KVM: selftests: Support multiple vCPUs in demand paging test

Most VMs have multiple vCPUs, the concurrent execution of which has a
substantial impact on demand paging performance. Add an option to create
multiple vCPUs to each access disjoint regions of memory.
Signed-off-by: Ben Gardon <bgardon@google.com>
[guest_code() can't return, use GUEST_ASSERT(). Ensure the number
 of guests pages is compatible with the host.]
Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/demand_paging_test.c

@@ -26,7 +26,6 @@
 #include "processor.h"
 
 #ifdef __NR_userfaultfd
-#define VCPU_ID				1
 
 /* The memory slot index demand page */
 #define TEST_MEM_SLOT_INDEX		1
@@ -36,6 +35,14 @@
 
 #define DEFAULT_GUEST_TEST_MEM_SIZE (1 << 30) /* 1G */
 
+#ifdef PRINT_PER_VCPU_UPDATES
+#define PER_VCPU_DEBUG(...) DEBUG(__VA_ARGS__)
+#else
+#define PER_VCPU_DEBUG(...)
+#endif
+
+#define MAX_VCPUS 512
+
 /*
  * Guest/Host shared variables. Ensure addr_gva2hva() and/or
  * sync_global_to/from_guest() are used when accessing from
@@ -69,18 +76,24 @@ struct vcpu_args {
 	struct kvm_vm *vm;
 };
 
-static struct vcpu_args vcpu_args;
+static struct vcpu_args vcpu_args[MAX_VCPUS];
 
 /*
  * Continuously write to the first 8 bytes of each page in the demand paging
  * memory region.
  */
-static void guest_code(void)
+static void guest_code(uint32_t vcpu_id)
 {
-	uint64_t gva = vcpu_args.gva;
-	uint64_t pages = vcpu_args.pages;
+	uint64_t gva;
+	uint64_t pages;
 	int i;
 
+	/* Make sure vCPU args data structure is not corrupt. */
+	GUEST_ASSERT(vcpu_args[vcpu_id].vcpu_id == vcpu_id);
+
+	gva = vcpu_args[vcpu_id].gva;
+	pages = vcpu_args[vcpu_id].pages;
+
 	for (i = 0; i < pages; i++) {
 		uint64_t addr = gva + (i * guest_page_size);
 
@@ -91,17 +104,15 @@ static void guest_code(void)
 	GUEST_SYNC(1);
 }
 
-/* Points to the test VM memory region on which we are doing demand paging */
-static void *host_test_mem;
-static uint64_t host_num_pages;
-
 static void *vcpu_worker(void *data)
 {
 	int ret;
-	struct kvm_vm *vm = vcpu_args.vm;
-	int vcpu_id = vcpu_args.vcpu_id;
+	struct vcpu_args *args = (struct vcpu_args *)data;
+	struct kvm_vm *vm = args->vm;
+	int vcpu_id = args->vcpu_id;
 	struct kvm_run *run;
 
+	vcpu_args_set(vm, vcpu_id, 1, vcpu_id);
 	run = vcpu_state(vm, vcpu_id);
 
 	/* Let the guest access its memory */
@@ -116,18 +127,34 @@ static void *vcpu_worker(void *data)
 	return NULL;
 }
 
