On Wed, May 19, 2021 at 2:04 PM James Houghton <jthoughton@xxxxxxxxxx> wrote: > > 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 +++++++++++++----- If you'd be willing to split this patch up into a few smaller patches, I'd find it much easier to review. Thank you for updating this test with your SIGBUS patch. > 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 >
