At the moment, demand_paging_test does not support profiling/testing multiple vCPU threads concurrently faulting on a single uffd because (a) "-u" (run test in userfaultfd mode) creates a uffd for each vCPU's region, so that each uffd services a single vCPU thread. (b) "-u -o" (userfaultfd mode + overlapped vCPU memory accesses) simply doesn't work: the test tries to register the same memory to multiple uffds, causing an error. Add support for many vcpus per uffd by (1) Keeping "-u" behavior unchanged. (2) Making "-u -a" create a single uffd for all of guest memory. (3) Making "-u -o" implicitly pass "-a", solving the problem in (b). In cases (2) and (3) all vCPU threads fault on a single uffd. With multiple potentially multiple vCPU per UFFD, it makes sense to allow configuring the number reader threads per UFFD as well: add the "-r" flag to do so. Signed-off-by: Anish Moorthy <amoorthy@xxxxxxxxxx> Acked-by: James Houghton <jthoughton@xxxxxxxxxx> --- .../selftests/kvm/aarch64/page_fault_test.c | 4 +- .../selftests/kvm/demand_paging_test.c | 62 +++++++++---- .../selftests/kvm/include/userfaultfd_util.h | 18 +++- .../selftests/kvm/lib/userfaultfd_util.c | 86 +++++++++++++------ 4 files changed, 125 insertions(+), 45 deletions(-) diff --git a/tools/testing/selftests/kvm/aarch64/page_fault_test.c b/tools/testing/selftests/kvm/aarch64/page_fault_test.c index df10f1ffa20d9..3b6d228a9340d 100644 --- a/tools/testing/selftests/kvm/aarch64/page_fault_test.c +++ b/tools/testing/selftests/kvm/aarch64/page_fault_test.c @@ -376,14 +376,14 @@ static void setup_uffd(struct kvm_vm *vm, struct test_params *p, *pt_uffd = uffd_setup_demand_paging(uffd_mode, 0, pt_args.hva, pt_args.paging_size, - test->uffd_pt_handler); + 1, test->uffd_pt_handler); *data_uffd = NULL; if (test->uffd_data_handler) *data_uffd = uffd_setup_demand_paging(uffd_mode, 0, data_args.hva, data_args.paging_size, - test->uffd_data_handler); + 1, test->uffd_data_handler); } static void free_uffd(struct test_desc *test, struct uffd_desc *pt_uffd, diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c index b0e1fc4de9e29..fc9c6ac76660c 100644 --- a/tools/testing/selftests/kvm/demand_paging_test.c +++ b/tools/testing/selftests/kvm/demand_paging_test.c @@ -58,7 +58,7 @@ static void vcpu_worker(struct memstress_vcpu_args *vcpu_args) } static int handle_uffd_page_request(int uffd_mode, int uffd, - struct uffd_msg *msg) + struct uffd_msg *msg) { pid_t tid = syscall(__NR_gettid); uint64_t addr = msg->arg.pagefault.address; @@ -77,8 +77,15 @@ static int handle_uffd_page_request(int uffd_mode, int uffd, copy.mode = 0; r = ioctl(uffd, UFFDIO_COPY, ©); - if (r == -1) { - pr_info("Failed UFFDIO_COPY in 0x%lx from thread %d with errno: %d\n", + /* + * With multiple vCPU threads fault on a single page and there are + * multiple readers for the UFFD, at least one of the UFFDIO_COPYs + * will fail with EEXIST: handle that case without signaling an + * error. + */ + if (r == -1 && errno != EEXIST) { + pr_info( + "Failed UFFDIO_COPY in 0x%lx from thread %d, errno = %d\n", addr, tid, errno); return r; } @@ -89,8 +96,10 @@ static int handle_uffd_page_request(int uffd_mode, int uffd, cont.range.len = demand_paging_size; r = ioctl(uffd, UFFDIO_CONTINUE, &cont); - if (r == -1) { - pr_info("Failed UFFDIO_CONTINUE in 0x%lx from thread %d with errno: %d\n", + /* See the note about EEXISTs in the UFFDIO_COPY branch. */ + if (r == -1 && errno != EEXIST) { + pr_info( + "Failed UFFDIO_CONTINUE