[RFC PATCH 38/39] KVM: selftests: Update private_mem_conversions_test for mmap()able guest_memfd

From: Ackerley Tng
Date: Tue Sep 10 2024 - 19:58:10 EST

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Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
---
.../kvm/x86_64/private_mem_conversions_test.c | 146 +++++++++++++++---
.../x86_64/private_mem_conversions_test.sh | 3 +
2 files changed, 124 insertions(+), 25 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c b/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c
index 71f480c19f92..6524ef398584 100644
--- a/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c
@@ -11,6 +11,8 @@
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/wait.h>

#include <linux/compiler.h>
#include <linux/kernel.h>
@@ -202,15 +204,19 @@ static void guest_test_explicit_conversion(uint64_t base_gpa, bool do_fallocate)
guest_sync_shared(gpa, size, p3, p4);
memcmp_g(gpa, p4, size);

- /* Reset the shared memory back to the initial pattern. */
- memset((void *)gpa, init_p, size);
-
/*
* Free (via PUNCH_HOLE) *all* private memory so that the next
* iteration starts from a clean slate, e.g. with respect to
* whether or not there are pages/folios in guest_mem.
*/
guest_map_shared(base_gpa, PER_CPU_DATA_SIZE, true);
+
+ /*
+ * Reset the entire block back to the initial pattern. Do this
+ * after fallocate(PUNCH_HOLE) because hole-punching zeroes
+ * memory.
+ */
+ memset((void *)base_gpa, init_p, PER_CPU_DATA_SIZE);
}
}

@@ -286,7 +292,8 @@ static void guest_code(uint64_t base_gpa)
GUEST_DONE();
}

-static void handle_exit_hypercall(struct kvm_vcpu *vcpu)
+static void handle_exit_hypercall(struct kvm_vcpu *vcpu,
+ bool back_shared_memory_with_guest_memfd)
{
struct kvm_run *run = vcpu->run;
uint64_t gpa = run->hypercall.args[0];
@@ -303,17 +310,46 @@ static void handle_exit_hypercall(struct kvm_vcpu *vcpu)
if (do_fallocate)
vm_guest_mem_fallocate(vm, gpa, size, map_shared);

- if (set_attributes)
+ if (set_attributes) {
+ if (back_shared_memory_with_guest_memfd && !map_shared)
+ vm_guest_mem_madvise(vm, gpa, size, MADV_DONTNEED);
vm_set_memory_attributes(vm, gpa, size,
map_shared ? 0 : KVM_MEMORY_ATTRIBUTE_PRIVATE);
+ }
run->hypercall.ret = 0;
}

+static void assert_not_faultable(uint8_t *address)
+{
+ pid_t child_pid;
+
+ child_pid = fork();
+ TEST_ASSERT(child_pid != -1, "fork failed");
+
+ if (child_pid == 0) {
+ *address = 'A';
+ } else {
+ int status;
+ waitpid(child_pid, &status, 0);
+
+ TEST_ASSERT(WIFSIGNALED(status),
+ "Child should have exited with a signal");
+ TEST_ASSERT_EQ(WTERMSIG(status), SIGBUS);
+ }
+}
+
static bool run_vcpus;

-static void *__test_mem_conversions(void *__vcpu)
+struct test_thread_args
{
- struct kvm_vcpu *vcpu = __vcpu;
+ struct kvm_vcpu *vcpu;
+ bool back_shared_memory_with_guest_memfd;
+};
+
+static void *__test_mem_conversions(void *params)
+{
+ struct test_thread_args *args = params;
+ struct kvm_vcpu *vcpu = args->vcpu;
struct kvm_run *run = vcpu->run;
struct kvm_vm *vm = vcpu->vm;
struct ucall uc;
@@ -325,7 +361,8 @@ static void *__test_mem_conversions(void *__vcpu)
vcpu_run(vcpu);

if (run->exit_reason == KVM_EXIT_HYPERCALL) {
- handle_exit_hypercall(vcpu);
+ handle_exit_hypercall(vcpu,
+ args->back_shared_memory_with_guest_memfd);
continue;
}

@@ -349,8 +386,18 @@ static void *__test_mem_conversions(void *__vcpu)
size_t nr_bytes = min_t(size_t, vm->page_size, size - i);
uint8_t *hva = addr_gpa2hva(vm, gpa + i);

