This exercises the KVM userfaultfd SIGBUS path to perform page-ins. This patch is based on Axel Rasmussen's patches that enable testing with HugeTLBFS: (https://lore.kernel.org/patchwork/patch/1432055/). This allows me to easily verify that the KVM patch does indeed work for anonymous, shmem-backed, and hugetlbfs-backed pages. Signed-off-by: James Houghton <jthoughton@xxxxxxxxxx> --- .../selftests/kvm/demand_paging_test.c | 193 +++++++++++++----- 1 file changed, 138 insertions(+), 55 deletions(-) diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c index 60d9b5223b9d..fe5f6fdf4b28 100644 --- a/tools/testing/selftests/kvm/demand_paging_test.c +++ b/tools/testing/selftests/kvm/demand_paging_test.c @@ -10,6 +10,7 @@ #define _GNU_SOURCE /* for pipe2 */ #include <inttypes.h> +#include <stdatomic.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> @@ -17,6 +18,7 @@ #include <poll.h> #include <pthread.h> #include <linux/userfaultfd.h> +#include <signal.h> #include <sys/syscall.h> #include "kvm_util.h" @@ -43,37 +45,25 @@ static uint64_t guest_percpu_mem_size = DEFAULT_PER_VCPU_MEM_SIZE; static size_t demand_paging_size; static char *guest_data_prototype; -static void *vcpu_worker(void *data) -{ - int ret; - struct perf_test_vcpu_args *vcpu_args = (struct perf_test_vcpu_args *)data; - int vcpu_id = vcpu_args->vcpu_id; - struct kvm_vm *vm = perf_test_args.vm; - struct kvm_run *run; - struct timespec start; - struct timespec ts_diff; - - vcpu_args_set(vm, vcpu_id, 1, vcpu_id); - run = vcpu_state(vm, vcpu_id); - - clock_gettime(CLOCK_MONOTONIC, &start); - - /* Let the guest access its memory */ - ret = _vcpu_run(vm, vcpu_id); - TEST_ASSERT(ret == 0, "vcpu_run failed: %d\n", ret); - if (get_ucall(vm, vcpu_id, NULL) != UCALL_SYNC) { - TEST_ASSERT(false, - "Invalid guest sync status: exit_reason=%s\n", - exit_reason_str(run->exit_reason)); - } +__thread uint64_t sigbus_address; +__thread atomic_bool sigbus_pending_fault; - ts_diff = timespec_elapsed(start); - PER_VCPU_DEBUG("vCPU %d execution time: %ld.%.9lds\n", vcpu_id, - ts_diff.tv_sec, ts_diff.tv_nsec); +static void handle_uffd_sigbus(int signum, siginfo_t *info, void *ctx) +{ + // Round down address. + uint64_t mask = ~(demand_paging_size - 1); - return NULL; + sigbus_address = (unsigned long long)(info->si_addr) & mask; + atomic_store_explicit(&sigbus_pending_fault, true, memory_order_release); } +struct vcpu_worker_args { + struct perf_test_vcpu_args *vcpu_args; + int uffd; + int uffd_mode; + bool use_uffd_sigbus; +}; + static int handle_uffd_page_request(int uffd_mode, int uffd, uint64_t addr) { pid_t tid = syscall(__NR_gettid); @@ -123,6 +113,53 @@ static int handle_uffd_page_request(int uffd_mode, int uffd, uint64_t addr) return 0; } +static void *vcpu_worker(void *data) +{ + int ret; + struct vcpu_worker_args *vcpu_worker_args = + (struct vcpu_worker_args *)data; + struct perf_test_vcpu_args *vcpu_args = vcpu_worker_args->vcpu_args; + int vcpu_id = vcpu_args->vcpu_id; + struct kvm_vm *vm = perf_test_args.vm; + struct kvm_run *run; + struct timespec start; + struct timespec ts_diff; + + vcpu_args_set(vm, vcpu_id, 1, vcpu_id); + run = vcpu_state(vm, vcpu_id); + + clock_gettime(CLOCK_MONOTONIC, &start); + + /* Let the guest access its memory */ + for (;;) { + ret = _vcpu_run(vm, vcpu_id); + if (vcpu_worker_args->use_uffd_sigbus && + atomic_load_explicit(&sigbus_pending_fault, + memory_order_acquire)) { + int r = handle_uffd_page_request( + vcpu_worker_args->uffd_mode, + vcpu_worker_args->uffd, sigbus_address); + TEST_ASSERT(r == 0, "handle_uffd_page_request failed"); + atomic_store_explicit(&sigbus_pending_fault, false, + memory_order_relaxed); + } else + break; + } + + TEST_ASSERT(ret == 0, "vcpu_run failed: %d\n", ret); + if (get_ucall(vm, vcpu_id, NULL) != UCALL_SYNC) { + TEST_ASSERT(false, + "Invalid guest sync status: exit_reason=%s\n", + exit_reason_str(run->exit_reason)); + } + + ts_diff = timespec_elapsed(start); + PER_VCPU_DEBUG("vCPU %d execution time: %ld.