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KVM: selftests: Verify that faulting in private guest_memfd memory fails

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Add a guest_memfd testcase to verify that faulting in private memory gets
a SIGBUS.  For now, test only the case where memory is private by default
since KVM doesn't yet support in-place conversion.

Deliberately run the CoW test with and without INIT_SHARED set as KVM
should disallow MAP_PRIVATE regardless of whether the memory itself is
private from a CoCo perspective.

Cc: Ackerley Tng <ackerleytng@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Ackerley Tng <ackerleytng@google.com>
Tested-by: Ackerley Tng <ackerleytng@google.com>
Link: https://lore.kernel.org/r/20251003232606.4070510-13-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2025-10-03 16:26:05 -07:00
parent f91187c0ec
commit 19942d4fd9
1 changed files with 21 additions and 5 deletions
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26
tools/testing/selftests/kvm/guest_memfd_test.c
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@ -75,9 +75,8 @@ static void test_mmap_supported(int fd, size_t total_size)
kvm_munmap(mem, total_size);
}
static void test_fault_overflow(int fd, size_t total_size)
static void test_fault_sigbus(int fd, size_t accessible_size, size_t map_size)
{
size_t map_size = total_size * 4;
const char val = 0xaa;
char *mem;
size_t i;
@ -86,12 +85,22 @@ static void test_fault_overflow(int fd, size_t total_size)
TEST_EXPECT_SIGBUS(memset(mem, val, map_size));
for (i = 0; i < total_size; i++)
for (i = 0; i < accessible_size; i++)
TEST_ASSERT_EQ(READ_ONCE(mem[i]), val);
kvm_munmap(mem, map_size);
}
static void test_fault_overflow(int fd, size_t total_size)
{
test_fault_sigbus(fd, total_size, total_size * 4);
}
static void test_fault_private(int fd, size_t total_size)
{
test_fault_sigbus(fd, 0, total_size);
}
static void test_mmap_not_supported(int fd, size_t total_size)
{
char *mem;
@ -260,9 +269,14 @@ static void __test_guest_memfd(struct kvm_vm *vm, uint64_t flags)
gmem_test(file_read_write, vm, flags);
if (flags & GUEST_MEMFD_FLAG_MMAP) {
gmem_test(mmap_supported, vm, flags);
if (flags & GUEST_MEMFD_FLAG_INIT_SHARED) {
gmem_test(mmap_supported, vm, flags);
gmem_test(fault_overflow, vm, flags);
} else {
gmem_test(fault_private, vm, flags);
}
gmem_test(mmap_cow, vm, flags);
gmem_test(fault_overflow, vm, flags);
} else {
gmem_test(mmap_not_supported, vm, flags);
}
@ -282,6 +296,8 @@ static void test_guest_memfd(unsigned long vm_type)
__test_guest_memfd(vm, 0);
flags = vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_FLAGS);
if (flags & GUEST_MEMFD_FLAG_MMAP)
__test_guest_memfd(vm, GUEST_MEMFD_FLAG_MMAP);
/* MMAP should always be supported if INIT_SHARED is supported. */
if (flags & GUEST_MEMFD_FLAG_INIT_SHARED)