-static struct kvm_vm *create_vm(enum vm_guest_mode mode, uint32_t vcpuid,
-				uint64_t extra_mem_pages, void *guest_code)
+#define PAGE_SHIFT_4K  12
+#define PTES_PER_4K_PT 512
+
+static struct kvm_vm *create_vm(enum vm_guest_mode mode, int vcpus,
+				uint64_t vcpu_memory_bytes)
 {
 	struct kvm_vm *vm;
-	uint64_t extra_pg_pages = extra_mem_pages / 512 * 2;
+	uint64_t pages = DEFAULT_GUEST_PHY_PAGES;
+
+	/* Account for a few pages per-vCPU for stacks */
+	pages += DEFAULT_STACK_PGS * vcpus;
+
+	/*
+	 * Reserve twice the ammount of memory needed to map the test region and
+	 * the page table / stacks region, at 4k, for page tables. Do the
+	 * calculation with 4K page size: the smallest of all archs. (e.g., 64K
+	 * page size guest will need even less memory for page tables).
+	 */
+	pages += (2 * pages) / PTES_PER_4K_PT;
+	pages += ((2 * vcpus * vcpu_memory_bytes) >> PAGE_SHIFT_4K) /
+		 PTES_PER_4K_PT;
+	pages = vm_adjust_num_guest_pages(mode, pages);
 
-	vm = _vm_create(mode, DEFAULT_GUEST_PHY_PAGES + extra_pg_pages, O_RDWR);
+	vm = _vm_create(mode, pages, O_RDWR);
 	kvm_vm_elf_load(vm, program_invocation_name, 0, 0);
 #ifdef __x86_64__
 	vm_create_irqchip(vm);
 #endif
-	vm_vcpu_add_default(vm, vcpuid, guest_code);
 	return vm;
 }
 
@@ -242,17 +269,13 @@ static void *uffd_handler_thread_fn(void *arg)
 
 static int setup_demand_paging(struct kvm_vm *vm,
 			       pthread_t *uffd_handler_thread, int pipefd,
-			       useconds_t uffd_delay)
+			       useconds_t uffd_delay,
+			       struct uffd_handler_args *uffd_args,
+			       void *hva, uint64_t len)
 {
 	int uffd;
 	struct uffdio_api uffdio_api;
 	struct uffdio_register uffdio_register;
-	struct uffd_handler_args uffd_args;
-
-	guest_data_prototype = malloc(host_page_size);
-	TEST_ASSERT(guest_data_prototype,
-		    "Failed to allocate buffer for guest data pattern");
-	memset(guest_data_prototype, 0xAB, host_page_size);
 
 	uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
 	if (uffd == -1) {
@@ -267,8 +290,8 @@ static int setup_demand_paging(struct kvm_vm *vm,
 		return -1;
 	}
 
-	uffdio_register.range.start = (uint64_t)host_test_mem;
-	uffdio_register.range.len = host_num_pages * host_page_size;
+	uffdio_register.range.start = (uint64_t)hva;
+	uffdio_register.range.len = len;
 	uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
 	if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register) == -1) {
 		DEBUG("ioctl uffdio_register failed\n");
@@ -281,44 +304,40 @@ static int setup_demand_paging(struct kvm_vm *vm,
 		return -1;
 	}
 
-	uffd_args.uffd = uffd;
-	uffd_args.pipefd = pipefd;
-	uffd_args.delay = uffd_delay;
+	uffd_args->uffd = uffd;
+	uffd_args->pipefd = pipefd;
+	uffd_args->delay = uffd_delay;
 	pthread_create(uffd_handler_thread, NULL, uffd_handler_thread_fn,
-		       &uffd_args);
+		       uffd_args);
+
+	PER_VCPU_DEBUG("Created uffd thread for HVA range [%p, %p)\n",
+		       hva, hva + len);
 
 	return 0;
 }
 
-#define PAGE_SHIFT_4K  12
-
 static void run_test(enum vm_guest_mode mode, bool use_uffd,
-		     useconds_t uffd_delay, uint64_t guest_memory_bytes)
+		     useconds_t uffd_delay, int vcpus,
+		     uint64_t vcpu_memory_bytes)
 {
-	pthread_t vcpu_thread;
-	pthread_t uffd_handler_thread;
-	int pipefd[2];
+	pthread_t *vcpu_threads;
+	pthread_t *uffd_handler_threads = NULL;
+	struct uffd_handler_args *uffd_args = NULL;
+	int *pipefds = NULL;
 	struct kvm_vm *vm;
 	uint64_t guest_num_pages;
+	int vcpu_id;
 	int r;
 
