[PATCH v7 10/13] KVM: selftests: aarch64: Add userfaultfd tests into page_fault_test

Ricardo Koller
2022-09-20T04:26:27Z

Add some userfaultfd tests into page_fault_test. Punch holes into the
data and/or page-table memslots, perform some accesses, and check that
the faults are taken (or not taken) when expected.

Signed-off-by: Ricardo Koller <ricarkol@google.com>
---
.../selftests/kvm/aarch64/page_fault_test.c | 190 +++++++++++++++++-
1 file changed, 188 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/kvm/aarch64/page_fault_test.c b/tools/testing/selftests/kvm/aarch64/page_fault_test.c
index 98f12e7af14b..f0cdd4e99dd0 100644
--- a/tools/testing/selftests/kvm/aarch64/page_fault_test.c
+++ b/tools/testing/selftests/kvm/aarch64/page_fault_test.c
@@ -35,6 +35,12 @@ static uint64_t *guest_test_memory = (uint64_t *)TEST_GVA;
#define PREPARE_FN_NR 10
#define CHECK_FN_NR 10

+static struct event_cnt {
+ int uffd_faults;
+ /* uffd_faults is incremented from multiple threads. */
+ pthread_mutex_t uffd_faults_mutex;
+} events;
+
struct test_desc {
const char *name;
uint64_t mem_mark_cmd;
@@ -42,11 +48,14 @@ struct test_desc {
bool (*guest_prepare[PREPARE_FN_NR])(void);
void (*guest_test)(void);
void (*guest_test_check[CHECK_FN_NR])(void);
+ uffd_handler_t uffd_pt_handler;
+ uffd_handler_t uffd_data_handler;
void (*dabt_handler)(struct ex_regs *regs);
void (*iabt_handler)(struct ex_regs *regs);
uint32_t pt_memslot_flags;
uint32_t data_memslot_flags;
bool skip;
+ struct event_cnt expected_events;
};

struct test_params {
@@ -263,7 +272,110 @@ static void no_iabt_handler(struct ex_regs *regs)
GUEST_ASSERT_1(false, regs->pc);
}

+static struct uffd_args {
+ char *copy;
+ void *hva;
+ uint64_t paging_size;
+} pt_args, data_args;
+
/* Returns true to continue the test, and false if it should be skipped. */
+static int uffd_generic_handler(int uffd_mode, int uffd,
+ struct uffd_msg *msg, struct uffd_args *args,
+ bool expect_write)
+{
+ uint64_t addr = msg->arg.pagefault.address;
+ uint64_t flags = msg->arg.pagefault.flags;
+ struct uffdio_copy copy;
+ int ret;
+
+ TEST_ASSERT(uffd_mode == UFFDIO_REGISTER_MODE_MISSING,
+ "The only expected UFFD mode is MISSING");
+ ASSERT_EQ(!!(flags & UFFD_PAGEFAULT_FLAG_WRITE), expect_write);
+ ASSERT_EQ(addr, (uint64_t)args->hva);
+
+ pr_debug("uffd fault: addr=%p write=%d\n",
+ (void *)addr, !!(flags & UFFD_PAGEFAULT_FLAG_WRITE));
+
+ copy.src = (uint64_t)args->copy;
+ copy.dst = addr;
+ copy.len = args->paging_size;
+ copy.mode = 0;
+
+ ret = ioctl(uffd, UFFDIO_COPY, &copy);
+ if (ret == -1) {
+ pr_info("Failed UFFDIO_COPY in 0x%lx with errno: %d\n",
+ addr, errno);
+ return ret;
+ }
+
+ pthread_mutex_lock(&events.uffd_faults_mutex);
+ events.uffd_faults += 1;
+ pthread_mutex_unlock(&events.uffd_faults_mutex);
+ return 0;
+}
+
+static int uffd_pt_write_handler(int mode, int uffd, struct uffd_msg *msg)
+{
+ return uffd_generic_handler(mode, uffd, msg, &pt_args, true);
+}
+
+static int uffd_data_write_handler(int mode, int uffd, struct uffd_msg *msg)
+{
+ return uffd_generic_handler(mode, uffd, msg, &data_args, true);
+}
+
+static int uffd_data_read_handler(int mode, int uffd, struct uffd_msg *msg)
+{
+ return uffd_generic_handler(mode, uffd, msg, &data_args, false);
+}
+
+static void setup_uffd_args(struct userspace_mem_region *region,
+ struct uffd_args *args)
+{
+ args->hva = (void *)region->region.userspace_addr;
+ args->paging_size = region->region.memory_size;
+
+ args->copy = malloc(args->paging_size);
+ TEST_ASSERT(args->copy, "Failed to allocate data copy.");
+ memcpy(args->copy, args->hva, args->paging_size);
+}
+
+static void setup_uffd(struct kvm_vm *vm, struct test_params *p,
+ struct uffd_desc **pt_uffd, struct uffd_desc **data_uffd)
+{
+ struct test_desc *test = p->test_desc;
+
+ setup_uffd_args(vm_get_mem_region(vm, MEM_REGION_PT), &pt_args);
+ setup_uffd_args(vm_get_mem_region(vm, MEM_REGION_DATA), &data_args);
+
+ *pt_uffd = NULL;
+ if (test->uffd_pt_handler)
+ *pt_uffd = uffd_setup_demand_paging(
+ UFFDIO_REGISTER_MODE_MISSING, 0,
+ pt_args.hva, pt_args.paging_size,
+ test->uffd_pt_handler);
+
+ *data_uffd = NULL;
+ if (test->uffd_data_handler)
+ *data_uffd = uffd_setup_demand_paging(
+ UFFDIO_REGISTER_MODE_MISSING, 0,
+ data_args.hva, data_args.paging_size,
+ test->uffd_data_handler);
+}
+
+static void free_uffd(struct test_desc *test, struct uffd_desc *pt_uffd,
+ struct uffd_desc *data_uffd)
+{
+ if (test->uffd_pt_handler)
+ uffd_stop_demand_paging(pt_uffd);
+ if (test->uffd_data_handler)
+ uffd_stop_demand_paging(data_uffd);
+
+ free(pt_args.copy);
+ free(data_args.copy);
+}
+
+/* Returns false if the test should be skipped. */
static bool punch_hole_in_memslot(struct kvm_vm *vm,
struct userspace_mem_region *region)
{
@@ -411,6 +523,11 @@ static void setup_memslots(struct kvm_vm *vm, struct test_params *p)
vm->memslots[MEM_REGION_DATA] = DATA_MEMSLOT;
}

