Re: [PATCH v2 06/10] KVM: selftests: refactor vm_mem_backing_src_type flags

[Ben Gardon]

On Wed, May 19, 2021 at 1:04 PM Axel Rasmussen <axelrasmussen@xxxxxxxxxx> wrote:
>
> Each struct vm_mem_backing_src_alias has a flags field, which denotes
> the flags used to mmap() an area of that type. Previously, this field
> never included MAP_PRIVATE | MAP_ANONYMOUS, because
> vm_userspace_mem_region_add assumed that *all* types would always use
> those flags, and so it hardcoded them.
>
> In a follow-up commit, we'll add a new type: shmem. Areas of this type
> must not have MAP_PRIVATE | MAP_ANONYMOUS, and instead they must have
> MAP_SHARED.
>
> So, refactor things. Make it so that the flags field of
> struct vm_mem_backing_src_alias really is a complete set of flags, and
> don't add in any extras in vm_userspace_mem_region_add. This will let us
> easily tack on shmem.
>
> Signed-off-by: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
> ---
>  tools/testing/selftests/kvm/lib/kvm_util.c  |  5 ++-
>  tools/testing/selftests/kvm/lib/test_util.c | 35 +++++++++++----------
>  2 files changed, 21 insertions(+), 19 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index 0d6ddee429b9..bc405785ac8b 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -759,9 +759,8 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
>
>         region->mmap_start = mmap(NULL, region->mmap_size,
>                                   PROT_READ | PROT_WRITE,
> -                                 MAP_PRIVATE | MAP_ANONYMOUS
> -                                 | vm_mem_backing_src_alias(src_type)->flag,
> -                                 -1, 0);
> +                                 vm_mem_backing_src_alias(src_type)->flag,
> +                                 region->fd, 0);

I don't see the region->fd change mentioned in the patch description
or elsewhere in this patch. Is something setting region->fd to -1 or
should this be part of another patch in the series?