- /* In all cases, the host should observe the shared data. */
- memcmp_h(hva, gpa + i, uc.args[3], nr_bytes);
+ /* Check contents of memory */
+ if (args->back_shared_memory_with_guest_memfd &&
+ uc.args[0] == SYNC_PRIVATE) {
+ assert_not_faultable(hva);
+ } else {
+ /*
+ * If shared and private memory use
+ * separate backing memory, the host
+ * should always observe shared data.
+ */
+ memcmp_h(hva, gpa + i, uc.args[3], nr_bytes);
+ }

/* For shared, write the new pattern to guest memory. */
if (uc.args[0] == SYNC_SHARED)
@@ -366,11 +413,41 @@ static void *__test_mem_conversions(void *__vcpu)
}
}

-static void
-test_mem_conversions(enum vm_mem_backing_src_type src_type,
- enum vm_private_mem_backing_src_type private_mem_src_type,
- uint32_t nr_vcpus,
- uint32_t nr_memslots)
+static void add_memslot(struct kvm_vm *vm, uint64_t gpa, uint32_t slot,
+ uint64_t size, int guest_memfd,
+ uint64_t guest_memfd_offset,
+ enum vm_mem_backing_src_type src_type,
+ bool back_shared_memory_with_guest_memfd)
+{
+ struct userspace_mem_region *region;
+
+ if (!back_shared_memory_with_guest_memfd) {
+ vm_mem_add(vm, src_type, gpa, slot, size / vm->page_size,
+ KVM_MEM_GUEST_MEMFD, guest_memfd,
+ guest_memfd_offset);
+ return;
+ }
+
+ region = vm_mem_region_alloc(vm);
+
+ guest_memfd = vm_mem_region_install_guest_memfd(region, guest_memfd);
+
+ vm_mem_region_mmap(region, size, MAP_SHARED, guest_memfd, guest_memfd_offset);
+ vm_mem_region_install_memory(region, size, getpagesize());
+
+ region->region.slot = slot;
+ region->region.flags = KVM_MEM_GUEST_MEMFD;
+ region->region.guest_phys_addr = gpa;
+ region->region.guest_memfd_offset = guest_memfd_offset;
+
+ vm_mem_region_add(vm, region);
+}
+
+static void test_mem_conversions(enum vm_mem_backing_src_type src_type,
+ enum vm_private_mem_backing_src_type private_mem_src_type,
+ uint32_t nr_vcpus,
+ uint32_t nr_memslots,
+ bool back_shared_memory_with_guest_memfd)
{
/*
* Allocate enough memory so that each vCPU's chunk of memory can be
@@ -381,6 +458,7 @@ test_mem_conversions(enum vm_mem_backing_src_type src_type,
get_private_mem_backing_src_pagesz(private_mem_src_type),
get_backing_src_pagesz(src_type)));
const size_t per_cpu_size = align_up(PER_CPU_DATA_SIZE, alignment);
+ struct test_thread_args *thread_args[KVM_MAX_VCPUS];
const size_t memfd_size = per_cpu_size * nr_vcpus;
const size_t slot_size = memfd_size / nr_memslots;
struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
@@ -404,13 +482,14 @@ test_mem_conversions(enum vm_mem_backing_src_type src_type,
vm, memfd_size,
vm_private_mem_backing_src_alias(private_mem_src_type)->flag);

- for (i = 0; i < nr_memslots; i++)
- vm_mem_add(vm, src_type, BASE_DATA_GPA + slot_size * i,
- BASE_DATA_SLOT + i, slot_size / vm->page_size,
- KVM_MEM_GUEST_MEMFD, memfd, slot_size * i);
+ for (i = 0; i < nr_memslots; i++) {
+ add_memslot(vm, BASE_DATA_GPA + slot_size * i,
+ BASE_DATA_SLOT + i, slot_size, memfd, slot_size * i,
+ src_type, back_shared_memory_with_guest_memfd);
+ }

for (i = 0; i < nr_vcpus; i++) {
- uint64_t gpa = BASE_DATA_GPA + i * per_cpu_size;
+ uint64_t gpa = BASE_DATA_GPA + i * per_cpu_size;

vcpu_args_set(vcpus[i], 1, gpa);

