// 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, ©);
/*
* 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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