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-rw-r--r--tools/testing/selftests/kvm/demand_paging_test.c360
1 files changed, 360 insertions, 0 deletions
diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c
new file mode 100644
index 000000000000..0202b78f8680
--- /dev/null
+++ b/tools/testing/selftests/kvm/demand_paging_test.c
@@ -0,0 +1,360 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KVM demand paging test
+ * Adapted from dirty_log_test.c
+ *
+ * Copyright (C) 2018, Red Hat, Inc.
+ * Copyright (C) 2019, Google, Inc.
+ */
+#include <inttypes.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <pthread.h>
+#include <linux/userfaultfd.h>
+#include <sys/syscall.h>
+
+#include "kvm_util.h"
+#include "test_util.h"
+#include "memstress.h"
+#include "guest_modes.h"
+#include "ucall_common.h"
+#include "userfaultfd_util.h"
+
+#ifdef __NR_userfaultfd
+
+static int nr_vcpus = 1;
+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(struct memstress_vcpu_args *vcpu_args)
+{
+ struct kvm_vcpu *vcpu = vcpu_args->vcpu;
+ int vcpu_idx = vcpu_args->vcpu_idx;
+ struct kvm_run *run = vcpu->run;
+ struct timespec start;
+ struct timespec ts_diff;
+ int ret;
+
+ clock_gettime(CLOCK_MONOTONIC, &start);
+
+ /* Let the guest access its memory */
+ ret = _vcpu_run(vcpu);
+ TEST_ASSERT(ret == 0, "vcpu_run failed: %d", ret);
+ if (get_ucall(vcpu, NULL) != UCALL_SYNC) {
+ TEST_ASSERT(false,
+ "Invalid guest sync status: exit_reason=%s",
+ exit_reason_str(run->exit_reason));
+ }
+
+ ts_diff = timespec_elapsed(start);
+ PER_VCPU_DEBUG("vCPU %d execution time: %ld.%.9lds\n", vcpu_idx,
+ ts_diff.tv_sec, ts_diff.tv_nsec);
+}
+
+static int handle_uffd_page_request(int uffd_mode, int uffd,
+ struct uffd_msg *msg)
+{
+ pid_t tid = syscall(__NR_gettid);
+ uint64_t addr = msg->arg.pagefault.address;
+ struct timespec start;
+ struct timespec ts_diff;
+ int r;
+
+ clock_gettime(CLOCK_MONOTONIC, &start);
+
+ if (uffd_mode == UFFDIO_REGISTER_MODE_MISSING) {
+ struct uffdio_copy copy;
+
+ copy.src = (uint64_t)guest_data_prototype;
+ copy.dst = addr;
+ copy.len = demand_paging_size;
+ copy.mode = 0;
+
+ r = ioctl(uffd, UFFDIO_COPY, &copy);
+ /*
+ * 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.
+ *
+ * Note that this also suppress any EEXISTs occurring from,
+ * e.g., the first UFFDIO_COPY/CONTINUEs on a page. That never
+ * happens here, but a realistic VMM might potentially maintain
+ * some external state to correctly surface EEXISTs to userspace
+ * (or prevent duplicate COPY/CONTINUEs in the first place).
+ */
+ if (r == -1 && errno != EEXIST) {
+ pr_info("Failed UFFDIO_COPY in 0x%lx from thread %d, errno = %d\n",
+ addr, tid, errno);
+ return r;
+ }
+ } else if (uffd_mode == UFFDIO_REGISTER_MODE_MINOR) {
+ struct uffdio_continue cont = {0};
+
+ cont.range.start = addr;
+ cont.range.len = demand_paging_size;
+
+ r = ioctl(uffd, UFFDIO_CONTINUE, &cont);
+ /*
+ * 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.
+ *
+ * Note that this also suppress any EEXISTs occurring from,
+ * e.g., the first UFFDIO_COPY/CONTINUEs on a page. That never
+ * happens here, but a realistic VMM might potentially maintain
+ * some external state to correctly surface EEXISTs to userspace
+ * (or prevent duplicate COPY/CONTINUEs in the first place).
+ */
+ if (r == -1 && errno != EEXIST) {
+ pr_info("Failed UFFDIO_CONTINUE in 0x%lx, thread %d, errno = %d\n",
+ addr, tid, errno);
+ return r;
+ }
+ } else {
+ TEST_FAIL("Invalid uffd mode %d", uffd_mode);
+ }
+
+ ts_diff = timespec_elapsed(start);
+
+ PER_PAGE_DEBUG("UFFD page-in %d \t%ld ns\n", tid,
+ timespec_to_ns(ts_diff));
+ PER_PAGE_DEBUG("Paged in %ld bytes at 0x%lx from thread %d\n",
+ demand_paging_size, addr, tid);
+
+ return 0;
+}
+
+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;
+};
+
+static void prefault_mem(void *alias, uint64_t len)
+{
+ size_t p;
+
+ TEST_ASSERT(alias != NULL, "Alias required for minor faults");
+ for (p = 0; p < (len / demand_paging_size); ++p) {
+ memcpy(alias + (p * demand_paging_size),
+ guest_data_prototype, demand_paging_size);
+ }
+}
+
+static void run_test(enum vm_guest_mode mode, void *arg)
+{
+ struct memstress_vcpu_args *vcpu_args;
+ struct test_params *p = arg;
+ struct uffd_desc **uffd_descs = NULL;
+ uint64_t uffd_region_size;
+ struct timespec start;
+ struct timespec ts_diff;
+ double vcpu_paging_rate;
+ struct kvm_vm *vm;
+ int i, num_uffds = 0;
+
+ vm = memstress_create_vm(mode, nr_vcpus, guest_percpu_mem_size, 1,
+ p->src_type, p->partition_vcpu_memory_access);
+
+ demand_paging_size = get_backing_src_pagesz(p->src_type);
+
+ guest_data_prototype = malloc(demand_paging_size);
+ TEST_ASSERT(guest_data_prototype,
+ "Failed to allocate buffer for guest data pattern");
+ memset(guest_data_prototype, 0xAB, demand_paging_size);
+
+ if (p->uffd_mode == UFFDIO_REGISTER_MODE_MINOR) {
+ num_uffds = p->single_uffd ? 1 : nr_vcpus;
+ for (i = 0; i < num_uffds; i++) {
+ vcpu_args = &memstress_args.vcpu_args[i];
+ prefault_mem(addr_gpa2alias(vm, vcpu_args->gpa),
+ vcpu_args->pages * memstress_args.guest_page_size);
+ }
+ }
+
+ if (p->uffd_mode) {
+ 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 < num_uffds; i++) {
+ struct memstress_vcpu_args *vcpu_args;
+ void *vcpu_hva;
+
+ vcpu_args = &memstress_args.vcpu_args[i];
+
+ /* Cache the host addresses of the region */
+ vcpu_hva = addr_gpa2hva(vm, vcpu_args->gpa);
+ /*
+ * Set up user fault fd to handle demand paging
+ * requests.
