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KVM: selftests: guest_memfd mmap() test when mmap is supported

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Expand the guest_memfd selftests to comprehensively test host userspace
mmap functionality for guest_memfd-backed memory when supported by the
VM type.

Introduce new test cases to verify the following:

* Successful mmap operations: Ensure that MAP_SHARED mappings succeed
  when guest_memfd mmap is enabled.

* Data integrity: Validate that data written to the mmap'd region is
  correctly persistent and readable.

* fallocate interaction: Test that fallocate(FALLOC_FL_PUNCH_HOLE)
  correctly zeros out mapped pages.

* Out-of-bounds access: Verify that accessing memory beyond the
  guest_memfd's size correctly triggers a SIGBUS signal.

* Unsupported mmap: Confirm that mmap attempts fail as expected when
  guest_memfd mmap support is not enabled for the specific guest_memfd
  instance or VM type.

* Flag validity: Introduce test_vm_type_gmem_flag_validity() to
  systematically test that only allowed guest_memfd creation flags are
  accepted for different VM types (e.g., GUEST_MEMFD_FLAG_MMAP for
  default VMs, no flags for CoCo VMs).

The existing tests for guest_memfd creation (multiple instances, invalid
sizes), file read/write, file size, and invalid punch hole operations
are integrated into the new test_with_type() framework to allow testing
across different VM types.

