Re: [PATCH 32/34] KVM: selftests: Add basic selftest for guest_memfd()

[Fuad Tabba <tabba@google.com>]

Hi,

On Sun, Nov 5, 2023 at 4:35 PM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> From: Chao Peng <chao.p.peng@linux.intel.com>
>
> Add a selftest to verify the basic functionality of guest_memfd():
>
> + file descriptor created with the guest_memfd() ioctl does not allow
>   read/write/mmap operations
> + file size and block size as returned from fstat are as expected
> + fallocate on the fd checks that offset/length on
>   fallocate(FALLOC_FL_PUNCH_HOLE) should be page aligned
> + invalid inputs (misaligned size, invalid flags) are rejected
> + file size and inode are unique (the innocuous-sounding
>   anon_inode_getfile() backs all files with a single inode...)
>
> Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
> Co-developed-by: Ackerley Tng <ackerleytng@google.com>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>
> Co-developed-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> Co-developed-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> Message-Id: <20231027182217.3615211-35-seanjc@google.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  tools/testing/selftests/kvm/Makefile          |   1 +
>  .../testing/selftests/kvm/guest_memfd_test.c  | 206 ++++++++++++++++++
>  2 files changed, 207 insertions(+)
>  create mode 100644 tools/testing/selftests/kvm/guest_memfd_test.c
>
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index ecdea5e7afa8..fd3b30a4ca7b 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -134,6 +134,7 @@ TEST_GEN_PROGS_x86_64 += access_tracking_perf_test
>  TEST_GEN_PROGS_x86_64 += demand_paging_test
>  TEST_GEN_PROGS_x86_64 += dirty_log_test
>  TEST_GEN_PROGS_x86_64 += dirty_log_perf_test
> +TEST_GEN_PROGS_x86_64 += guest_memfd_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_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
> new file mode 100644
> index 000000000000..ea0ae7e25330
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/guest_memfd_test.c
> @@ -0,0 +1,206 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright Intel Corporation, 2023
> + *
> + * Author: Chao Peng <chao.p.peng@linux.intel.com>
> + */
> +
> +#define _GNU_SOURCE
> +#include "test_util.h"
> +#include "kvm_util_base.h"
> +#include <linux/bitmap.h>
> +#include <linux/falloc.h>
> +#include <sys/mman.h>
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +
> +#include <stdlib.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include <errno.h>
> +#include <stdio.h>
> +#include <fcntl.h>

