Test using guest_memfd from userspace, since guest_memfd now has mmap() support.
Tests:
1. mmap() should now always return a valid address 2. Test that madvise() doesn't give any issues when pages are not faulted in. 3. Test that pages should not be faultable before association with a memslot, and that faults result in SIGBUS. 4. Test that pages can be faulted if marked faultable, and the flow of setting a memory range as private, which is: a. madvise(MADV_DONTNEED) to request kernel to unmap pages b. Set memory attributes of VM to private Also test that if pages are still mapped, setting memory attributes will fail. 5. Test that madvise(MADV_REMOVE) can be used to remove pages from guest_memfd, forcing zeroing of those pages before the next time the pages are faulted in.
Signed-off-by: Ackerley Tng ackerleytng@google.com
--- .../testing/selftests/kvm/guest_memfd_test.c | 195 +++++++++++++++++- 1 file changed, 189 insertions(+), 6 deletions(-)
diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c index 3618ce06663e..b6f3c3e6d0dd 100644 --- a/tools/testing/selftests/kvm/guest_memfd_test.c +++ b/tools/testing/selftests/kvm/guest_memfd_test.c @@ -6,6 +6,7 @@ */ #include <stdlib.h> #include <string.h> +#include <sys/wait.h> #include <unistd.h> #include <errno.h> #include <stdio.h> @@ -35,12 +36,192 @@ 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_should_map_pages_into_userspace(int fd, size_t page_size) { char *mem;
mem = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); - TEST_ASSERT_EQ(mem, MAP_FAILED); + TEST_ASSERT(mem != MAP_FAILED, "mmap should return valid address"); + + TEST_ASSERT_EQ(munmap(mem, page_size), 0); +} + +static void test_madvise_no_error_when_pages_not_faulted(int fd, size_t page_size) +{ + char *mem; + + mem = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); + TEST_ASSERT(mem != MAP_FAILED, "mmap should return valid address"); + + TEST_ASSERT_EQ(madvise(mem, page_size, MADV_DONTNEED), 0); + + TEST_ASSERT_EQ(munmap(mem, page_size), 0); +} + +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'; + } 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); + } +} + +/* + * Pages should not be faultable before association with memslot because pages + * (in a KVM_X86_SW_PROTECTED_VM) only default to faultable at memslot + * association time. + */ +static void test_pages_not_faultable_if_not_associated_with_memslot(int fd, + size_t page_size) +{ + char *mem = mmap(NULL, page_size, PROT_READ | PROT_WRITE, + MAP_SHARED, fd, 0); + TEST_ASSERT(mem != MAP_FAILED, "mmap should return valid address"); + + assert_not_faultable(mem); + + TEST_ASSERT_EQ(munmap(mem, page_size), 0); +} + +static void test_pages_faultable_if_marked_faultable(struct kvm_vm *vm, int fd, + size_t page_size) +{ + char *mem; + uint64_t gpa = 0; + uint64_t guest_memfd_offset = 0; + + /* + * This test uses KVM_X86_SW_PROTECTED_VM is required to set + * arch.has_private_mem, to add a memslot with guest_memfd to a VM. + */ + if (!(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM))) { + printf("Faultability test skipped since KVM_X86_SW_PROTECTED_VM is not supported."); + return; + } + + mem = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, + guest_memfd_offset); + TEST_ASSERT(mem != MAP_FAILED, "mmap should return valid address"); + + /* + * Setting up this memslot with a KVM_X86_SW_PROTECTED_VM marks all + * offsets in the file as shared, allowing pages to be faulted in. + */ + vm_set_user_memory_region2(vm, 0, KVM_MEM_GUEST_MEMFD, gpa, page_size, + mem, fd, guest_memfd_offset); + + *mem = 'A'; + TEST_ASSERT_EQ(*mem, 'A'); + + /* Should fail since the page is still faulted in. */ + TEST_ASSERT_EQ(__vm_set_memory_attributes(vm, gpa, page_size, + KVM_MEMORY_ATTRIBUTE_PRIVATE), + -1); + TEST_ASSERT_EQ(errno, EINVAL); + + /* + * Use