in 0x%lx from thread %d, errno = %d\n", addr, tid, errno); return r; } @@ -110,7 +119,9 @@ static int handle_uffd_page_request(int uffd_mode, int uffd, struct test_params { int uffd_mode; + bool single_uffd; useconds_t uffd_delay; + int readers_per_uffd; enum vm_mem_backing_src_type src_type; bool partition_vcpu_memory_access; }; @@ -133,7 +144,8 @@ static void run_test(enum vm_guest_mode mode, void *arg) struct timespec start; struct timespec ts_diff; struct kvm_vm *vm; - int i; + int i, num_uffds = 0; + uint64_t uffd_region_size; vm = memstress_create_vm(mode, nr_vcpus, guest_percpu_mem_size, 1, p->src_type, p->partition_vcpu_memory_access); @@ -146,10 +158,13 @@ static void run_test(enum vm_guest_mode mode, void *arg) memset(guest_data_prototype, 0xAB, demand_paging_size); if (p->uffd_mode) { - uffd_descs = malloc(nr_vcpus * sizeof(struct uffd_desc *)); + num_uffds = p->single_uffd ? 1 : nr_vcpus; + uffd_region_size = nr_vcpus * guest_percpu_mem_size / num_uffds; + + uffd_descs = malloc(num_uffds * sizeof(struct uffd_desc *)); TEST_ASSERT(uffd_descs, "Memory allocation failed"); - for (i = 0; i < nr_vcpus; i++) { + for (i = 0; i < num_uffds; i++) { struct memstress_vcpu_args *vcpu_args; void *vcpu_hva; void *vcpu_alias; @@ -160,8 +175,7 @@ static void run_test(enum vm_guest_mode mode, void *arg) vcpu_hva = addr_gpa2hva(vm, vcpu_args->gpa); vcpu_alias = addr_gpa2alias(vm, vcpu_args->gpa); - prefault_mem(vcpu_alias, - vcpu_args->pages * memstress_args.guest_page_size); + prefault_mem(vcpu_alias, uffd_region_size); /* * Set up user fault fd to handle demand paging @@ -169,7 +183,8 @@ static void run_test(enum vm_guest_mode mode, void *arg) */ uffd_descs[i] = uffd_setup_demand_paging( p->uffd_mode, p->uffd_delay, vcpu_hva, - vcpu_args->pages * memstress_args.guest_page_size, + uffd_region_size, + p->readers_per_uffd, &handle_uffd_page_request); } } @@ -186,7 +201,7 @@ static void run_test(enum vm_guest_mode mode, void *arg) if (p->uffd_mode) { /* Tell the user fault fd handler threads to quit */ - for (i = 0; i < nr_vcpus; i++) + for (i = 0; i < num_uffds; i++) uffd_stop_demand_paging(uffd_descs[i]); } @@ -206,14 +221,19 @@ static void run_test(enum vm_guest_mode mode, void *arg) static void help(char *name) { puts(""); - printf("usage: %s [-h] [-m vm_mode] [-u uffd_mode] [-d uffd_delay_usec]\n" - " [-b memory] [-s type] [-v vcpus] [-o]\n", name); + printf("usage: %s [-h] [-m vm_mode] [-u uffd_mode] [-a]\n" + " [-d uffd_delay_usec] [-r readers_per_uffd] [-b memory]\n" + " [-s type] [-v vcpus] [-o]\n", name); guest_modes_help(); printf(" -u: use userfaultfd to handle vCPU page faults. Mode is a\n" " UFFD registration mode: 'MISSING' or 'MINOR'.\n"); + printf(" -a: Use a single userfaultfd for all of guest memory, instead of\n" + " creating one for each region paged by a unique vCPU\n" + " Set implicitly with -o, and no effect without -u.\n"); printf(" -d: add a delay in usec to the User Fault\n" " FD handler to simulate demand paging\n" " overheads. Ignored without -u.\n"); + printf(" -r: Set the number of reader threads per uffd.\n"); printf(" -b: specify the size of the memory region which should be\n" " demand paged by each vCPU. e.g. 10M or 3G.