@@ -420,13 +499,23 @@ test_mem_conversions(enum vm_mem_backing_src_type src_type,
*/
virt_map(vm, gpa, gpa, PER_CPU_DATA_SIZE / vm->page_size);

- pthread_create(&threads[i], NULL, __test_mem_conversions, vcpus[i]);
+ thread_args[i] = malloc(sizeof(struct test_thread_args));
+ TEST_ASSERT(thread_args[i] != NULL,
+ "Could not allocate memory for thread parameters");
+ thread_args[i]->vcpu = vcpus[i];
+ thread_args[i]->back_shared_memory_with_guest_memfd =
+ back_shared_memory_with_guest_memfd;
+
+ pthread_create(&threads[i], NULL, __test_mem_conversions,
+ (void *)thread_args[i]);
}

WRITE_ONCE(run_vcpus, true);

- for (i = 0; i < nr_vcpus; i++)
+ for (i = 0; i < nr_vcpus; i++) {
pthread_join(threads[i], NULL);
+ free(thread_args[i]);
+ }

kvm_vm_free(vm);

@@ -448,7 +537,7 @@ test_mem_conversions(enum vm_mem_backing_src_type src_type,
static void usage(const char *cmd)
{
puts("");
- printf("usage: %s [-h] [-m nr_memslots] [-s mem_type] [-p private_mem_type] [-n nr_vcpus]\n", cmd);
+ printf("usage: %s [-h] [-m nr_memslots] [-s mem_type] [-p private_mem_type] [-n nr_vcpus] [-g]\n", cmd);
puts("");
backing_src_help("-s");
puts("");
@@ -458,19 +547,22 @@ static void usage(const char *cmd)
puts("");
puts(" -m: specify the number of memslots (default: 1)");
puts("");
+ puts(" -g: back shared memory with guest_memfd (default: false)");
+ puts("");
}

int main(int argc, char *argv[])
{
enum vm_mem_backing_src_type src_type = DEFAULT_VM_MEM_SRC;
enum vm_private_mem_backing_src_type private_mem_src_type = DEFAULT_VM_PRIVATE_MEM_SRC;
+ bool back_shared_memory_with_guest_memfd = false;
uint32_t nr_memslots = 1;
uint32_t nr_vcpus = 1;
int opt;

TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM));

- while ((opt = getopt(argc, argv, "hm:s:p:n:")) != -1) {
+ while ((opt = getopt(argc, argv, "hgm:s:p:n:")) != -1) {
switch (opt) {
case 's':
src_type = parse_backing_src_type(optarg);
@@ -484,6 +576,9 @@ int main(int argc, char *argv[])
case 'm':
nr_memslots = atoi_positive("nr_memslots", optarg);
break;
+ case 'g':
+ back_shared_memory_with_guest_memfd = true;
+ break;
case 'h':
default:
usage(argv[0]);
@@ -491,7 +586,8 @@ int main(int argc, char *argv[])
}
}

- test_mem_conversions(src_type, private_mem_src_type, nr_vcpus, nr_memslots);
+ test_mem_conversions(src_type, private_mem_src_type, nr_vcpus, nr_memslots,
+ back_shared_memory_with_guest_memfd);

return 0;
}
diff --git a/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.sh b/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.sh
index fb6705fef466..c7f3dfee0336 100755
--- a/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.sh
+++ b/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.sh
@@ -75,6 +75,9 @@ TEST_EXECUTABLE="$(dirname "$0")/private_mem_conversions_test"
$TEST_EXECUTABLE -s "$src_type" -p "$private_mem_src_type" -n $num_vcpus_to_test
$TEST_EXECUTABLE -s "$src_type" -p "$private_mem_src_type" -n $num_vcpus_to_test -m $num_memslots_to_test

+ $TEST_EXECUTABLE -s "$src_type" -p "$private_mem_src_type" -n $num_vcpus_to_test -g
+ $TEST_EXECUTABLE -s "$src_type" -p "$private_mem_src_type" -n $num_vcpus_to_test -m $num_memslots_to_test -g
+
{ set +x; } 2>/dev/null

echo
--
2.46.0.598.g6f2099f65c-goog

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