Cc: James Houghton <jthoughton@google.com>
Cc: Gavin Shan <gshan@redhat.com>
Cc: Shivank Garg <shivankg@amd.com>
Co-developed-by: Ackerley Tng <ackerleytng@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
Signed-off-by: Fuad Tabba <tabba@google.com>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20250729225455.670324-24-seanjc@google.com>
[Fix default vm_types to use BIT() - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Fuad Tabba 2025-07-29 15:54:54 -07:00 committed by Paolo Bonzini
parent 692f6ecf38
commit a11d7124b4
1 changed files with 139 additions and 22 deletions
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161
tools/testing/selftests/kvm/guest_memfd_test.c
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@ -13,6 +13,8 @@
#include <linux/bitmap.h>
#include <linux/falloc.h>
#include <setjmp.h>
#include <signal.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
@ -34,12 +36,83 @@ static void test_file_read_write(int fd)
"pwrite on a guest_mem fd should fail");
}
static void test_mmap(int fd, size_t page_size)
static void test_mmap_supported(int fd, size_t page_size, size_t total_size)
{
const char val = 0xaa;
char *mem;
size_t i;
int ret;
mem = mmap(NULL, total_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
TEST_ASSERT(mem == MAP_FAILED, "Copy-on-write not allowed by guest_memfd.");
mem = mmap(NULL, total_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
TEST_ASSERT(mem != MAP_FAILED, "mmap() for guest_memfd should succeed.");
memset(mem, val, total_size);
for (i = 0; i < total_size; i++)
TEST_ASSERT_EQ(READ_ONCE(mem[i]), val);
ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0,
page_size);
TEST_ASSERT(!ret, "fallocate the first page should succeed.");
for (i = 0; i < page_size; i++)
TEST_ASSERT_EQ(READ_ONCE(mem[i]), 0x00);
for (; i < total_size; i++)
TEST_ASSERT_EQ(READ_ONCE(mem[i]), val);
memset(mem, val, page_size);
for (i = 0; i < total_size; i++)
TEST_ASSERT_EQ(READ_ONCE(mem[i]), val);
ret = munmap(mem, total_size);
TEST_ASSERT(!ret, "munmap() should succeed.");
}
static sigjmp_buf jmpbuf;
void fault_sigbus_handler(int signum)
{
siglongjmp(jmpbuf, 1);
}
static void test_fault_overflow(int fd, size_t page_size, size_t total_size)
{
struct sigaction sa_old, sa_new = {
.sa_handler = fault_sigbus_handler,
};
size_t map_size = total_size * 4;
const char val = 0xaa;
char *mem;
size_t i;
int ret;
mem = mmap(NULL, map_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
TEST_ASSERT(mem != MAP_FAILED, "mmap() for guest_memfd should succeed.");
sigaction(SIGBUS, &sa_new, &sa_old);
if (sigsetjmp(jmpbuf, 1) == 0) {
memset(mem, 0xaa, map_size);
TEST_ASSERT(false, "memset() should have triggered SIGBUS.");
}
sigaction(SIGBUS, &sa_old, NULL);
for (i = 0; i < total_size; i++)
TEST_ASSERT_EQ(READ_ONCE(mem[i]), val);
ret = munmap(mem, map_size);
TEST_ASSERT(!ret, "munmap() should succeed.");
}
static void test_mmap_not_supported(int fd, size_t page_size, size_t total_size)
{
char *mem;
mem = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
TEST_ASSERT_EQ(mem, MAP_FAILED);
mem = mmap(NULL, total_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
TEST_ASSERT_EQ(mem, MAP_FAILED);
}
static void test_file_size(int fd, size_t page_size, size_t total_size)
@ -120,26 +193,19 @@ static void test_invalid_punch_hole(int fd, size_t page_size, size_t total_size)
}
}
static void test_create_guest_memfd_invalid(struct kvm_vm *vm)
static void test_create_guest_memfd_invalid_sizes(struct kvm_vm *vm,
uint64_t guest_memfd_flags,
size_t page_size)
{
size_t page_size = getpagesize();
uint64_t flag;
size_t size;
int fd;
for (size = 1; size < page_size; size++) {
fd = __vm_create_guest_memfd(vm, size, 0);
TEST_ASSERT(fd == -1 && errno == EINVAL,
fd = __vm_create_guest_memfd(vm, size, guest_memfd_flags);
TEST_ASSERT(fd < 0 && errno == EINVAL,
"guest_memfd() with non-page-aligned page size '0x%lx' should fail with EINVAL",
size);
}
for (flag = BIT(0); flag; flag <<= 1) {
fd = __vm_create_guest_memfd(vm, page_size, flag);
TEST_ASSERT(fd == -1 && errno == EINVAL,
"guest_memfd() with flag '0x%lx' should fail with EINVAL",
flag);
}
}
static void test_create_guest_memfd_multiple(struct kvm_vm *vm)
@ -171,30 +237,81 @@ static void test_create_guest_memfd_multiple(struct kvm_vm *vm)
close(fd1);
}
int main(int argc, char *argv[])
static void test_guest_memfd_flags(struct kvm_vm *vm, uint64_t valid_flags)
{
size_t page_size;
size_t total_size;
size_t page_size = getpagesize();
uint64_t flag;
int fd;
struct kvm_vm *vm;
TEST_REQUIRE(kvm_has_cap(KVM_CAP_GUEST_MEMFD));
for (flag = BIT(0); flag; flag <<= 1) {
fd = __vm_create_guest_memfd(vm, page_size, flag);
if (flag & valid_flags) {
TEST_ASSERT(fd >= 0,
"guest_memfd() with flag '0x%lx' should succeed",
flag);
close(fd);
} else {
TEST_ASSERT(fd < 0 && errno == EINVAL,
"guest_memfd() with flag '0x%lx' should fail with EINVAL",
flag);
}
}
}
static void test_guest_memfd(unsigned long vm_type)
{
uint64_t flags = 0;
struct kvm_vm *vm;
size_t total_size;
size_t page_size;
int fd;
page_size = getpagesize();
total_size = page_size * 4;
vm = vm_create_barebones();
vm = vm_create_barebones_type(vm_type);
if (vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_MMAP))
flags |= GUEST_MEMFD_FLAG_MMAP;
test_create_guest_memfd_invalid(vm);
test_create_guest_memfd_multiple(vm);
test_create_guest_memfd_invalid_sizes(vm, flags, page_size);
fd = vm_create_guest_memfd(vm, total_size, 0);
fd = vm_create_guest_memfd(vm, total_size, flags);
test_file_read_write(fd);
test_mmap(fd, page_size);
if (flags & GUEST_MEMFD_FLAG_MMAP) {
test_mmap_supported(fd, page_size, total_size);
test_fault_overflow(fd, page_size, total_size);
} else {
test_mmap_not_supported(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);
test_guest_memfd_flags(vm, flags);
close(fd);
kvm_vm_free(vm);
}
int main(int argc, char *argv[])
{
unsigned long vm_types, vm_type;
TEST_REQUIRE(kvm_has_cap(KVM_CAP_GUEST_MEMFD));
/*
* Not all architectures support KVM_CAP_VM_TYPES. However, those that
* support guest_memfd have that support for the default VM type.
*/
vm_types = kvm_check_cap(KVM_CAP_VM_TYPES);
if (!vm_types)
vm_types = BIT(VM_TYPE_DEFAULT);
for_each_set_bit(vm_type, &vm_types, BITS_PER_TYPE(vm_types))
test_guest_memfd(vm_type);
}