CONFIG_GUP_TEST provides userspace with an ioctl to invoke pin_user_pages(), and this test uses the ioctl to pin pages, to check that memory attributes cannot be set to private if shared pages are pinned.
Signed-off-by: Ackerley Tng ackerleytng@google.com --- tools/testing/selftests/kvm/Makefile | 1 + .../selftests/kvm/guest_memfd_pin_test.c | 104 ++++++++++++++++++ 2 files changed, 105 insertions(+) create mode 100644 tools/testing/selftests/kvm/guest_memfd_pin_test.c
diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile index 3c1f35456bfc..c5a1c8c7125a 100644 --- a/tools/testing/selftests/kvm/Makefile +++ b/tools/testing/selftests/kvm/Makefile @@ -136,6 +136,7 @@ TEST_GEN_PROGS_x86_64 += dirty_log_perf_test TEST_GEN_PROGS_x86_64 += guest_memfd_test TEST_GEN_PROGS_x86_64 += guest_memfd_hugetlb_reporting_test TEST_GEN_PROGS_x86_64 += guest_memfd_sharing_test +TEST_GEN_PROGS_x86_64 += guest_memfd_pin_test TEST_GEN_PROGS_x86_64 += guest_print_test TEST_GEN_PROGS_x86_64 += hardware_disable_test TEST_GEN_PROGS_x86_64 += kvm_create_max_vcpus diff --git a/tools/testing/selftests/kvm/guest_memfd_pin_test.c b/tools/testing/selftests/kvm/guest_memfd_pin_test.c new file mode 100644 index 000000000000..b45fb8024970 --- /dev/null +++ b/tools/testing/selftests/kvm/guest_memfd_pin_test.c @@ -0,0 +1,104 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Test that pinned pages block KVM from setting memory attributes to PRIVATE. + * + * Copyright (c) 2024, Google LLC. + */ +#include <string.h> +#include <sys/mman.h> +#include <unistd.h> + +#include "test_util.h" +#include "kvm_util.h" +#include "../../../../mm/gup_test.h" + +#define GUEST_MEMFD_PIN_TEST_SLOT 10 +#define GUEST_MEMFD_PIN_TEST_GPA 0x50000000ULL +#define GUEST_MEMFD_PIN_TEST_OFFSET 0 + +static int gup_test_fd; + +void pin_pages(void *vaddr, uint64_t size) +{ + const struct pin_longterm_test args = { + .addr = (uint64_t)vaddr, + .size = size, + .flags = PIN_LONGTERM_TEST_FLAG_USE_WRITE, + }; + + TEST_ASSERT_EQ(ioctl(gup_test_fd, PIN_LONGTERM_TEST_START, &args), 0); +} + +void unpin_pages(void) +{ + TEST_ASSERT_EQ(ioctl(gup_test_fd, PIN_LONGTERM_TEST_STOP), 0); +} + +void run_test(void) +{ + struct kvm_vm *vm; + size_t page_size; + void *mem; + int fd; + + vm = vm_create_barebones_type(KVM_X86_SW_PROTECTED_VM); + + page_size = getpagesize(); + fd = vm_create_guest_memfd(vm, page_size, 0); + + mem = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, + GUEST_MEMFD_PIN_TEST_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. + */ + vm_set_user_memory_region2(vm, GUEST_MEMFD_PIN_TEST_SLOT, + KVM_MEM_GUEST_MEMFD, + GUEST_MEMFD_PIN_TEST_GPA, page_size, mem, fd, + GUEST_MEMFD_PIN_TEST_OFFSET); + + /* Before pinning pages, toggling memory attributes should be fine. */ + vm_mem_set_private(vm, GUEST_MEMFD_PIN_TEST_GPA, page_size); + vm_mem_set_shared(vm, GUEST_MEMFD_PIN_TEST_GPA, page_size); + + pin_pages(mem, page_size); + + /* + * Pinning also faults pages in, so remove these pages from userspace + * page tables to properly test that pinning blocks setting memory + * attributes to private. + */ + TEST_ASSERT_EQ(madvise(mem, page_size, MADV_DONTNEED), 0); + + /* Should fail since the page is still faulted in. */ + TEST_ASSERT_EQ(__vm_set_memory_attributes(vm, GUEST_MEMFD_PIN_TEST_GPA, + page_size, + KVM_MEMORY_ATTRIBUTE_PRIVATE), + -1); + TEST_ASSERT_EQ(errno, EINVAL); + + unpin_pages(); + + /* With the pages unpinned, kvm can set this page to private. */ + vm_mem_set_private(vm, GUEST_MEMFD_PIN_TEST_GPA, page_size); + + kvm_vm_free(vm); + close(fd); +} + +int main(int argc, char *argv[]) +{ + gup_test_fd = open("/sys/kernel/debug/gup_test", O_RDWR); + /* + * This test depends on CONFIG_GUP_TEST to provide a kernel module that + * exposes pin_user_pages() to userspace. + */ + TEST_REQUIRE(gup_test_fd != -1); + TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM)); + + run_test(); + + return 0; +}