Message-ID: <3d8d0fb9-b179-8a01-be1a-fa20f8a257ad@huawei.com>
Date:   Mon, 22 Mar 2021 19:59:04 +0800
From:   "wangyanan (Y)" <wangyanan55@...wei.com>
To:     Andrew Jones <drjones@...hat.com>
CC:     <kvm@...r.kernel.org>, <linux-kselftest@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "Ben Gardon" <bgardon@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>,
        "Vitaly Kuznetsov" <vkuznets@...hat.com>,
        Peter Xu <peterx@...hat.com>, Marc Zyngier <maz@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Jiri Olsa <jolsa@...hat.com>,
        "Arnaldo Carvalho de Melo" <acme@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        <wanghaibin.wang@...wei.com>, <yezengruan@...wei.com>,
        <yuzenghui@...wei.com>
Subject: Re: [RFC PATCH v4 9/9] KVM: selftests: Add a test for kvm page table
 code


On 2021/3/12 22:20, Andrew Jones wrote:
> On Tue, Mar 02, 2021 at 08:57:51PM +0800, 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@...wei.com>
>> Reviewed-by: Ben Gardon <bgardon@...gle.com>
>> ---
>>   tools/testing/selftests/kvm/Makefile          |   3 +
>>   .../selftests/kvm/kvm_page_table_test.c       | 476 ++++++++++++++++++
>>   2 files changed, 479 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 a6d61f451f88..bac81924166d 100644
>> --- a/tools/testing/selftests/kvm/Makefile
>> +++ b/tools/testing/selftests/kvm/Makefile
>> @@ -67,6 +67,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/xen_vmcall_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 += hardware_disable_test
>>   TEST_GEN_PROGS_x86_64 += kvm_create_max_vcpus
>>   TEST_GEN_PROGS_x86_64 += memslot_modification_stress_test
>> @@ -78,6 +79,7 @@ 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
>> @@ -87,6 +89,7 @@ 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
> Please add these three lines in alphabetic order. Also we're missing
> the .gitignore entry.
Will fix.
>>   
>> 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..032b49d1483b
>> --- /dev/null
>> +++ b/tools/testing/selftests/kvm/kvm_page_table_test.c
>> @@ -0,0 +1,476 @@
>> +// 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 "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
>> +
>> +/* Number of guest memory accessing types(read/write) */
>> +#define NUM_ACCESS_TYPES		2
> This define doesn't really seem necessary.
Agreed!
>> +
>> +/* 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 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.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 large_page_size = perf_test_args.large_page_size;
>> +	uint64_t large_num_pages = perf_test_args.large_num_pages;
>> +	uint64_t host_pages_per_lpage = perf_test_args.host_pages_per_lpage;
> Why not just create a short alias for perf_test_args, e.g. p, in order
> to access these more tersely?
Yes, it will be better, thanks!
>> +	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);
>> +		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)) {}
> Why busy wait instead of using some synchronization? E.g. sem_wait?
>
>> +	}
>> +
>> +	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 % NUM_ACCESS_TYPES);
> Why the '!'? Is this to ensure vcpu_id=0 is a writer? If so, why?
Whether to add '!' or not doesn't really matter when there are numerous 
vcpus,
but I prefer the vcpu to dirty the pages but not just reading when there 
is only
one vcpu configured. I think it's just a personal preference. :)
>> +
>> +		vcpu_last_completed_stage[vcpu_id] = NUM_TEST_STAGES;
>> +	}
>> +
>> +	/* 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);
>> +
>> +	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;
>> +}
>> +
>> +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]);
> I'd do a timed wait on some synchronization and then assert that it
> doesn't time out. At least the pr_debug() in the loop doesn't look
> like a good idea.
>
>> +	}
>> +	pr_info("Started all vCPUs successfully\n");
>> +
>> +	/* Test the stage of KVM creating mappings */
>> +	clock_gettime(CLOCK_MONOTONIC_RAW, &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_elapsed(start);
>> +	pr_info("KVM_CREATE_MAPPINGS: total execution time: %ld.%.9lds\n\n",
>> +		ts_diff.tv_sec, ts_diff.tv_nsec);
> Here the busy loop makes some sense for the time measuring. Alternatively
> we could still use sem_wait, but have the first vcpu to start record the
> start time and the last vcpu to finish record the end time. It might be
> nice to be able to see each individual vcpu's time too.
The sem_wait() way seems more reasonable than busy waiting, I will 
adjust the
corresponding parts in next version.

>> +
>> +	/* 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_RAW, &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_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);
>> +
>> +	clock_gettime(CLOCK_MONOTONIC_RAW, &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_elapsed(start);
>> +	pr_info("KVM_ADJUST_MAPPINGS: total execution time: %ld.%.9lds\n\n",
>> +		ts_diff.tv_sec, ts_diff.tv_nsec);
> Same comments for the last two loops as above about pr_debug and possibly
> using some synchronization. At least these loops, which are all the same,
> could be factored out into a function.
>
>> +
>> +	/* 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 help(char *name)
>> +{
>> +	puts("");
>> +	printf("usage: %s [-h] [-p offset] [-m mode] "
>> +	       "[-b mem size] [-v vcpus] [-s mem type]\n", name);
> Please hyphenate the parameter names: mem-size, mem-type
Of course.

Thanks for the above detailed suggestions,
Yanan
>> +	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;
>> +}
>> -- 
>> 2.23.0
>>
> Thanks,
> drew
>
> .

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