The demand paging test is currently a simple page access test which, while potentially useful, doesn't add much versus the existing dirty logging test. To improve the demand paging test, add a basic userfaultfd demand paging implementation.
Signed-off-by: Ben Gardon bgardon@google.com --- .../selftests/kvm/demand_paging_test.c | 196 +++++++++++++++++- 1 file changed, 192 insertions(+), 4 deletions(-)
diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c index 5f214517ba1de..6fab4468f97f6 100644 --- a/tools/testing/selftests/kvm/demand_paging_test.c +++ b/tools/testing/selftests/kvm/demand_paging_test.c @@ -11,11 +11,14 @@
#include <stdio.h> #include <stdlib.h> +#include <sys/syscall.h> #include <unistd.h> #include <time.h> +#include <poll.h> #include <pthread.h> #include <linux/bitmap.h> #include <linux/bitops.h> +#include <linux/userfaultfd.h>
#include "test_util.h" #include "kvm_util.h" @@ -39,6 +42,8 @@ static uint64_t host_page_size; static uint64_t guest_page_size; static uint64_t guest_num_pages;
+static char *guest_data_prototype; + /* * Guest physical memory offset of the testing memory slot. * This will be set to the topmost valid physical address minus @@ -110,13 +115,169 @@ static struct kvm_vm *create_vm(enum vm_guest_mode mode, uint32_t vcpuid, return vm; }
+static int handle_uffd_page_request(int uffd, uint64_t addr) +{ + pid_t tid; + struct uffdio_copy copy; + int r; + + tid = syscall(__NR_gettid); + + copy.src = (uint64_t)guest_data_prototype; + copy.dst = addr; + copy.len = host_page_size; + copy.mode = 0; + + r = ioctl(uffd, UFFDIO_COPY, ©); + if (r == -1) { + DEBUG("Failed Paged in 0x%lx from thread %d with errno: %d\n", + addr, tid, errno); + return r; + } + + return 0; +} + +bool quit_uffd_thread; + +struct uffd_handler_args { + int uffd; + int pipefd; +}; + +static void *uffd_handler_thread_fn(void *arg) +{ + struct uffd_handler_args *uffd_args = (struct uffd_handler_args *)arg; + int uffd = uffd_args->uffd; + int pipefd = uffd_args->pipefd; + int64_t pages = 0; + + while (!quit_uffd_thread) { + struct uffd_msg msg; + struct pollfd pollfd[2]; + char tmp_chr; + int r; + uint64_t addr; + + pollfd[0].fd = uffd; + pollfd[0].events = POLLIN; + pollfd[1].fd = pipefd; + pollfd[1].events = POLLIN; + + r = poll(pollfd, 2, -1); + switch (r) { + case -1: + DEBUG("poll err"); + continue; + case 0: + continue; + case 1: + break; + default: + DEBUG("Polling uffd returned %d", r); + return NULL; + } + + if (pollfd[0].revents & POLLERR) { + DEBUG("uffd revents has POLLERR"); + return NULL; + } + + if (pollfd[1].revents & POLLIN) { + r = read(pollfd[1].fd, &tmp_chr, 1); + TEST_ASSERT(r == 1, + "Error reading pipefd in UFFD thread\n"); + return NULL; + } + + if (!pollfd[0].revents & POLLIN) + continue; + + r = read(uffd, &msg, sizeof(msg)); + if (r == -1) { + if (errno == EAGAIN) + continue; + DEBUG("Read of uffd gor errno %d", errno); + return NULL; + } + + if (r != sizeof(msg)) { + DEBUG("Read on uffd returned unexpected size: %d bytes", + r); + return NULL; + } + + if (!