing memory region before running this program, if you
>> + * wish to create block mappings in this test.
>> + */
>> +
>> +#define _GNU_SOURCE /* for program_invocation_name */
>> +
>> +#include <stdio.h>
>> +#include <stdlib.h>
>> +#include <time.h>
>> +#include <pthread.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
>> +
>> +/* Different memory accessing types for a vcpu */
>> +enum access_type {
>> +	ACCESS_TYPE_READ,
>> +	ACCESS_TYPE_WRITE,
>> +	NUM_ACCESS_TYPES,
>> +};
>> +
>> +/* Different memory accessing stages for a vcpu */
>> +enum test_stage {
>> +	KVM_CREATE_MAPPINGS,
>> +	KVM_UPDATE_MAPPINGS,
>> +	KVM_ADJUST_MAPPINGS,
>> +	KVM_BEFORE_MAPPINGS,
>> +	NUM_TEST_STAGES,
>> +};
>> +
>> +static const char * const access_type_string[] = {
>> +	"ACCESS_TYPE_READ ",
> 			^^^ extra space
>
>> +	"ACCESS_TYPE_WRITE",
>> +};
>> +
>> +static const char * const test_stage_string[] = {
>> +	"KVM_CREATE_MAPPINGS",
>> +	"KVM_UPDATE_MAPPINGS",
>> +	"KVM_ADJUST_MAPPINGS",
>> +	"KVM_BEFORE_MAPPINGS",
>> +};
>> +
> It would probably be possible to drop 'test_stage/access_type' enums and
> just use something like
>           for (i = 0; i < sizeof(test_stage_string); i++)
>                 ...
>
> for test stage and just a simple boolean for distinguishing read/write
> access.
I think the test_stage enums are still very useful because they have 
been used in many places
to make code easier to read. Besides, "enum guest_test_stage" also 
servers as a shared variable
between guest and host to let vcpu know which stage to execute.
And yes, it's more concise to drop access_type enums and strings, and 
use a simple boolean.
>> +struct perf_test_vcpu_args {
>> +	int vcpu_id;
>> +	enum access_type vcpu_access_type;
>> +};
>> +
>> +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 block_page_size;
>> +	uint64_t block_num_pages;
>> +	uint64_t host_pages_perblock;
>> +	enum vm_mem_backing_src_type backing_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 enum test_stage vcpu_last_completed_stage[KVM_MAX_VCPUS];
>> +static bool host_quit;
>> +
>> +/*
>> + * 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_vcpu_args *vcpu_args = &perf_test_args.vcpu_args[vcpu_id];
>> +	enum vm_mem_backing_src_type src_type = perf_test_args.backing_src_type;
>> +	uint64_t host_page_size = perf_test_args.host_page_size;
>> +	uint64_t host_num_pages = perf_test_args.host_num_pages;
>> +	uint64_t block_page_size = perf_test_args.block_page_size;
>> +	uint64_t block_num_pages = perf_test_args.block_num_pages;
>> +	uint64_t host_pages_perblock = perf_test_args.host_pages_perblock;
>> +	uint64_t half = host_pages_perblock / 2;
>> +	enum access_type vcpu_access_type;
>> +	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_access_type = vcpu_args->vcpu_access_type;
>> +
>> +	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 pages within the same memory range with different
>> +		 * and random access types(read or write). Then KVM will create
>> +		 * mappings for them (page mappings or block mappings).
