Re: [PATCH v7 9/9] KVM: guest_memfd: selftests: guest_memfd mmap() test when mapping is allowed

[Fuad Tabba <tabba@google.com>]

Hi Ackerley,

On Tue, 1 Apr 2025 at 18:25, Ackerley Tng <ackerleytng@google.com> wrote:
>
> Fuad Tabba <tabba@google.com> writes:
>
> > Expand the guest_memfd selftests to include testing mapping guest
> > memory for VM types that support it.
> >
> > Also, build the guest_memfd selftest for arm64.
> >
> > Signed-off-by: Fuad Tabba <tabba@google.com>
> > ---
> >  tools/testing/selftests/kvm/Makefile.kvm      |  1 +
> >  .../testing/selftests/kvm/guest_memfd_test.c  | 75 +++++++++++++++++--
> >  2 files changed, 70 insertions(+), 6 deletions(-)
> >
> > diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
> > index 4277b983cace..c9a3f30e28dd 100644
> > --- a/tools/testing/selftests/kvm/Makefile.kvm
> > +++ b/tools/testing/selftests/kvm/Makefile.kvm
> > @@ -160,6 +160,7 @@ TEST_GEN_PROGS_arm64 += coalesced_io_test
> >  TEST_GEN_PROGS_arm64 += demand_paging_test
> >  TEST_GEN_PROGS_arm64 += dirty_log_test
> >  TEST_GEN_PROGS_arm64 += dirty_log_perf_test
> > +TEST_GEN_PROGS_arm64 += guest_memfd_test
> >  TEST_GEN_PROGS_arm64 += guest_print_test
> >  TEST_GEN_PROGS_arm64 += get-reg-list
> >  TEST_GEN_PROGS_arm64 += kvm_create_max_vcpus
> > diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
> > index ce687f8d248f..38c501e49e0e 100644
> > --- a/tools/testing/selftests/kvm/guest_memfd_test.c
> > +++ b/tools/testing/selftests/kvm/guest_memfd_test.c
> > @@ -34,12 +34,48 @@ 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_allowed(int fd, size_t total_size)
> >  {
> > +     size_t page_size = getpagesize();
> > +     const char val = 0xaa;
> > +     char *mem;
> > +     int ret;
> > +     int i;
>
> Was using this test with hugetlb patches - int i was overflowing and
> causing test failures.  Perhaps use size_t i for this instead?

I need to think big, or rather, huge (sorry :)) . Will fix this.

Cheers,
/fuad

> > +
> > +     mem = mmap(NULL, total_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
> > +     TEST_ASSERT(mem != MAP_FAILED, "mmaping() guest memory should pass.");
> > +
> > +     memset(mem, val, total_size);
> > +     for (i = 0; i < total_size; i++)
> > +             TEST_ASSERT_EQ(mem[i], val);
> > +
> > +     ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0,
> > +                     page_size);
> > +     TEST_ASSERT(!ret, "fallocate the first page should succeed");
> > +
> > +     for (i = 0; i < page_size; i++)
> > +             TEST_ASSERT_EQ(mem[i], 0x00);
> > +     for (; i < total_size; i++)
> > +             TEST_ASSERT_EQ(mem[i], val);
> > +
> > +     memset(mem, val, total_size);
> > +     for (i = 0; i < total_size; i++)
> > +             TEST_ASSERT_EQ(mem[i], val);
> > +
> > +     ret = munmap(mem, total_size);
> > +     TEST_ASSERT(!ret, "munmap should succeed");
> > +}
> > +
> > +static void test_mmap_denied(int fd, size_t total_size)
> > +{
> > +     size_t page_size = getpagesize();
> >       char *mem;
> >
> >       mem = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
> >       TEST_ASSERT_EQ(mem, MAP_FAILED);
> > +
> > +     mem = mmap(NULL, total_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)
> > @@ -170,19 +206,27 @@ static void test_create_guest_memfd_multiple(struct kvm_vm *vm)
> >       close(fd1);
> >  }
> >
> > -int main(int argc, char *argv[])
> > +unsigned long get_shared_type(void)
> >  {
> > -     size_t page_size;
> > +#ifdef __x86_64__
> > +     return KVM_X86_SW_PROTECTED_VM;
> > +#endif
> > +     return 0;
> > +}
> > +
> > +void test_vm_type(unsigned long type, bool is_shared)
> > +{
> > +     struct kvm_vm *vm;
> >       size_t total_size;
> > +     size_t page_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();
> > +     vm = vm_create_barebones_type(type);
> >
> >       test_create_guest_memfd_invalid(vm);
> >       test_create_guest_memfd_multiple(vm);
> > @@ -190,10 +234,29 @@ int main(int argc, char *argv[])
> >       fd = vm_create_guest_memfd(vm, total_size, 0);
> >
> >       test_file_read_write(fd);
> > -     test_mmap(fd, page_size);
> > +
> > +     if (is_shared)
> > +             test_mmap_allowed(fd, total_size);
> > +     else
> > +             test_mmap_denied(fd, total_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);
> > +     kvm_vm_release(vm);
> > +}
> > +
> > +int main(int argc, char *argv[])
> > +{
> > +#ifndef __aarch64__
> > +     /* For now, arm64 only supports shared guest memory. */
> > +     test_vm_type(VM_TYPE_DEFAULT, false);
> > +#endif
> > +
> > +     if (kvm_has_cap(KVM_CAP_GMEM_SHARED_MEM))
> > +             test_vm_type(get_shared_type(), true);
> > +
> > +     return 0;
> >  }