(msg.event & UFFD_EVENT_PAGEFAULT)) + continue; + + addr = msg.arg.pagefault.address; + r = handle_uffd_page_request(uffd, addr); + if (r < 0) + return NULL; + pages++; + } + + return NULL; +} + +static int setup_demand_paging(struct kvm_vm *vm, + pthread_t *uffd_handler_thread, int pipefd) +{ + 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) { + DEBUG("uffd creation failed\n"); + return -1; + } + + uffdio_api.api = UFFD_API; + uffdio_api.features = 0; + if (ioctl(uffd, UFFDIO_API, &uffdio_api) == -1) { + DEBUG("ioctl uffdio_api failed\n"); + return -1; + } + + uffdio_register.range.start = (uint64_t)host_test_mem; + uffdio_register.range.len = host_num_pages * host_page_size; + uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING; + if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register) == -1) { + DEBUG("ioctl uffdio_register failed\n"); + return -1; + } + + if ((uffdio_register.ioctls & UFFD_API_RANGE_IOCTLS) != + UFFD_API_RANGE_IOCTLS) { + DEBUG("unexpected userfaultfd ioctl set\n"); + return -1; + } + + uffd_args.uffd = uffd; + uffd_args.pipefd = pipefd; + pthread_create(uffd_handler_thread, NULL, uffd_handler_thread_fn, + &uffd_args); + + return 0; +} + #define GUEST_MEM_SHIFT 30 /* 1G */ #define PAGE_SHIFT_4K 12
-static void run_test(enum vm_guest_mode mode) +static void run_test(enum vm_guest_mode mode, bool use_uffd) { pthread_t vcpu_thread; + pthread_t uffd_handler_thread; + int pipefd[2]; struct kvm_vm *vm; + int r;
/* * We reserve page table for 2 times of extra dirty mem which @@ -173,6 +334,16 @@ static void run_test(enum vm_guest_mode mode) /* Cache the HVA pointer of the region */ host_test_mem = addr_gpa2hva(vm, (vm_paddr_t)guest_test_phys_mem);
+ 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"); + + r = setup_demand_paging(vm, &uffd_handler_thread, pipefd[0]); + if (r < 0) + exit(-r); + } + #ifdef __x86_64__ vcpu_set_cpuid(vm, VCPU_ID, kvm_get_supported_cpuid()); #endif @@ -191,8 +362,20 @@ static void run_test(enum vm_guest_mode mode) /* Wait for the vcpu thread to quit */ pthread_join(vcpu_thread, NULL);
+ 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"); + + pthread_join(uffd_handler_thread, NULL); + } + ucall_uninit(vm); kvm_vm_free(vm); + + free(guest_data_prototype); }
struct vm_guest_mode_params { @@ -212,7 +395,7 @@ static void help(char *name) int i;
puts(""); - printf("usage: %s [-h] [-m mode]\n", name); + printf("usage: %s [-h] [-m mode] [-u]\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" @@ -221,6 +404,7 @@ static void help(char *name) printf(" %d: %s%s\n", i, vm_guest_mode_string(i), vm_guest_mode_params[i].supported ? " (supported)" : ""); } + printf(" -u: Use User Fault FD to handle vCPU page faults.\n"); puts(""); exit(0); } @@ -230,6 +414,7 @@ int main(int argc, char *argv[]) bool mode_selected = false; unsigned int mode; int opt, i; + bool use_uffd = false; #ifdef __aarch64__ unsigned int host_ipa_limit; #endif @@ -253,7 +438,7 @@ int main(int argc, char *argv[]) vm_guest_mode_params_init(VM_MODE_P40V48_4K, true, true); #endif
- while ((opt = getopt(argc, argv, "hm:")) != -1) { + while ((opt = getopt(argc, argv, "hm:u")) != -1) { switch (opt) { case 'm': if (!mode_selected) { @@ -266,6 +451,9 @@ int main(int argc, char *argv[]) "Guest mode ID %d too big", mode); vm_guest_mode_params[mode].enabled = true; break; + case 'u': + use_uffd = true; + break; case 'h': default: help(argv[0]); @@ -279,7 +467,7 @@ int main(int argc, char *argv[]) TEST_ASSERT(vm_guest_mode_params[i].supported, "Guest mode ID %d (%s) not supported.", i, vm_guest_mode_string(i)); - run_test(i); + run_test(i, use_uffd); }
return 0;