madvise() to remove the pages from userspace page tables, then + * test that the page is still faultable, and that page contents remain + * the same. + */ + madvise(mem, page_size, MADV_DONTNEED); + TEST_ASSERT_EQ(*mem, 'A'); + + /* Tell kernel to unmap the page from userspace. */ + madvise(mem, page_size, MADV_DONTNEED); + + /* Now kernel can set this page to private. */ + vm_mem_set_private(vm, gpa, page_size); + assert_not_faultable(mem); + + /* + * Should be able to fault again after setting this back to shared, and + * memory contents should be cleared since pages must be re-prepared for + * SHARED use. + */ + vm_mem_set_shared(vm, gpa, page_size); + TEST_ASSERT_EQ(*mem, 0); + + /* Cleanup */ + vm_set_user_memory_region2(vm, 0, KVM_MEM_GUEST_MEMFD, gpa, 0, mem, fd, + guest_memfd_offset); + + TEST_ASSERT_EQ(munmap(mem, page_size), 0); +} + +static void test_madvise_remove_releases_pages(struct kvm_vm *vm, int fd, + size_t page_size) +{ + char *mem; + uint64_t gpa = 0; + uint64_t guest_memfd_offset = 0; + + /* + * This test uses KVM_X86_SW_PROTECTED_VM is required to set + * arch.has_private_mem, to add a memslot with guest_memfd to a VM. + */ + if (!(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM))) { + printf("madvise test skipped since KVM_X86_SW_PROTECTED_VM is not supported."); + return; + } + + mem = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); + TEST_ASSERT(mem != MAP_FAILED, "mmap should return valid address"); + + /* + * Setting up this memslot with a KVM_X86_SW_PROTECTED_VM marks all + * offsets in the file as shared, allowing pages to be faulted in. + */ + vm_set_user_memory_region2(vm, 0, KVM_MEM_GUEST_MEMFD, gpa, page_size, + mem, fd, guest_memfd_offset); + + *mem = 'A'; + TEST_ASSERT_EQ(*mem, 'A'); + + /* + * MADV_DONTNEED causes pages to be removed from userspace page tables + * but should not release pages, hence page contents are kept. + */ + TEST_ASSERT_EQ(madvise(mem, page_size, MADV_DONTNEED), 0); + TEST_ASSERT_EQ(*mem, 'A'); + + /* + * MADV_REMOVE causes pages to be released. Pages are then zeroed when + * prepared for shared use, hence 0 is expected on next fault. + */ + TEST_ASSERT_EQ(madvise(mem, page_size, MADV_REMOVE), 0); + TEST_ASSERT_EQ(*mem, 0); + + TEST_ASSERT_EQ(munmap(mem, page_size), 0); + + /* Cleanup */ + vm_set_user_memory_region2(vm, 0, KVM_MEM_GUEST_MEMFD, gpa, 0, mem, fd, + guest_memfd_offset); +} + +static void test_using_memory_directly_from_userspace(struct kvm_vm *vm, + int fd, size_t page_size) +{ + test_mmap_should_map_pages_into_userspace(fd, page_size); + + test_madvise_no_error_when_pages_not_faulted(fd, page_size); + + test_pages_not_faultable_if_not_associated_with_memslot(fd, page_size); + + test_pages_faultable_if_marked_faultable(vm, fd, page_size); + + test_madvise_remove_releases_pages(vm, fd, page_size); }
static void test_file_size(int fd, size_t page_size, size_t total_size) @@ -180,18 +361,17 @@ static void test_guest_memfd(struct kvm_vm *vm, uint32_t flags, size_t page_size size_t total_size; int fd;
- TEST_REQUIRE(kvm_has_cap(KVM_CAP_GUEST_MEMFD)); - total_size = page_size * 4;
fd = vm_create_guest_memfd(vm, total_size, flags);
test_file_read_write(fd); - test_mmap(fd, page_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_using_memory_directly_from_userspace(vm, fd, page_size); + close(fd); }
@@ -201,7 +381,10 @@ int main(int argc, char *argv[])
TEST_REQUIRE(kvm_has_cap(KVM_CAP_GUEST_MEMFD));
- vm = vm_create_barebones(); + if ((kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM))) + vm = vm_create_barebones_type(KVM_X86_SW_PROTECTED_VM); + else + vm = vm_create_barebones();
test_create_guest_memfd_invalid(vm); test_create_guest_memfd_multiple(vm);