>> +		 */
>> +		case KVM_CREATE_MAPPINGS:
>> +			for (i = 0; i < block_num_pages; i++) {
>> +				if (vcpu_access_type == ACCESS_TYPE_READ)
>> +					READ_ONCE(*(uint64_t *)addr);
>> +				else
>> +					*(uint64_t *)addr = 0x0123456789ABCDEF;
>> +
>> +				addr += block_page_size;
>> +			}
>> +			break;
>> +
>> +		/*
>> +		 * During dirty-logging, KVM will only update attributes of the
>> +		 * normal page mappings from RO to RW if backing source type is
>> +		 * anonymous, and will split the block mappings into normal page
>> +		 * mappings if backing source 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 < block_num_pages; i++) {
>> +				/* Write to the first host page of each block */
>> +				*(uint64_t *)addr = 0x0123456789ABCDEF;
>> +
>> +				/* Create half new page mappings for each block */
>> +				addr += host_page_size * half;
>> +				for (j = half; j < host_pages_perblock; 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 splitted
>> +		 * 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, &start);
> CLOCK_MONOTONIC_RAW maybe to avoid NTP corrections? (here and below)
Thanks, CLOCK_MONOTONIC is currently used in KVM selftests uniformly,
maybe we should replace them all with CLOCK_MONOTONIC_RAW.
>> +		ret = _vcpu_run(vm, vcpu_id);
>> +		ts_diff = timespec_diff_now(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);
>> +		vcpu_last_completed_stage[vcpu_id] = stage;
>> +		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);
>> +
>> +		while (stage == READ_ONCE(*current_stage) &&
>> +		       !READ_ONCE(host_quit)) {}
>> +	}
>> +
>> +	return NULL;
>> +}
>> +
>> +struct test_params {
>> +	enum vm_mem_backing_src_type backing_src_type;
>> +	uint64_t backing_src_granule;
>> +	uint64_t test_mem_size;
>> +	uint64_t phys_offset;
>> +};
>> +
>> +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;
>> +	uint64_t guest_page_size, guest_num_pages, host_page_size;
>> +	uint64_t block_page_size = p->backing_src_granule;
>> +	uint64_t test_mem_size = p->test_mem_size, test_num_pages;
>> +	void * host_test_mem;
>> +	struct kvm_vm *vm;
>> +	int vcpu_id;
>> +
>> +	guest_page_size = vm_guest_mode_params[mode].page_size;
>> +	host_page_size = getpagesize();
>> +
>> +	/*
>> +	 * Ensure that testing memory size is aligned to guest page size,
>> +	 * host page size and block page size, and that block page size
>> +	 * is aligned to host page size.
>> +	 */
>> +	TEST_ASSERT(test_mem_size % guest_page_size == 0,
>> +		    "Testing memory size is not guest page size aligned.");
>> +	TEST_ASSERT(test_mem_size % block_page_size  == 0,
>> +		    "Testing memory size is not block page size aligned.");
>> +	TEST_ASSERT(block_page_size % host_page_size == 0,
>> +		    "Block page size is not host page size aligned.");
>> +
>> +	guest_num_pages = test_mem_size / guest_page_size;
>> +	test_num_pages = test_mem_size / MIN_PAGE_SIZE;
>> +	vm = vm_create_with_vcpus(mode, nr_vcpus, test_num_pages, 0, guest_code, NULL);
>> +
>> +	if (!p->phys_offset) {
>> +		guest_test_phys_mem = (vm_get_max_gfn(vm) -
>> +				       guest_num_pages) * guest_page_size;
>> +		guest_test_phys_mem &= ~(block_page_size - 1);
>> +	} else {
>> +		guest_test_phys_mem = p->phys_offset;
>> +	}
>> +
>> +	/*
>> +	 * Ensure that guest physical offset of the testing memory slot is
>> +	 * block page size aligned, so that block mappings can be created
>> +	 * successfully by KVM.
>> +	 */
>> +	TEST_ASSERT(guest_test_phys_mem % block_page_size == 0,
>> +		    "Guest physical offset is not block page size aligned.");
>> +#ifdef __s390x__
>> +	/* Align to 1M (segment size) */
>> +	guest_test_phys_mem &= ~((1 << 20) - 1);
>> +#endif
>> +
>> +	/* 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.block_page_size = block_page_size;
>> +	perf_test_args.block_num_pages = test_mem_size / block_page_size;
>> +	perf_test_args.host_pages_perblock = block_page_size / host_page_size;
>> +	perf_test_args.backing_src_type = p->backing_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_access_type = random() % NUM_ACCESS_TYPES;
> I would've avoided using random here so that testing results are more
> stable. I.e. with a small number of vCPUs (say: 2) it may really make a
> difference if this will turn out being 'read'/'read' or
> 'read'/'write'. Would it be OK if we just do
>
>   vcpu_args->vcpu_access_type = vcpu_id % NUM_ACCESS_TYPES;
>
> instead?