The include ordering should be fixed. Otherwise,

Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com>

Cheers,
/fuad


> +
> +static void test_file_read_write(int fd)
> +{
> +       char buf[64];
> +
> +       TEST_ASSERT(read(fd, buf, sizeof(buf)) < 0,
> +                   "read on a guest_mem fd should fail");
> +       TEST_ASSERT(write(fd, buf, sizeof(buf)) < 0,
> +                   "write on a guest_mem fd should fail");
> +       TEST_ASSERT(pread(fd, buf, sizeof(buf), 0) < 0,
> +                   "pread on a guest_mem fd should fail");
> +       TEST_ASSERT(pwrite(fd, buf, sizeof(buf), 0) < 0,
> +                   "pwrite on a guest_mem fd should fail");
> +}
> +
> +static void test_mmap(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);
> +}
> +
> +static void test_file_size(int fd, size_t page_size, size_t total_size)
> +{
> +       struct stat sb;
> +       int ret;
> +
> +       ret = fstat(fd, &sb);
> +       TEST_ASSERT(!ret, "fstat should succeed");
> +       TEST_ASSERT_EQ(sb.st_size, total_size);
> +       TEST_ASSERT_EQ(sb.st_blksize, page_size);
> +}
> +
> +static void test_fallocate(int fd, size_t page_size, size_t total_size)
> +{
> +       int ret;
> +
> +       ret = fallocate(fd, FALLOC_FL_KEEP_SIZE, 0, total_size);
> +       TEST_ASSERT(!ret, "fallocate with aligned offset and size should succeed");
> +
> +       ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
> +                       page_size - 1, page_size);
> +       TEST_ASSERT(ret, "fallocate with unaligned offset should fail");
> +
> +       ret = fallocate(fd, FALLOC_FL_KEEP_SIZE, total_size, page_size);
> +       TEST_ASSERT(ret, "fallocate beginning at total_size should fail");
> +
> +       ret = fallocate(fd, FALLOC_FL_KEEP_SIZE, total_size + page_size, page_size);
> +       TEST_ASSERT(ret, "fallocate beginning after total_size should fail");
> +
> +       ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
> +                       total_size, page_size);
> +       TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) at total_size should succeed");
> +
> +       ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
> +                       total_size + page_size, page_size);
> +       TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) after total_size should succeed");
> +
> +       ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
> +                       page_size, page_size - 1);
> +       TEST_ASSERT(ret, "fallocate with unaligned size should fail");
> +
> +       ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
> +                       page_size, page_size);
> +       TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) with aligned offset and size should succeed");
> +
> +       ret = fallocate(fd, FALLOC_FL_KEEP_SIZE, page_size, page_size);
> +       TEST_ASSERT(!ret, "fallocate to restore punched hole should succeed");
> +}
> +
> +static void test_invalid_punch_hole(int fd, size_t page_size, size_t total_size)
> +{
> +       struct {
> +               off_t offset;
> +               off_t len;
> +       } testcases[] = {
> +               {0, 1},
> +               {0, page_size - 1},
> +               {0, page_size + 1},
> +
> +               {1, 1},
> +               {1, page_size - 1},
> +               {1, page_size},
> +               {1, page_size + 1},
> +
> +               {page_size, 1},
> +               {page_size, page_size - 1},
> +               {page_size, page_size + 1},
> +       };
> +       int ret, i;
> +
> +       for (i = 0; i < ARRAY_SIZE(testcases); i++) {
> +               ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
> +                               testcases[i].offset, testcases[i].len);
> +               TEST_ASSERT(ret == -1 && errno == EINVAL,
> +                           "PUNCH_HOLE with !PAGE_SIZE offset (%lx) and/or length (%lx) should fail",
> +                           testcases[i].offset, testcases[i].len);
> +       }
> +}
> +
> +static void test_create_guest_memfd_invalid(struct kvm_vm *vm)
> +{
> +       size_t page_size = getpagesize();
> +       uint64_t flag;
> +       size_t size;
> +       int fd;
> +
> +       for (size = 1; size < page_size; size++) {
> +               fd = __vm_create_guest_memfd(vm, size, 0);
> +               TEST_ASSERT(fd == -1 && errno == EINVAL,
> +                           "guest_memfd() with non-page-aligned page size '0x%lx' should fail with EINVAL",
> +                           size);
> +       }
> +
> +       for (flag = 1; flag; flag <<= 1) {
> +               uint64_t bit;
> +
> +               fd = __vm_create_guest_memfd(vm, page_size, flag);
> +               TEST_ASSERT(fd == -1 && errno == EINVAL,
> +                           "guest_memfd() with flag '0x%lx' should fail with EINVAL",
> +                           flag);
> +
> +               for_each_set_bit(bit, &valid_flags, 64) {
> +                       fd = __vm_create_guest_memfd(vm, page_size, flag | BIT_ULL(bit));
> +                       TEST_ASSERT(fd == -1 && errno == EINVAL,
> +                                   "guest_memfd() with flags '0x%llx' should fail with EINVAL",
> +                                   flag | BIT_ULL(bit));
> +               }
> +       }
> +}
> +
> +static void test_create_guest_memfd_multiple(struct kvm_vm *vm)
> +{
> +       int fd1, fd2, ret;
> +       struct stat st1, st2;
> +
> +       fd1 = __vm_create_guest_memfd(vm, 4096, 0);
> +       TEST_ASSERT(fd1 != -1, "memfd creation should succeed");
> +
> +       ret = fstat(fd1, &st1);
> +       TEST_ASSERT(ret != -1, "memfd fstat should succeed");
> +       TEST_ASSERT(st1.st_size == 4096, "memfd st_size should match requested size");
> +
> +       fd2 = __vm_create_guest_memfd(vm, 8192, 0);
> +       TEST_ASSERT(fd2 != -1, "memfd creation should succeed");
> +
> +       ret = fstat(fd2, &st2);
> +       TEST_ASSERT(ret != -1, "memfd fstat should succeed");
> +       TEST_ASSERT(st2.st_size == 8192, "second memfd st_size should match requested size");
> +
> +       ret = fstat(fd1, &st1);
> +       TEST_ASSERT(ret != -1, "memfd fstat should succeed");
> +       TEST_ASSERT(st1.st_size == 4096, "first memfd st_size should still match requested size");
> +       TEST_ASSERT(st1.st_ino != st2.st_ino, "different memfd should have different inode numbers");
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +       size_t page_size;
> +       size_t total_size;
> +       int fd;
> +       struct kvm_vm *vm;
> +
> +       TEST_REQUIRE(kvm_has_cap(KVM_CAP_GUEST_MEMFD));
> +
> +       page_size = getpagesize();
> +       total_size = page_size * 4;
> +
> +       vm = vm_create_barebones();
> +
> +       test_create_guest_memfd_invalid(vm);
> +       test_create_guest_memfd_multiple(vm);
> +
> +       fd = vm_create_guest_memfd(vm, total_size, 0);
> +
> +       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);
> +
> +       close(fd);
> +}
> --
> 2.39.1
>
>