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KVM: selftests: Add demand paging content to the demand paging test 

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>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Ben Gardon 2020-02-20 18:09:12 +01:00 committed by Paolo Bonzini
parent 025eed7b35
commit 4f72180eb4
2 changed files with 209 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
tools/arch/x86/include/asm/unistd_64.h
View File

@ -1,4 +1,7 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __NR_userfaultfd
#define __NR_userfaultfd 282
#endif
#ifndef __NR_perf_event_open
# define __NR_perf_event_open 298
#endif

210
tools/testing/selftests/kvm/demand_paging_test.c
View File

@ -11,16 +11,21 @@
#include <stdio.h>
#include <stdlib.h>
#include <sys/syscall.h>
#include <unistd.h>
#include <asm/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"
#include "processor.h"
#ifdef __NR_userfaultfd
#define VCPU_ID 1
/* The memory slot index demand page */
@ -39,6 +44,8 @@ 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 +117,169 @@ 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, &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 +336,16 @@ 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 +364,20 @@ 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 guest_mode {
@ -210,7 +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"
@ -219,6 +404,7 @@ static void help(char *name)
printf(" %d: %s%s\n", i, vm_guest_mode_string(i),
guest_modes[i].supported ? " (supported)" : "");
}
printf(" -u: Use User Fault FD to handle vCPU page faults.\n");
puts("");
exit(0);
}
@ -228,6 +414,7 @@ int main(int argc, char *argv[])
bool mode_selected = false;
unsigned int mode;
int opt, i;
bool use_uffd = false;
#ifdef __x86_64__
guest_mode_init(VM_MODE_PXXV48_4K, true, true);
@ -250,7 +437,7 @@ int main(int argc, char *argv[])
guest_mode_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) {
@ -263,6 +450,9 @@ int main(int argc, char *argv[])
"Guest mode ID %d too big", mode);
guest_modes[mode].enabled = true;
break;
case 'u':
use_uffd = true;
break;
case 'h':
default:
help(argv[0]);
@ -276,8 +466,20 @@ int main(int argc, char *argv[])
TEST_ASSERT(guest_modes[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;
}
#else /* __NR_userfaultfd */
#warning "missing __NR_userfaultfd definition"
int main(void)
{
printf("skip: Skipping userfaultfd test (missing __NR_userfaultfd)\n");
return KSFT_SKIP;
}
#endif /* __NR_userfaultfd */