The test demonstrates that a minor userfaultfd event in guest_memfd can be resolved via a memcpy followed by a UFFDIO_CONTINUE ioctl.
Signed-off-by: Nikita Kalyazin kalyazin@amazon.com --- .../testing/selftests/kvm/guest_memfd_test.c | 99 +++++++++++++++++++ 1 file changed, 99 insertions(+)
diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c index 38c501e49e0e..9a06c2486218 100644 --- a/tools/testing/selftests/kvm/guest_memfd_test.c +++ b/tools/testing/selftests/kvm/guest_memfd_test.c @@ -10,12 +10,16 @@ #include <errno.h> #include <stdio.h> #include <fcntl.h> +#include <pthread.h>
#include <linux/bitmap.h> #include <linux/falloc.h> +#include <linux/userfaultfd.h> #include <sys/mman.h> #include <sys/types.h> #include <sys/stat.h> +#include <sys/syscall.h> +#include <sys/ioctl.h>
#include "kvm_util.h" #include "test_util.h" @@ -206,6 +210,98 @@ static void test_create_guest_memfd_multiple(struct kvm_vm *vm) close(fd1); }
+struct fault_args { + char *addr; + volatile char value; +}; + +static void *fault_thread_fn(void *arg) +{ + struct fault_args *args = arg; + + /* Trigger page fault */ + args->value = *args->addr; + return NULL; +} + +static void test_uffd_minor(int fd, size_t page_size, size_t total_size) +{ + struct uffdio_register uffd_reg; + struct uffdio_continue uffd_cont; + struct uffd_msg msg; + struct fault_args args; + pthread_t fault_thread; + void *mem, *mem_nofault, *buf = NULL; + int uffd, ret; + off_t offset = page_size; + void *fault_addr; + + ret = posix_memalign(&buf, page_size, total_size); + TEST_ASSERT_EQ(ret, 0); + + uffd = syscall(__NR_userfaultfd, O_CLOEXEC); + TEST_ASSERT(uffd != -1, "userfaultfd creation should succeed"); + + struct uffdio_api uffdio_api = { + .api = UFFD_API, + .features = UFFD_FEATURE_MINOR_GUEST_MEMFD, + }; + ret = ioctl(uffd, UFFDIO_API, &uffdio_api); + TEST_ASSERT(ret != -1, "ioctl(UFFDIO_API) should succeed"); + + mem = mmap(NULL, total_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); + TEST_ASSERT(mem != MAP_FAILED, "mmap should succeed"); + + mem_nofault = mmap(NULL, total_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); + TEST_ASSERT(mem_nofault != MAP_FAILED, "mmap should succeed"); + + uffd_reg.range.start = (unsigned long)mem; + uffd_reg.range.len = total_size; + uffd_reg.mode = UFFDIO_REGISTER_MODE_MINOR; + ret = ioctl(uffd, UFFDIO_REGISTER, &uffd_reg); + TEST_ASSERT(ret != -1, "ioctl(UFFDIO_REGISTER) should succeed"); + + ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, + offset, page_size); + TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) should succeed"); + + fault_addr = mem + offset; + args.addr = fault_addr; + + ret = pthread_create(&fault_thread, NULL, fault_thread_fn, &args); + TEST_ASSERT(ret == 0, "pthread_create should succeed"); + + ret = read(uffd, &msg, sizeof(msg)); + TEST_ASSERT(ret != -1, "read from userfaultfd should succeed"); + TEST_ASSERT(msg.event == UFFD_EVENT_PAGEFAULT, "event type should be pagefault"); + TEST_ASSERT((void *)(msg.arg.pagefault.address & ~(page_size - 1)) == fault_addr, + "pagefault should occur at expected address"); + + memcpy(mem_nofault + offset, buf + offset, page_size); + + uffd_cont.range.start = (unsigned long)fault_addr; + uffd_cont.range.len = page_size; + uffd_cont.mode = 0; + ret = ioctl(uffd, UFFDIO_CONTINUE, &uffd_cont); + TEST_ASSERT(ret != -1, "ioctl(UFFDIO_CONTINUE) should succeed"); + + TEST_ASSERT(args.value == *(char *)(mem_nofault + offset), + "memory should contain the value that was copied"); + TEST_ASSERT(args.value == *(char *)(mem + offset), + "no further fault is expected"); + + ret = pthread_join(fault_thread, NULL); + TEST_ASSERT(ret == 0, "pthread_join should succeed"); + + ret = munmap(mem_nofault, total_size); + TEST_ASSERT(!ret, "munmap should succeed"); + + ret = munmap(mem, total_size); + TEST_ASSERT(!ret, "munmap should succeed"); + free(buf); + close(uffd); +} + unsigned long get_shared_type(void) { #ifdef __x86_64__ @@ -244,6 +340,9 @@ void test_vm_type(unsigned long type, bool is_shared) test_fallocate(fd, page_size, total_size); test_invalid_punch_hole(fd, page_size, total_size);
+ if (is_shared) + test_uffd_minor(fd, page_size, total_size); + close(fd); kvm_vm_release(vm); }