+static void check_event_counts(struct test_desc *test)
+{
+ ASSERT_EQ(test->expected_events.uffd_faults, events.uffd_faults);
+}
+
static void print_test_banner(enum vm_guest_mode mode, struct test_params *p)
{
struct test_desc *test = p->test_desc;
@@ -421,12 +538,17 @@ static void print_test_banner(enum vm_guest_mode mode, struct test_params *p)
vm_mem_backing_src_alias(p->src_type)->name);
}

+static void reset_event_counts(void)
+{
+ memset(&events, 0, sizeof(events));
+}
+
/*
* This function either succeeds, skips the test (after setting test->skip), or
* fails with a TEST_FAIL that aborts all tests.
*/
static void vcpu_run_loop(struct kvm_vm *vm, struct kvm_vcpu *vcpu,
- struct test_desc *test)
+ struct test_desc *test)
{
struct ucall uc;

@@ -461,6 +583,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
struct test_desc *test = p->test_desc;
struct kvm_vm *vm;
struct kvm_vcpu *vcpu;
+ struct uffd_desc *pt_uffd, *data_uffd;

print_test_banner(mode, p);

@@ -473,7 +596,16 @@ static void run_test(enum vm_guest_mode mode, void *arg)

ucall_init(vm, NULL);

+ reset_event_counts();
+
+ /*
+ * Set some code in the data memslot for the guest to execute (only
+ * applicable to the EXEC tests). This has to be done before
+ * setup_uffd() as that function copies the memslot data for the uffd
+ * handler.
+ */
load_exec_code_for_test(vm);
+ setup_uffd(vm, p, &pt_uffd, &data_uffd);
setup_abort_handlers(vm, vcpu, test);
vcpu_args_set(vcpu, 1, test);

@@ -481,6 +613,14 @@ static void run_test(enum vm_guest_mode mode, void *arg)

ucall_uninit(vm);
kvm_vm_free(vm);
+ free_uffd(test, pt_uffd, data_uffd);
+
+ /*
+ * Make sure we check the events after the uffd threads have exited,
+ * which means they updated their respective event counters.
+ */
+ if (!test->skip)
+ check_event_counts(test);
}

static void help(char *name)
@@ -496,6 +636,7 @@ static void help(char *name)
#define SNAME(s) #s
#define SCAT2(a, b) SNAME(a ## _ ## b)
#define SCAT3(a, b, c) SCAT2(a, SCAT2(b, c))
+#define SCAT4(a, b, c, d) SCAT2(a, SCAT3(b, c, d))

