On Wed, May 12, 2021 at 2:45 PM Axel Rasmussen <axelrasmussen@xxxxxxxxxx> wrote:
>
> This lets us run the demand paging test on top of a shared
> hugetlbfs-backed area. The "shared" is key, as this allows us to
> exercise userfaultfd minor faults on hugetlbfs.
>
> Signed-off-by: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
> ---
> tools/testing/selftests/kvm/demand_paging_test.c | 6 ++++--
> tools/testing/selftests/kvm/include/test_util.h | 10 ++++++++++
> tools/testing/selftests/kvm/lib/kvm_util.c | 9 +++++++--
> tools/testing/selftests/kvm/lib/test_util.c | 6 ++++++
> 4 files changed, 27 insertions(+), 4 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c
> index ff29aaea3120..32942c9e0376 100644
> --- a/tools/testing/selftests/kvm/demand_paging_test.c
> +++ b/tools/testing/selftests/kvm/demand_paging_test.c
> @@ -502,8 +502,10 @@ int main(int argc, char *argv[])
> }
> }
>
> - TEST_ASSERT(p.uffd_mode != UFFDIO_REGISTER_MODE_MINOR || p.src_type == VM_MEM_SRC_SHMEM,
> - "userfaultfd MINOR mode requires shared memory; pick a different -t");
> + if (p.uffd_mode == UFFDIO_REGISTER_MODE_MINOR &&
> + !backing_src_is_shared(p.src_type)) {
> + TEST_FAIL("userfaultfd MINOR mode requires shared memory; pick a different -t");
> + }
>
> for_each_guest_mode(run_test, &p);
>
> diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
> index 7377f00469ef..852d6d2cc285 100644
> --- a/tools/testing/selftests/kvm/include/test_util.h
> +++ b/tools/testing/selftests/kvm/include/test_util.h
> @@ -85,9 +85,19 @@ enum vm_mem_backing_src_type {
> VM_MEM_SRC_ANONYMOUS_HUGETLB_2GB,
> VM_MEM_SRC_ANONYMOUS_HUGETLB_16GB,
> VM_MEM_SRC_SHMEM,
> + VM_MEM_SRC_SHARED_HUGETLB,
> NUM_SRC_TYPES,
> };
>
> +/*
> + * Whether or not the given source type is shared memory (as opposed to
> + * anonymous).
> + */
> +static inline bool backing_src_is_shared(enum vm_mem_backing_src_type t)
> +{
> + return t == VM_MEM_SRC_SHMEM || t == VM_MEM_SRC_SHARED_HUGETLB;
> +}
Would it make sense to check (vm_mem_backing_src_alias(t)->flag &
MAP_SHARED) == MAP_SHARED instead?
> +
> struct vm_mem_backing_src_alias {
> const char *name;
> uint32_t flag;
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index 838d58633f7e..fed02153c919 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -756,8 +756,13 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
> region->mmap_size += alignment;
>
> region->fd = -1;
> - if (src_type == VM_MEM_SRC_SHMEM) {
> - region->fd = memfd_create("kvm_selftest", MFD_CLOEXEC);
> + if (backing_src_is_shared(src_type)) {
> + int memfd_flags = MFD_CLOEXEC;
> +
> + if (src_type == VM_MEM_SRC_SHARED_HUGETLB)
> + memfd_flags |= MFD_HUGETLB;
> +
> + region->fd = memfd_create("kvm_selftest", memfd_flags);
> TEST_ASSERT(region->fd != -1,
> "memfd_create failed, errno: %i", errno);
>
> diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
> index c7a265da5090..65fb8b43782c 100644
> --- a/tools/testing/selftests/kvm/lib/test_util.c
> +++ b/tools/testing/selftests/kvm/lib/test_util.c
> @@ -240,6 +240,11 @@ const struct vm_mem_backing_src_alias *vm_mem_backing_src_alias(uint32_t i)
> .name = "shmem",
> .flag = MAP_SHARED,
> },
> + [VM_MEM_SRC_SHARED_HUGETLB] = {
> + .name = "shared_hugetlb",
> + /* No MAP_HUGETLB, we use MFD_HUGETLB instead. */
Is it worth calling out the difference between the two flags here?
> + .flag = MAP_SHARED,
> + },
> };
> _Static_assert(ARRAY_SIZE(aliases) == NUM_SRC_TYPES,
> "Missing new backing src types?");
> @@ -262,6 +267,7 @@ size_t get_backing_src_pagesz(uint32_t i)
> case VM_MEM_SRC_ANONYMOUS_THP:
> return get_trans_hugepagesz();
> case VM_MEM_SRC_ANONYMOUS_HUGETLB:
> + case VM_MEM_SRC_SHARED_HUGETLB:
> return get_def_hugetlb_pagesz();
> default:
> return MAP_HUGE_PAGE_SIZE(flag);
> --
> 2.31.1.607.g51e8a6a459-goog
>
