KVM: selftests: Support multiple vCPUs in demand paging test
authorBen Gardon <bgardon@google.com>
Thu, 23 Jan 2020 18:04:33 +0000 (10:04 -0800)
committerPaolo Bonzini <pbonzini@redhat.com>
Mon, 16 Mar 2020 16:57:05 +0000 (17:57 +0100)
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

index aa39d06..c516cec 100644 (file)
@@ -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
 
 #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;