%.9lds\n", vcpu_id, + ts_diff.tv_sec, ts_diff.tv_nsec); + + return NULL; +} + bool quit_uffd_thread; struct uffd_handler_args { @@ -217,11 +254,8 @@ static void *uffd_handler_thread_fn(void *arg) return NULL; } -static void setup_demand_paging(struct kvm_vm *vm, - pthread_t *uffd_handler_thread, int pipefd, - int uffd_mode, useconds_t uffd_delay, - struct uffd_handler_args *uffd_args, - void *hva, void *alias, uint64_t len) +static int create_userfaultfd(int uffd_mode, bool use_uffd_sigbus, + void *hva, void *alias, uint64_t len) { bool is_minor = (uffd_mode == UFFDIO_REGISTER_MODE_MINOR); int uffd; @@ -250,7 +284,7 @@ static void setup_demand_paging(struct kvm_vm *vm, TEST_ASSERT(uffd >= 0, "uffd creation failed, errno: %d", errno); uffdio_api.api = UFFD_API; - uffdio_api.features = 0; + uffdio_api.features = use_uffd_sigbus ? UFFD_FEATURE_SIGBUS : 0; TEST_ASSERT(ioctl(uffd, UFFDIO_API, &uffdio_api) != -1, "ioctl UFFDIO_API failed: %" PRIu64, (uint64_t)uffdio_api.api); @@ -263,19 +297,29 @@ static void setup_demand_paging(struct kvm_vm *vm, TEST_ASSERT((uffdio_register.ioctls & expected_ioctls) == expected_ioctls, "missing userfaultfd ioctls"); + return uffd; +} + +static void start_uffd_thread(pthread_t *uffd_handler_thread, int *pipefds, + int uffd, int uffd_mode, useconds_t uffd_delay, + struct uffd_handler_args *uffd_args) +{ + int r; + + r = pipe2(pipefds, O_CLOEXEC | O_NONBLOCK); + TEST_ASSERT(!r, "Failed to set up pipefd"); + uffd_args->uffd_mode = uffd_mode; uffd_args->uffd = uffd; - uffd_args->pipefd = pipefd; + uffd_args->pipefd = pipefds[0]; uffd_args->delay = uffd_delay; pthread_create(uffd_handler_thread, NULL, uffd_handler_thread_fn, uffd_args); - - PER_VCPU_DEBUG("Created uffd thread for HVA range [%p, %p)\n", - hva, hva + len); } struct test_params { int uffd_mode; + bool use_uffd_sigbus; useconds_t uffd_delay; enum vm_mem_backing_src_type src_type; bool partition_vcpu_memory_access; @@ -286,6 +330,7 @@ static void run_test(enum vm_guest_mode mode, void *arg) struct test_params *p = arg; pthread_t *vcpu_threads; pthread_t *uffd_handler_threads = NULL; + struct vcpu_worker_args *vcpu_worker_args = NULL; struct uffd_handler_args *uffd_args = NULL; struct timespec start; struct timespec ts_diff; @@ -293,6 +338,7 @@ static void run_test(enum vm_guest_mode mode, void *arg) struct kvm_vm *vm; int vcpu_id; int r; + bool uffd_threads_needed; vm = perf_test_create_vm(mode, nr_vcpus, guest_percpu_mem_size, p->src_type); @@ -309,10 +355,16 @@ static void run_test(enum vm_guest_mode mode, void *arg) vcpu_threads = malloc(nr_vcpus * sizeof(*vcpu_threads)); TEST_ASSERT(vcpu_threads, "Memory allocation failed"); + vcpu_worker_args = malloc(nr_vcpus * sizeof(*vcpu_worker_args)); + TEST_ASSERT(vcpu_worker_args, "Memory allocation failed"); + perf_test_setup_vcpus(vm, nr_vcpus, guest_percpu_mem_size, p->partition_vcpu_memory_access); - if (p->uffd_mode) { + uffd_threads_needed = p->uffd_mode && !p->use_uffd_sigbus; + if (uffd_threads_needed) { + // Handler threads are not necessary when using + // UFFD_FEATURE_SIGBUS. uffd_handler_threads = malloc(nr_vcpus * sizeof(*uffd_handler_threads)); TEST_ASSERT(uffd_handler_threads, "Memory allocation failed"); @@ -322,6 +374,21 @@ static void run_test(enum vm_guest_mode mode, void *arg) pipefds = malloc(sizeof(int) * nr_vcpus * 2); TEST_ASSERT(pipefds, "Unable to allocate memory for pipefd"); + } + + if (p->use_uffd_sigbus) { + struct sigaction action; + + memset(&action, 0, sizeof(action)); + action.sa_sigaction = handle_uffd_sigbus; + action.sa_flags = SA_SIGINFO; + if (sigaction(SIGBUS, &action, NULL) < 0) { + perror("Failed to set sigaction"); + return; + } + } + + if (p->uffd_mode) { for (vcpu_id = 0; vcpu_id < nr_vcpus; vcpu_id++) { vm_paddr_t vcpu_gpa; @@ -329,7 +396,6 @@ static void run_test(enum vm_guest_mode mode, void *arg) void *vcpu_alias; uint64_t vcpu_mem_size; - if (p->partition_vcpu_memory_access) { vcpu_gpa = guest_test_phys_mem + (vcpu_id * guest_percpu_mem_size); @@ -339,7 +405,8 @@ static void run_test(enum vm_guest_mode mode, void *arg) vcpu_mem_size = guest_percpu_mem_size * nr_vcpus; } PER_VCPU_DEBUG("Added VCPU %d with test mem gpa [%lx, %lx)\n", - vcpu_id, vcpu_gpa, vcpu_gpa + vcpu_mem_size); + vcpu_id, vcpu_gpa, + vcpu_gpa + vcpu_mem_size); /* Cache the host addresses of the region */ vcpu_hva = addr_gpa2hva(vm, vcpu_gpa); @@ -349,28 +416,39 @@ static void run_test(enum vm_guest_mode mode, void *arg) * 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"); - - setup_demand_paging(vm, &uffd_handler_threads[vcpu_id], - pipefds[vcpu_id * 2], p->uffd_mode, - p->uffd_delay, &uffd_args[vcpu_id], - vcpu_hva, vcpu_alias, - vcpu_mem_size); + r = create_userfaultfd(p->uffd_mode, p->use_uffd_sigbus, + vcpu_hva, vcpu_alias, + vcpu_mem_size); + if (r < 0) + exit(-r); + + if (uffd_threads_needed) { + start_uffd_thread(&uffd_handler_threads[vcpu_id], + &pipefds[vcpu_id * 2], + r, p->uffd_mode, p->uffd_delay, + &uffd_args[vcpu_id]); + PER_VCPU_DEBUG("Created uffd thread for HVA range [%p, %p)\n", + vcpu_hva, vcpu_hva + vcpu_mem_size); + } + + vcpu_worker_args[vcpu_id].uffd = r; } } /* Export the shared variables to the guest */ sync_global_to_guest(vm, perf_test_args); - pr_info("Finished creating vCPUs and starting uffd threads\n"); + pr_info("Finished creating vCPUs\n"); clock_gettime(CLOCK_MONOTONIC, &start); for (vcpu_id = 0; vcpu_id < nr_vcpus; vcpu_id++) { + vcpu_worker_args[vcpu_id].vcpu_args = + &perf_test_args.vcpu_args[vcpu_id]; + vcpu_worker_args[vcpu_id].use_uffd_sigbus = p->use_uffd_sigbus; + vcpu_worker_args[vcpu_id].uffd_mode = p->uffd_mode; pthread_create(&vcpu_threads[vcpu_id], NULL, vcpu_worker, - &perf_test_args.vcpu_args[vcpu_id]); + &vcpu_worker_args[vcpu_id]); } pr_info("Started all vCPUs\n"); @@ -385,7 +463,7 @@ static void run_test(enum vm_guest_mode mode, void *arg) pr_info("All vCPU threads joined\n"); - if (p->uffd_mode) { + if (uffd_threads_needed) { char c; /* Tell the user fault fd handler threads to quit */ @@ -407,7 +485,8 @@ static void run_test(enum vm_guest_mode mode, void *arg) free(guest_data_prototype); free(vcpu_threads); - if (p->uffd_mode) { + free(vcpu_worker_args); + if (uffd_threads_needed) { free(uffd_handler_threads); free(uffd_args); free(pipefds); @@ -417,11 +496,12 @@ static void run_test(enum vm_guest_mode mode, void *arg) static void help(char *name) { puts(""); - printf("usage: %s [-h] [-m mode] [-u mode] [-d uffd_delay_usec]\n" + printf("usage: %s [-h] [-m mode] [-u mode] [-s] [-d uffd_delay_usec]\n" " [-b memory] [-t 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(" -s: use UFFD_FEATURE_SIGBUS to perform page-ins.\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"); @@ -448,7 +528,7 @@ int main(int argc, char *argv[]) guest_modes_append_default(); - while ((opt = getopt(argc, argv, "hm:u:d:b:t:v:o")) != -1) { + while ((opt = getopt(argc, argv, "hm:u:sd:b:t:v:o")) != -1) { switch (opt) { case 'm': guest_modes_cmdline(optarg); @@ -460,6 +540,9 @@ 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 's': + p.use_uffd_sigbus = true; + break; case 'd': p.uffd_delay = strtoul(optarg, NULL, 0); TEST_ASSERT(p.uffd_delay >= 0, "A negative UFFD delay is not supported."); -- 2.31.1.751.gd2f1c929bd-goog
