Re: [PATCH v2 5/5] KVM: selftests: test userfaultfd minor for guest_memfd

* Mike Rapoport rppt@kernel.org [251125 13:39]:

From: Nikita Kalyazin kalyazin@amazon.com

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 Co-developed-by: Mike Rapoport (Microsoft) rppt@kernel.org Signed-off-by: Mike Rapoport (Microsoft) rppt@kernel.org

Acked-by: Liam R. Howlett Liam.Howlett@oracle.com

---

.../testing/selftests/kvm/guest_memfd_test.c | 103 ++++++++++++++++++ 1 file changed, 103 insertions(+)

diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c index e7d9aeb418d3..a5d3ed21d7bb 100644 --- a/tools/testing/selftests/kvm/guest_memfd_test.c +++ b/tools/testing/selftests/kvm/guest_memfd_test.c @@ -10,13 +10,17 @@ #include <errno.h> #include <stdio.h> #include <fcntl.h> +#include <pthread.h> #include <linux/bitmap.h> #include <linux/falloc.h> #include <linux/sizes.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" @@ -254,6 +258,104 @@ static void test_guest_memfd_flags(struct kvm_vm *vm) } } +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 total_size) +{

• struct uffdio_api uffdio_api = {

• .api = UFFD_API,
  

• .features = UFFD_FEATURE_MINOR_GENERIC,
  

• };
• 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);
• memset(buf, 0xaa, total_size);
• uffd = syscall(__NR_userfaultfd, O_CLOEXEC);
• TEST_ASSERT(uffd != -1, "userfaultfd creation should succeed");
• 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");
• /*

• * wait for fault_thread to finish to make sure fault happened and was
  

• * resolved before we verify the values
  

• */
  

• ret = pthread_join(fault_thread, NULL);
• TEST_ASSERT(ret == 0, "pthread_join 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 = 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);

+}

#define gmem_test(__test, __vm, __flags) \ do { \ int fd = vm_create_guest_memfd(__vm, page_size * 4, __flags); \ @@ -273,6 +375,7 @@ static void __test_guest_memfd(struct kvm_vm *vm, uint64_t flags) if (flags & GUEST_MEMFD_FLAG_INIT_SHARED) { gmem_test(mmap_supported, vm, flags); gmem_test(fault_overflow, vm, flags);

• 	gmem_test(uffd_minor, vm, flags);
  

  } else { gmem_test(fault_private, vm, flags); }

-- 2.50.1