-	/*
-	 * We reserve page table for twice the ammount of memory we intend
-	 * to use in the test region for demand paging. Here we do the
-	 * calculation with 4K page size which is the smallest so the page
-	 * number will be enough for all archs. (e.g., 64K page size guest
-	 * will need even less memory for page tables).
-	 */
-	vm = create_vm(mode, VCPU_ID,
-		       (2 * guest_memory_bytes) >> PAGE_SHIFT_4K,
-		       guest_code);
+	vm = create_vm(mode, vcpus, vcpu_memory_bytes);
 
 	guest_page_size = vm_get_page_size(vm);
 
-	TEST_ASSERT(guest_memory_bytes % guest_page_size == 0,
+	TEST_ASSERT(vcpu_memory_bytes % guest_page_size == 0,
 		    "Guest memory size is not guest page size aligned.");
 
-	guest_num_pages = guest_memory_bytes / guest_page_size;
+	guest_num_pages = (vcpus * vcpu_memory_bytes) / guest_page_size;
+	guest_num_pages = vm_adjust_num_guest_pages(mode, guest_num_pages);
 
 #ifdef __s390x__
 	/* Round up to multiple of 1M (segment size) */
@@ -330,13 +349,13 @@ static void run_test(enum vm_guest_mode mode, bool use_uffd,
 	 */
 	TEST_ASSERT(guest_num_pages < vm_get_max_gfn(vm),
 		    "Requested more guest memory than address space allows.\n"
-		    "    guest pages: %lx max gfn: %lx\n",
-		    guest_num_pages, vm_get_max_gfn(vm));
+		    "    guest pages: %lx max gfn: %lx vcpus: %d wss: %lx]\n",
+		    guest_num_pages, vm_get_max_gfn(vm), vcpus,
+		    vcpu_memory_bytes);
 
 	host_page_size = getpagesize();
-	TEST_ASSERT(guest_memory_bytes % host_page_size == 0,
+	TEST_ASSERT(vcpu_memory_bytes % host_page_size == 0,
 		    "Guest memory size is not host page size aligned.");
-	host_num_pages = guest_memory_bytes / host_page_size;
 
 	guest_test_phys_mem = (vm_get_max_gfn(vm) - guest_num_pages) *
 			      guest_page_size;
@@ -361,55 +380,114 @@ static void run_test(enum vm_guest_mode mode, bool use_uffd,
 	virt_map(vm, guest_test_virt_mem, guest_test_phys_mem,
 		 guest_num_pages * guest_page_size, 0);
 
-	/* Cache the HVA pointer of the region */
-	host_test_mem = addr_gpa2hva(vm, (vm_paddr_t)guest_test_phys_mem);
+	ucall_init(vm, NULL);
+
+	guest_data_prototype = malloc(host_page_size);
+	TEST_ASSERT(guest_data_prototype,
+		    "Failed to allocate buffer for guest data pattern");
+	memset(guest_data_prototype, 0xAB, host_page_size);
+
+	vcpu_threads = malloc(vcpus * sizeof(*vcpu_threads));
+	TEST_ASSERT(vcpu_threads, "Memory allocation failed");
 
 	if (use_uffd) {
-		/* Set up user fault fd to handle demand paging requests. */
-		r = pipe2(pipefd, O_CLOEXEC | O_NONBLOCK);
-		TEST_ASSERT(!r, "Failed to set up pipefd");
+		uffd_handler_threads =
+			malloc(vcpus * sizeof(*uffd_handler_threads));
+		TEST_ASSERT(uffd_handler_threads, "Memory allocation failed");
 
-		r = setup_demand_paging(vm, &uffd_handler_thread, pipefd[0],
-					uffd_delay);
-		if (r < 0)
-			exit(-r);
+		uffd_args = malloc(vcpus * sizeof(*uffd_args));
+		TEST_ASSERT(uffd_args, "Memory allocation failed");
+
+		pipefds = malloc(sizeof(int) * vcpus * 2);
+		TEST_ASSERT(pipefds, "Unable to allocate memory for pipefd");
 	}
 