+ */
+ uffd_descs[i] = uffd_setup_demand_paging(
+ p->uffd_mode, p->uffd_delay, vcpu_hva,
+ uffd_region_size,
+ p->readers_per_uffd,
+ &handle_uffd_page_request);
+ }
+ }
+
+ pr_info("Finished creating vCPUs and starting uffd threads\n");
+
+ clock_gettime(CLOCK_MONOTONIC, &start);
+ memstress_start_vcpu_threads(nr_vcpus, vcpu_worker);
+ pr_info("Started all vCPUs\n");
+
+ memstress_join_vcpu_threads(nr_vcpus);
+ ts_diff = timespec_elapsed(start);
+ pr_info("All vCPU threads joined\n");
+
+ if (p->uffd_mode) {
+ /* Tell the user fault fd handler threads to quit */
+ for (i = 0; i < num_uffds; i++)
+ uffd_stop_demand_paging(uffd_descs[i]);
+ }
+
+ pr_info("Total guest execution time:\t%ld.%.9lds\n",
+ ts_diff.tv_sec, ts_diff.tv_nsec);
+
+ vcpu_paging_rate = memstress_args.vcpu_args[0].pages /
+ ((double)ts_diff.tv_sec + (double)ts_diff.tv_nsec / NSEC_PER_SEC);
+ pr_info("Per-vcpu demand paging rate:\t%f pgs/sec/vcpu\n",
+ vcpu_paging_rate);
+ pr_info("Overall demand paging rate:\t%f pgs/sec\n",
+ vcpu_paging_rate * nr_vcpus);
+
+ memstress_destroy_vm(vm);
+
+ free(guest_data_prototype);
+ if (p->uffd_mode)
+ free(uffd_descs);
+}
+
+static void help(char *name)
+{
+ puts("");
+ 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] [-c cpu_list] [-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");
+ kvm_print_vcpu_pinning_help();
+ 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");
+ backing_src_help("-s");
+ printf(" -v: specify the number of vCPUs to run.\n");
+ printf(" -o: Overlap guest memory accesses instead of partitioning\n"
+ " them into a separate region of memory for each vCPU.\n");
+ puts("");
+ exit(0);
+}
+
+int main(int argc, char *argv[])
+{
+ int max_vcpus = kvm_check_cap(KVM_CAP_MAX_VCPUS);
+ const char *cpulist = NULL;
+ 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, "ahom:u:d:b:s:v:c:r:")) != -1) {
+ switch (opt) {
+ case 'm':
+ guest_modes_cmdline(optarg);
+ break;
+ case 'u':
+ if (!strcmp("MISSING", optarg))
+ p.uffd_mode = UFFDIO_REGISTER_MODE_MISSING;
+ else if (!strcmp("MINOR", optarg))
+ 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.");
+ break;
+ case 'b':
+ guest_percpu_mem_size = parse_size(optarg);
+ break;
+ case 's':
+ p.src_type = parse_backing_src_type(optarg);
+ break;
+ case 'v':
+ nr_vcpus = atoi_positive("Number of vCPUs", optarg);
+ TEST_ASSERT(nr_vcpus <= max_vcpus,
+ "Invalid number of vcpus, must be between 1 and %d", max_vcpus);
+ break;
+ case 'c':
+ cpulist = optarg;
+ 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:
+ help(argv[0]);
+ break;
+ }
+ }
+
+ if (p.uffd_mode == UFFDIO_REGISTER_MODE_MINOR &&
+ !backing_src_is_shared(p.src_type)) {
+ TEST_FAIL("userfaultfd MINOR mode requires shared memory; pick a different -s");
+ }
+
+ if (cpulist) {
+ kvm_parse_vcpu_pinning(cpulist, memstress_args.vcpu_to_pcpu,
+ nr_vcpus);
+ memstress_args.pin_vcpus = true;
+ }
+
+ for_each_guest_mode(run_test, &p);
+
+ return 0;
+}
+
+#else /* __NR_userfaultfd */
+
+#warning "missing __NR_userfaultfd definition"
+
+int main(void)
+{
+ print_skip("__NR_userfaultfd must be present for userfaultfd test");
+ return KSFT_SKIP;
+}
+
+#endif /* __NR_userfaultfd */
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