#define _CHECK(_test) _CHECK_##_test
#define _PREPARE(_test) _PREPARE_##_test
@@ -514,7 +655,7 @@ static void help(char *name)
#define _CHECK_with_af guest_check_pte_af
#define _CHECK_no_af NULL

-/* Performs an access and checks that no faults were triggered. */
+/* Performs an access and checks that no faults (no events) were triggered. */
#define TEST_ACCESS(_access, _with_af, _mark_cmd) \
{ \
.name = SCAT3(_access, _with_af, #_mark_cmd), \
@@ -523,6 +664,21 @@ static void help(char *name)
.mem_mark_cmd = _mark_cmd, \
.guest_test = _access, \
.guest_test_check = { _CHECK(_with_af) }, \
+ .expected_events = { 0 }, \
+}
+
+#define TEST_UFFD(_access, _with_af, _mark_cmd, \
+ _uffd_data_handler, _uffd_pt_handler, _uffd_faults) \
+{ \
+ .name = SCAT4(uffd, _access, _with_af, #_mark_cmd), \
+ .guest_prepare = { _PREPARE(_with_af), \
+ _PREPARE(_access) }, \
+ .guest_test = _access, \
+ .mem_mark_cmd = _mark_cmd, \
+ .guest_test_check = { _CHECK(_with_af) }, \
+ .uffd_data_handler = _uffd_data_handler, \
+ .uffd_pt_handler = _uffd_pt_handler, \
+ .expected_events = { .uffd_faults = _uffd_faults, }, \
}

static struct test_desc tests[] = {
@@ -548,6 +704,36 @@ static struct test_desc tests[] = {
TEST_ACCESS(guest_at, no_af, CMD_HOLE_DATA),
TEST_ACCESS(guest_dc_zva, no_af, CMD_HOLE_DATA),

+ /*
+ * Punch holes in the test and PT memslots and mark them for
+ * userfaultfd handling. This should result in 2 faults: the test
+ * access and its respective S1 page table walk (S1PTW).
+ */
+ TEST_UFFD(guest_read64, with_af, CMD_HOLE_DATA | CMD_HOLE_PT,
+ uffd_data_read_handler, uffd_pt_write_handler, 2),
+ /* no_af should also lead to a PT write. */
+ TEST_UFFD(guest_read64, no_af, CMD_HOLE_DATA | CMD_HOLE_PT,
+ uffd_data_read_handler, uffd_pt_write_handler, 2),
+ /* Note how that cas invokes the read handler. */
+ TEST_UFFD(guest_cas, with_af, CMD_HOLE_DATA | CMD_HOLE_PT,
+ uffd_data_read_handler, uffd_pt_write_handler, 2),
+ /*
+ * Can't test guest_at with_af as it's IMPDEF whether the AF is set.
+ * The S1PTW fault should still be marked as a write.
+ */
+ TEST_UFFD(guest_at, no_af, CMD_HOLE_DATA | CMD_HOLE_PT,
+ uffd_data_read_handler, uffd_pt_write_handler, 1),
+ TEST_UFFD(guest_ld_preidx, with_af, CMD_HOLE_DATA | CMD_HOLE_PT,
+ uffd_data_read_handler, uffd_pt_write_handler, 2),
+ TEST_UFFD(guest_write64, with_af, CMD_HOLE_DATA | CMD_HOLE_PT,
+ uffd_data_write_handler, uffd_pt_write_handler, 2),
+ TEST_UFFD(guest_dc_zva, with_af, CMD_HOLE_DATA | CMD_HOLE_PT,
+ uffd_data_write_handler, uffd_pt_write_handler, 2),
+ TEST_UFFD(guest_st_preidx, with_af, CMD_HOLE_DATA | CMD_HOLE_PT,
+ uffd_data_write_handler, uffd_pt_write_handler, 2),
+ TEST_UFFD(guest_exec, with_af, CMD_HOLE_DATA | CMD_HOLE_PT,
+ uffd_data_read_handler, uffd_pt_write_handler, 2),
+
{ 0 }
};

--
2.37.3.968.ga6b4b080e4-goog