+	for (vcpu_id = 0; vcpu_id < vcpus; vcpu_id++) {
+		vm_paddr_t vcpu_gpa;
+		void *vcpu_hva;
+
+		vm_vcpu_add_default(vm, vcpu_id, guest_code);
+
+		vcpu_gpa = guest_test_phys_mem + (vcpu_id * vcpu_memory_bytes);
+		PER_VCPU_DEBUG("Added VCPU %d with test mem gpa [%lx, %lx)\n",
+			       vcpu_id, vcpu_gpa, vcpu_gpa + vcpu_memory_bytes);
+
+		/* Cache the HVA pointer of the region */
+		vcpu_hva = addr_gpa2hva(vm, vcpu_gpa);
+
+		if (use_uffd) {
+			/*
+			 * Set up user fault fd to handle demand paging
+			 * requests.
+			 */
+			r = pipe2(&pipefds[vcpu_id * 2],
+				  O_CLOEXEC | O_NONBLOCK);
+			TEST_ASSERT(!r, "Failed to set up pipefd");
+
+			r = setup_demand_paging(vm,
+						&uffd_handler_threads[vcpu_id],
+						pipefds[vcpu_id * 2],
+						uffd_delay, &uffd_args[vcpu_id],
+						vcpu_hva, vcpu_memory_bytes);
+			if (r < 0)
+				exit(-r);
+		}
+
 #ifdef __x86_64__
-	vcpu_set_cpuid(vm, VCPU_ID, kvm_get_supported_cpuid());
-#endif
-#ifdef __aarch64__
-	ucall_init(vm, NULL);
+		vcpu_set_cpuid(vm, vcpu_id, kvm_get_supported_cpuid());
 #endif
 
+		vcpu_args[vcpu_id].vm = vm;
+		vcpu_args[vcpu_id].vcpu_id = vcpu_id;
+		vcpu_args[vcpu_id].gva = guest_test_virt_mem +
+					 (vcpu_id * vcpu_memory_bytes);
+		vcpu_args[vcpu_id].pages = vcpu_memory_bytes / guest_page_size;
+	}
+
 	/* Export the shared variables to the guest */
 	sync_global_to_guest(vm, host_page_size);
 	sync_global_to_guest(vm, guest_page_size);
-
-	vcpu_args.vm = vm;
-	vcpu_args.vcpu_id = VCPU_ID;
-	vcpu_args.gva = guest_test_virt_mem;
-	vcpu_args.pages = guest_num_pages;
 	sync_global_to_guest(vm, vcpu_args);
-	pthread_create(&vcpu_thread, NULL, vcpu_worker, &vcpu_args);
 
-	/* Wait for the vcpu thread to quit */
-	pthread_join(vcpu_thread, NULL);
+	DEBUG("Finished creating vCPUs and starting uffd threads\n");
+
+	for (vcpu_id = 0; vcpu_id < vcpus; vcpu_id++) {
+		pthread_create(&vcpu_threads[vcpu_id], NULL, vcpu_worker,
+			       &vcpu_args[vcpu_id]);
+	}
+
+	DEBUG("Started all vCPUs\n");
+
+	/* Wait for the vcpu threads to quit */
+	for (vcpu_id = 0; vcpu_id < vcpus; vcpu_id++) {
+		pthread_join(vcpu_threads[vcpu_id], NULL);
+		PER_VCPU_DEBUG("Joined thread for vCPU %d\n", vcpu_id);
+	}
+
+	DEBUG("All vCPU threads joined\n");
 
 	if (use_uffd) {
 		char c;
 
