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Message-ID: <3d2f49b409f1d6564eaff49494789908eb9b74e5.1747264138.git.ackerleytng@google.com>
Date: Wed, 14 May 2025 16:41:48 -0700
From: Ackerley Tng <ackerleytng@...gle.com>
To: kvm@...r.kernel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
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Subject: [RFC PATCH v2 09/51] KVM: selftests: Test faulting with respect to GUEST_MEMFD_FLAG_INIT_PRIVATE
Test that faulting is denied when guest_memfd's shareability is
initialized as private with GUEST_MEMFD_FLAG_INIT_PRIVATE and allowed
if the flag is not specified.
Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
Co-developed-by: Fuad Tabba <tabba@...gle.com>
Signed-off-by: Fuad Tabba <tabba@...gle.com>
Change-Id: Id93d4683b36fc5a9c924458d26f0525baed26435
---
.../testing/selftests/kvm/guest_memfd_test.c | 112 +++++++++++++++---
1 file changed, 97 insertions(+), 15 deletions(-)
diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
index 51d88acdf072..1e79382fd830 100644
--- a/tools/testing/selftests/kvm/guest_memfd_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_test.c
@@ -16,6 +16,7 @@
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
+#include <sys/wait.h>
#include "kvm_util.h"
#include "test_util.h"
@@ -34,7 +35,7 @@ static void test_file_read_write(int fd)
"pwrite on a guest_mem fd should fail");
}
-static void test_mmap_allowed(int fd, size_t page_size, size_t total_size)
+static void test_faulting_allowed(int fd, size_t page_size, size_t total_size)
{
const char val = 0xaa;
char *mem;
@@ -65,6 +66,53 @@ static void test_mmap_allowed(int fd, size_t page_size, size_t total_size)
TEST_ASSERT(!ret, "munmap should succeed");
}
+static void assert_not_faultable(char *address)
+{
+ pid_t child_pid;
+
+ child_pid = fork();
+ TEST_ASSERT(child_pid != -1, "fork failed");
+
+ if (child_pid == 0) {
+ *address = 'A';
+ TEST_FAIL("Child should have exited with a signal");
+ } 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 void test_faulting_sigbus(int fd, size_t total_size)
+{
+ char *mem;
+ int ret;
+
+ mem = mmap(NULL, total_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+ TEST_ASSERT(mem != MAP_FAILED, "mmaping() guest memory should pass.");
+
+ assert_not_faultable(mem);
+
+ ret = munmap(mem, total_size);
+ TEST_ASSERT(!ret, "munmap should succeed");
+}
+
+static void test_mmap_allowed(int fd, size_t total_size)
+{
+ char *mem;
+ int ret;
+
+ mem = mmap(NULL, total_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+ TEST_ASSERT(mem != MAP_FAILED, "mmaping() guest memory should pass.");
+
+ ret = munmap(mem, total_size);
+ TEST_ASSERT(!ret, "munmap should succeed");
+}
+
static void test_mmap_denied(int fd, size_t page_size, size_t total_size)
{
char *mem;
@@ -364,40 +412,74 @@ static void test_bind_guest_memfd_wrt_userspace_addr(struct kvm_vm *vm)
close(fd);
}
-static void test_with_type(unsigned long vm_type, uint64_t guest_memfd_flags,
- bool expect_mmap_allowed)
+static void test_guest_memfd_features(struct kvm_vm *vm, size_t page_size,
+ uint64_t guest_memfd_flags,
+ bool expect_mmap_allowed,
+ bool expect_faulting_allowed)
{
- struct kvm_vm *vm;
size_t total_size;
- size_t page_size;
int fd;
- if (!(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(vm_type)))
- return;
-
- page_size = getpagesize();
total_size = page_size * 4;
- vm = vm_create_barebones_type(vm_type);
+ if (expect_faulting_allowed)
+ TEST_REQUIRE(expect_mmap_allowed);
- test_create_guest_memfd_multiple(vm);
- test_bind_guest_memfd_wrt_userspace_addr(vm);
test_create_guest_memfd_invalid_sizes(vm, guest_memfd_flags, page_size);
fd = vm_create_guest_memfd(vm, total_size, guest_memfd_flags);
test_file_read_write(fd);
- if (expect_mmap_allowed)
- test_mmap_allowed(fd, page_size, total_size);
- else
+ if (expect_mmap_allowed) {
+ test_mmap_allowed(fd, total_size);
+
+ if (expect_faulting_allowed)
+ test_faulting_allowed(fd, page_size, total_size);
+ else
+ test_faulting_sigbus(fd, total_size);
+ } else {
test_mmap_denied(fd, page_size, total_size);
+ }
test_file_size(fd, page_size, total_size);
test_fallocate(fd, page_size, total_size);
test_invalid_punch_hole(fd, page_size, total_size);
close(fd);
+}
+
+static void test_with_type(unsigned long vm_type, uint64_t guest_memfd_flags,
+ bool expect_mmap_allowed)
+{
+ struct kvm_vm *vm;
+ size_t page_size;
+
+ if (!(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(vm_type)))
+ return;
+
+ vm = vm_create_barebones_type(vm_type);
+
+ test_create_guest_memfd_multiple(vm);
+ test_bind_guest_memfd_wrt_userspace_addr(vm);
+
+ page_size = getpagesize();
+ if (guest_memfd_flags & GUEST_MEMFD_FLAG_SUPPORT_SHARED) {
+ test_guest_memfd_features(vm, page_size, guest_memfd_flags,
+ expect_mmap_allowed, true);
+
+ if (kvm_has_cap(KVM_CAP_GMEM_CONVERSION)) {
+ uint64_t flags = guest_memfd_flags |
+ GUEST_MEMFD_FLAG_INIT_PRIVATE;
+
+ test_guest_memfd_features(vm, page_size, flags,
+ expect_mmap_allowed, false);
+ }
+ } else {
+ test_guest_memfd_features(vm, page_size, guest_memfd_flags,
+ expect_mmap_allowed, false);
+ }
+
kvm_vm_release(vm);
}
--
2.49.0.1045.g170613ef41-goog
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