It's a good suggestion.  What I want to implement here are different 
access types(read/write) to
the same page of concurrent vCPUs. So "vcpu_id % NUM_ACCESS_TYPES" does 
the same thing.
Maybe it's cleaner to just use "vcpu_id % NUM_ACCESS_TYPES" in 
guest_code(), and drop the
structure vcpu_args too.

Thanks,

Yanan.

>> +		pr_debug("Set access type of vCPU %d as %s\n",
>> +			 access_type_string[vcpu_args->vcpu_access_type]);
>> +
>> +		vcpu_last_completed_stage[vcpu_id] = NUM_TEST_STAGES;
>> +	}
>> +
>> +	/* Add an extra memory slot with specified backing source type */
>> +	vm_userspace_mem_region_add(vm, p->backing_src_type,
>> +				    guest_test_phys_mem,
>> +				    TEST_MEM_SLOT_INDEX,
>> +				    guest_num_pages, 0);
>> +
>> +	/* Do mapping 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);
>> +
>> +	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 backing source type: %s\n",
>> +		vm_mem_backing_src_type_string(p->backing_src_type));
>> +	pr_info("Testing backing source granule: 0x%lx\n", block_page_size);
>> +	pr_info("Testing memory size: 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;
>> +}
>> +
>> +static void run_test(enum vm_guest_mode mode, void *arg)
>> +{
>> +	pthread_t *vcpu_threads;
>> +	struct kvm_vm *vm;
>> +	int vcpu_id;
>> +	enum test_stage stage;
>> +	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;
>> +	stage = KVM_BEFORE_MAPPINGS;
>> +	*current_stage = stage;
>> +
>> +	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]);
>> +	}
>> +	for (vcpu_id = 0; vcpu_id < nr_vcpus; vcpu_id++) {
>> +		while (READ_ONCE(vcpu_last_completed_stage[vcpu_id]) != stage)
>> +			pr_debug("Waiting for vCPU %d to complete stage %s\n",
>> +				 vcpu_id, test_stage_string[stage]);
>> +	}
>> +	pr_info("Started all vCPUs successfully\n");
>> +
>> +	/* Test the stage of KVM creating mappings */
>> +	clock_gettime(CLOCK_MONOTONIC, &start);
>> +	stage = KVM_CREATE_MAPPINGS;
>> +	*current_stage = stage;
>> +
>> +	for (vcpu_id = 0; vcpu_id < nr_vcpus; vcpu_id++) {
>> +		while (READ_ONCE(vcpu_last_completed_stage[vcpu_id]) != stage)
>> +			pr_debug("Waiting for vCPU %d to complete stage %s\n",
>> +				 vcpu_id, test_stage_string[stage]);
>> +	}
>> +
>> +	ts_diff = timespec_diff_now(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);
>> +
>> +	clock_gettime(CLOCK_MONOTONIC, &start);
>> +	stage = KVM_UPDATE_MAPPINGS;
>> +	*current_stage = stage;
>> +
>> +	for (vcpu_id = 0; vcpu_id < nr_vcpus; vcpu_id++) {
>> +		while (READ_ONCE(vcpu_last_completed_stage[vcpu_id]) != stage)
>> +			pr_debug("Waiting for vCPU %d to complete stage %s\n",
>> +				 vcpu_id, test_stage_string[stage]);
>> +	}
>> +
>> +	ts_diff = timespec_diff_now(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);
>> +
>> +	clock_gettime(CLOCK_MONOTONIC, &start);
>> +	stage = KVM_ADJUST_MAPPINGS;
>> +	*current_stage = stage;
>> +
>> +	for (vcpu_id = 0; vcpu_id < nr_vcpus; vcpu_id++) {