-		/* Tell the user fault fd handler thread to quit */
-		r = write(pipefd[1], &c, 1);
-		TEST_ASSERT(r == 1, "Unable to write to pipefd");
+		/* Tell the user fault fd handler threads to quit */
+		for (vcpu_id = 0; vcpu_id < vcpus; vcpu_id++) {
+			r = write(pipefds[vcpu_id * 2 + 1], &c, 1);
+			TEST_ASSERT(r == 1, "Unable to write to pipefd");
 
-		pthread_join(uffd_handler_thread, NULL);
+			pthread_join(uffd_handler_threads[vcpu_id], NULL);
+		}
 	}
 
 	ucall_uninit(vm);
 	kvm_vm_free(vm);
 
 	free(guest_data_prototype);
+	free(vcpu_threads);
+	if (use_uffd) {
+		free(uffd_handler_threads);
+		free(uffd_args);
+		free(pipefds);
+	}
 }
 
 struct guest_mode {
@@ -428,7 +506,7 @@ static void help(char *name)
 
 	puts("");
 	printf("usage: %s [-h] [-m mode] [-u] [-d uffd_delay_usec]\n"
-	       "          [-b memory]\n", name);
+	       "          [-b memory] [-v vcpus]\n", name);
 	printf(" -m: specify the guest mode ID to test\n"
 	       "     (default: test all supported modes)\n"
 	       "     This option may be used multiple times.\n"
@@ -443,7 +521,9 @@ static void help(char *name)
 	       "     FD handler to simulate demand paging\n"
 	       "     overheads. Ignored without -u.\n");
 	printf(" -b: specify the size of the memory region which should be\n"
-	       "     demand paged. e.g. 10M or 3G. Default: 1G\n");
+	       "     demand paged by each vCPU. e.g. 10M or 3G.\n"
+	       "     Default: 1G\n");
+	printf(" -v: specify the number of vCPUs to run.\n");
 	puts("");
 	exit(0);
 }
@@ -451,7 +531,8 @@ static void help(char *name)
 int main(int argc, char *argv[])
 {
 	bool mode_selected = false;
-	uint64_t guest_memory_bytes = DEFAULT_GUEST_TEST_MEM_SIZE;
+	uint64_t vcpu_memory_bytes = DEFAULT_GUEST_TEST_MEM_SIZE;
+	int vcpus = 1;
 	unsigned int mode;
 	int opt, i;
 	bool use_uffd = false;
@@ -478,7 +559,7 @@ int main(int argc, char *argv[])
 	guest_mode_init(VM_MODE_P40V48_4K, true, true);
 #endif
 
-	while ((opt = getopt(argc, argv, "hm:ud:b:")) != -1) {
+	while ((opt = getopt(argc, argv, "hm:ud:b:v:")) != -1) {
 		switch (opt) {
 		case 'm':
 			if (!mode_selected) {
@@ -500,7 +581,15 @@ int main(int argc, char *argv[])
 				    "A negative UFFD delay is not supported.");
 			break;
 		case 'b':
-			guest_memory_bytes = parse_size(optarg);
+			vcpu_memory_bytes = parse_size(optarg);
+			break;
+		case 'v':
+			vcpus = atoi(optarg);
+			TEST_ASSERT(vcpus > 0,
+				    "Must have a positive number of vCPUs");
+			TEST_ASSERT(vcpus <= MAX_VCPUS,
+				    "This test does not currently support\n"
+				    "more than %d vCPUs.", MAX_VCPUS);
 			break;
 		case 'h':
 		default:
@@ -515,7 +604,7 @@ int main(int argc, char *argv[])
 		TEST_ASSERT(guest_modes[i].supported,
 			    "Guest mode ID %d (%s) not supported.",
 			    i, vm_guest_mode_string(i));
-		run_test(i, use_uffd, uffd_delay, guest_memory_bytes);
+		run_test(i, use_uffd, uffd_delay, vcpus, vcpu_memory_bytes);
 	}
 
 	return 0;