\n" " Default: 1G\n"); @@ -231,12 +251,14 @@ int main(int argc, char *argv[]) struct test_params p = { .src_type = DEFAULT_VM_MEM_SRC, .partition_vcpu_memory_access = true, + .readers_per_uffd = 1, + .single_uffd = false, }; int opt; guest_modes_append_default(); - while ((opt = getopt(argc, argv, "hm:u:d:b:s:v:o")) != -1) { + while ((opt = getopt(argc, argv, "ahom:u:d:b:s:v:r:")) != -1) { switch (opt) { case 'm': guest_modes_cmdline(optarg); @@ -248,6 +270,9 @@ int main(int argc, char *argv[]) p.uffd_mode = UFFDIO_REGISTER_MODE_MINOR; TEST_ASSERT(p.uffd_mode, "UFFD mode must be 'MISSING' or 'MINOR'."); break; + case 'a': + p.single_uffd = true; + break; case 'd': p.uffd_delay = strtoul(optarg, NULL, 0); TEST_ASSERT(p.uffd_delay >= 0, "A negative UFFD delay is not supported."); @@ -265,6 +290,13 @@ int main(int argc, char *argv[]) break; case 'o': p.partition_vcpu_memory_access = false; + p.single_uffd = true; + break; + case 'r': + p.readers_per_uffd = atoi(optarg); + TEST_ASSERT(p.readers_per_uffd >= 1, + "Invalid number of readers per uffd %d: must be >=1", + p.readers_per_uffd); break; case 'h': default: diff --git a/tools/testing/selftests/kvm/include/userfaultfd_util.h b/tools/testing/selftests/kvm/include/userfaultfd_util.h index 877449c345928..92cc1f9ec0686 100644 --- a/tools/testing/selftests/kvm/include/userfaultfd_util.h +++ b/tools/testing/selftests/kvm/include/userfaultfd_util.h @@ -17,18 +17,30 @@ typedef int (*uffd_handler_t)(int uffd_mode, int uffd, struct uffd_msg *msg); +struct uffd_reader_args { + int uffd_mode; + int uffd; + useconds_t delay; + uffd_handler_t handler; + /* Holds the read end of the pipe for killing the reader. */ + int pipe; +}; + struct uffd_desc { int uffd_mode; int uffd; - int pipefds[2]; useconds_t delay; uffd_handler_t handler; - pthread_t thread; + uint64_t num_readers; + /* Holds the write ends of the pipes for killing the readers. */ + int *pipefds; + pthread_t *readers; + struct uffd_reader_args *reader_args; }; struct uffd_desc *uffd_setup_demand_paging(int uffd_mode, useconds_t delay, void *hva, uint64_t len, - uffd_handler_t handler); + uint64_t num_readers, uffd_handler_t handler); void uffd_stop_demand_paging(struct uffd_desc *uffd); diff --git a/tools/testing/selftests/kvm/lib/userfaultfd_util.c b/tools/testing/selftests/kvm/lib/userfaultfd_util.c index 92cef20902f1f..2723ee1e3e1b2 100644 --- a/tools/testing/selftests/kvm/lib/userfaultfd_util.c +++ b/tools/testing/selftests/kvm/lib/userfaultfd_util.c @@ -27,10 +27,8 @@ static void *uffd_handler_thread_fn(void *arg) { - struct uffd_desc *uffd_desc = (struct uffd_desc *)arg; - int uffd = uffd_desc->uffd; - int pipefd = uffd_desc->pipefds[0]; - useconds_t delay = uffd_desc->delay; + struct uffd_reader_args *reader_args = (struct uffd_reader_args *)arg; + int uffd = reader_args->uffd; int64_t pages = 0; struct timespec start; struct timespec ts_diff; @@ -44,7 +42,7 @@ static void *uffd_handler_thread_fn(void *arg) pollfd[0].fd = uffd; pollfd[0].events = POLLIN; - pollfd[1].fd = pipefd; + pollfd[1].fd = reader_args->pipe; pollfd[1].events = POLLIN; r = poll(pollfd, 2, -1); @@ -92,9 +90,9 @@ static void *uffd_handler_thread_fn(void *arg) if (!(msg.event & UFFD_EVENT_PAGEFAULT)) continue; - if (delay) - usleep(delay); - r = uffd_desc->handler(uffd_desc->uffd_mode, uffd, &msg); + if (reader_args->delay) + usleep(reader_args->delay); + r = reader_args->handler(reader_args->uffd_mode, uffd, &msg); if (r < 0) return NULL; pages++; @@ -110,7 +108,7 @@ static void *uffd_handler_thread_fn(void *arg) struct uffd_desc *uffd_setup_demand_paging(int uffd_mode, useconds_t delay, void *hva, uint64_t len, - uffd_handler_t handler) + uint64_t num_readers, uffd_handler_t handler) { struct uffd_desc *uffd_desc; bool is_minor = (uffd_mode == UFFDIO_REGISTER_MODE_MINOR); @@ -118,14 +116,26 @@ struct uffd_desc *uffd_setup_demand_paging(int uffd_mode, useconds_t delay, struct uffdio_api uffdio_api; struct uffdio_register uffdio_register; uint64_t expected_ioctls = ((uint64_t) 1) << _UFFDIO_COPY; - int ret; + int ret, i; PER_PAGE_DEBUG("Userfaultfd %s mode, faults resolved with %s\n", is_minor ? "MINOR" : "MISSING", is_minor ? "UFFDIO_CONINUE" : "UFFDIO_COPY"); uffd_desc = malloc(sizeof(struct uffd_desc)); - TEST_ASSERT(uffd_desc, "malloc failed"); + TEST_ASSERT(uffd_desc, "Failed to malloc uffd descriptor"); + + uffd_desc->pipefds = malloc(sizeof(int) * num_readers); + TEST_ASSERT(uffd_desc->pipefds, "Failed to malloc pipes"); + + uffd_desc->readers = malloc(sizeof(pthread_t) * num_readers); + TEST_ASSERT(uffd_desc->readers, "Failed to malloc reader threads"); + + uffd_desc->reader_args = malloc( + sizeof(struct uffd_reader_args) * num_readers); + TEST_ASSERT(uffd_desc->reader_args, "Failed to malloc reader_args"); + + uffd_desc->num_readers = num_readers; /* In order to get minor faults, prefault via the alias. */ if (is_minor) @@ -148,18 +158,32 @@ struct uffd_desc *uffd_setup_demand_paging(int uffd_mode, useconds_t delay, TEST_ASSERT((uffdio_register.ioctls & expected_ioctls) == expected_ioctls, "missing userfaultfd ioctls"); - ret = pipe2(uffd_desc->pipefds, O_CLOEXEC | O_NONBLOCK); - TEST_ASSERT(!ret, "Failed to set up pipefd"); - uffd_desc->uffd_mode = uffd_mode; uffd_desc->uffd = uffd; uffd_desc->delay = delay; uffd_desc->handler = handler; - pthread_create(&uffd_desc->thread, NULL, uffd_handler_thread_fn, - uffd_desc); - PER_VCPU_DEBUG("Created uffd thread for HVA range [%p, %p)\n", - hva, hva + len); + for (i = 0; i < uffd_desc->num_readers; ++i) { + int pipes[2]; + + ret = pipe2((int *) &pipes, O_CLOEXEC | O_NONBLOCK); + TEST_ASSERT(!ret, "Failed to set up pipefd %i for uffd_desc %p", + i, uffd_desc); + + uffd_desc->pipefds[i] = pipes[1]; + + uffd_desc->reader_args[i].uffd_mode = uffd_mode; + uffd_desc->reader_args[i].uffd = uffd; + uffd_desc->reader_args[i].delay = delay; + uffd_desc->reader_args[i].handler = handler; + uffd_desc->reader_args[i].pipe = pipes[0]; + + pthread_create(&uffd_desc->readers[i], NULL, uffd_handler_thread_fn, + &uffd_desc->reader_args[i]); + + PER_VCPU_DEBUG("Created uffd thread %i for HVA range [%p, %p)\n", + i, hva, hva + len); + } return uffd_desc; } @@ -167,19 +191,31 @@ struct uffd_desc *uffd_setup_demand_paging(int uffd_mode, useconds_t delay, void uffd_stop_demand_paging(struct uffd_desc *uffd) { char c = 0; - int ret; + int i, ret; - ret = write(uffd->pipefds[1], &c, 1); - TEST_ASSERT(ret == 1, "Unable to write to pipefd"); + for (i = 0; i < uffd->num_readers; ++i) { + ret = write(uffd->pipefds[i], &c, 1); + TEST_ASSERT( + ret == 1, "Unable to write to pipefd %i for uffd_desc %p", i, uffd); + } - ret = pthread_join(uffd->thread, NULL); - TEST_ASSERT(ret == 0, "Pthread_join failed."); + for (i = 0; i < uffd->num_readers; ++i) { + ret = pthread_join(uffd->readers[i], NULL); + TEST_ASSERT( + ret == 0, + "Pthread_join failed on reader thread %i for uffd_desc %p", i, uffd); + } close(uffd->uffd); - close(uffd->pipefds[1]); - close(uffd->pipefds[0]); + for (i = 0; i < uffd->num_readers; ++i) { + close(uffd->pipefds[i]); + close(uffd->reader_args[i].pipe); + } + free(uffd->pipefds); + free(uffd->readers); + free(uffd->reader_args); free(uffd); } -- 2.40.0.rc1.284.g88254d51c5-goog