>> +		while (READ_ONCE(vcpu_last_completed_stage[vcpu_id]) != stage)
>> +			pr_debug("Waiting for vCPU %d to complete stage %s\n",
>> +				 vcpu_id, test_stage_string[stage]);
>> +	}
>> +
>> +	ts_diff = timespec_diff_now(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;
>> +	for (vcpu_id = 0; vcpu_id < nr_vcpus; vcpu_id++)
>> +		pthread_join(vcpu_threads[vcpu_id], NULL);
>> +
>> +	free(vcpu_threads);
>> +	ucall_uninit(vm);
>> +	kvm_vm_free(vm);
>> +}
>> +
>> +static void vm_mem_backing_src_types_help(void)
>> +{
>> +	int i;
>> +
>> +	printf(" -t: specify backing source type of the testing memory region\n"
>> +	       "     (default: VM_MEM_SRC_ANONYMOUS)\n"
>> +	       "     Backing source type IDs:\n");
>> +
>> +	for (i = 0; i < NUM_VM_BACKING_SRC_TYPES; i++)
>> +		printf("         %d:    %s\n", i,  vm_mem_backing_src_type_string(i));
>> +}
>> +
>> +static void help(char *name)
>> +{
>> +	puts("");
>> +	printf("usage: %s [-h] [-m mode] [-t type] [-g granule] [-p offset] "
>> +	       "[-s size] [-v vcpus]\n", name);
>> +	puts("");
>> +	guest_modes_help();
>> +	vm_mem_backing_src_types_help();
>> +	printf(" -g: specify granule of the backing source pages. e.g. 2M or 1G.\n"
>> +	       "     (default: host page size)\n");
>> +	printf(" -p: specify guest physical test memory offset\n"
>> +	       "     must be aligned to granule of the backing source pages.\n"
>> +	       "     Warning: a low offset can conflict with the loaded test code.\n");
>> +	printf(" -s: specify size of the memory region for testing. e.g. 10M or 3G.\n"
>> +	       "     must be aligned to granule of the backing source pages.\n"
>> +	       "     (default: 1G)\n");
>> +	printf(" -v: specify the number of vCPUs to run\n"
>> +	       "     (default: 1)\n");
>> +	puts("");
>> +	exit(0);
>> +}
>> +
>> +int main(int argc, char *argv[])
>> +{
>> +	int max_vcpus = kvm_check_cap(KVM_CAP_MAX_VCPUS);
>> +	struct test_params p = {
>> +		.backing_src_type = VM_MEM_SRC_ANONYMOUS,
>> +		.backing_src_granule = getpagesize(),
>> +		.test_mem_size = DEFAULT_TEST_MEM_SIZE,
>> +	};
>> +	int opt, type;
>> +
>> +	guest_modes_append_default();
>> +
>> +	while ((opt = getopt(argc, argv, "hm:t:g:p:s:v:")) != -1) {
>> +		switch (opt) {
>> +		case 'm':
>> +			guest_modes_cmdline(optarg);
>> +			break;
>> +		case 't':
>> +			type = strtoul(optarg, NULL, 10);
>> +			TEST_ASSERT(type < NUM_VM_BACKING_SRC_TYPES,
>> +				    "Backing source type ID %d too big", type);
>> +			p.backing_src_type = type;
>> +			break;
>> +		case 'g':
>> +			p.backing_src_granule = parse_size(optarg);
>> +			break;
>> +		case 'p':
>> +			p.phys_offset = strtoull(optarg, NULL, 0);
>> +			break;
>> +		case 's':
>> +			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 'h':
>> +		default:
>> +			help(argv[0]);
>> +			break;
>> +		}
>> +	}
>> +
>> +	for_each_guest_mode(run_test, &p);
>> +
>> +	return 0;
>> +}