>         TEST_ASSERT(region->mmap_start != MAP_FAILED,
>                     "test_malloc failed, mmap_start: %p errno: %i",
>                     region->mmap_start, errno);
> diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
> index 63d2bc7d757b..06ddde068736 100644
> --- a/tools/testing/selftests/kvm/lib/test_util.c
> +++ b/tools/testing/selftests/kvm/lib/test_util.c
> @@ -168,70 +168,73 @@ size_t get_def_hugetlb_pagesz(void)
>
>  const struct vm_mem_backing_src_alias *vm_mem_backing_src_alias(uint32_t i)
>  {
> +       static const int anon_flags = MAP_PRIVATE | MAP_ANONYMOUS;
> +       static const int anon_huge_flags = anon_flags | MAP_HUGETLB;
> +
>         static const struct vm_mem_backing_src_alias aliases[] = {
>                 [VM_MEM_SRC_ANONYMOUS] = {
>                         .name = "anonymous",
> -                       .flag = 0,
> +                       .flag = anon_flags,
>                 },
>                 [VM_MEM_SRC_ANONYMOUS_THP] = {
>                         .name = "anonymous_thp",
> -                       .flag = 0,
> +                       .flag = anon_flags,
>                 },
>                 [VM_MEM_SRC_ANONYMOUS_HUGETLB] = {
>                         .name = "anonymous_hugetlb",
> -                       .flag = MAP_HUGETLB,
> +                       .flag = anon_huge_flags,
>                 },
>                 [VM_MEM_SRC_ANONYMOUS_HUGETLB_16KB] = {
>                         .name = "anonymous_hugetlb_16kb",
> -                       .flag = MAP_HUGETLB | MAP_HUGE_16KB,
> +                       .flag = anon_huge_flags | MAP_HUGE_16KB,
>                 },
>                 [VM_MEM_SRC_ANONYMOUS_HUGETLB_64KB] = {
>                         .name = "anonymous_hugetlb_64kb",
> -                       .flag = MAP_HUGETLB | MAP_HUGE_64KB,
> +                       .flag = anon_huge_flags | MAP_HUGE_64KB,
>                 },
>                 [VM_MEM_SRC_ANONYMOUS_HUGETLB_512KB] = {
>                         .name = "anonymous_hugetlb_512kb",
> -                       .flag = MAP_HUGETLB | MAP_HUGE_512KB,
> +                       .flag = anon_huge_flags | MAP_HUGE_512KB,
>                 },
>                 [VM_MEM_SRC_ANONYMOUS_HUGETLB_1MB] = {
>                         .name = "anonymous_hugetlb_1mb",
> -                       .flag = MAP_HUGETLB | MAP_HUGE_1MB,
> +                       .flag = anon_huge_flags | MAP_HUGE_1MB,
>                 },
>                 [VM_MEM_SRC_ANONYMOUS_HUGETLB_2MB] = {
>                         .name = "anonymous_hugetlb_2mb",
> -                       .flag = MAP_HUGETLB | MAP_HUGE_2MB,
> +                       .flag = anon_huge_flags | MAP_HUGE_2MB,
>                 },
>                 [VM_MEM_SRC_ANONYMOUS_HUGETLB_8MB] = {
>                         .name = "anonymous_hugetlb_8mb",
> -                       .flag = MAP_HUGETLB | MAP_HUGE_8MB,
> +                       .flag = anon_huge_flags | MAP_HUGE_8MB,
>                 },
>                 [VM_MEM_SRC_ANONYMOUS_HUGETLB_16MB] = {
>                         .name = "anonymous_hugetlb_16mb",
> -                       .flag = MAP_HUGETLB | MAP_HUGE_16MB,
> +                       .flag = anon_huge_flags | MAP_HUGE_16MB,
>                 },
>                 [VM_MEM_SRC_ANONYMOUS_HUGETLB_32MB] = {
>                         .name = "anonymous_hugetlb_32mb",
> -                       .flag = MAP_HUGETLB | MAP_HUGE_32MB,
> +                       .flag = anon_huge_flags | MAP_HUGE_32MB,
>                 },
>                 [VM_MEM_SRC_ANONYMOUS_HUGETLB_256MB] = {
>                         .name = "anonymous_hugetlb_256mb",
> -                       .flag = MAP_HUGETLB | MAP_HUGE_256MB,
> +                       .flag = anon_huge_flags | MAP_HUGE_256MB,
>                 },
>                 [VM_MEM_SRC_ANONYMOUS_HUGETLB_512MB] = {
>                         .name = "anonymous_hugetlb_512mb",
> -                       .flag = MAP_HUGETLB | MAP_HUGE_512MB,
> +                       .flag = anon_huge_flags | MAP_HUGE_512MB,
>                 },
>                 [VM_MEM_SRC_ANONYMOUS_HUGETLB_1GB] = {
>                         .name = "anonymous_hugetlb_1gb",
> -                       .flag = MAP_HUGETLB | MAP_HUGE_1GB,
> +                       .flag = anon_huge_flags | MAP_HUGE_1GB,
>                 },
>                 [VM_MEM_SRC_ANONYMOUS_HUGETLB_2GB] = {
>                         .name = "anonymous_hugetlb_2gb",
> -                       .flag = MAP_HUGETLB | MAP_HUGE_2GB,
> +                       .flag = anon_huge_flags | MAP_HUGE_2GB,
>                 },
>                 [VM_MEM_SRC_ANONYMOUS_HUGETLB_16GB] = {
>                         .name = "anonymous_hugetlb_16gb",
> -                       .flag = MAP_HUGETLB | MAP_HUGE_16GB,
> +                       .flag = anon_huge_flags | MAP_HUGE_16GB,
>                 },
>         };
>         _Static_assert(ARRAY_SIZE(aliases) == NUM_SRC_TYPES,
> --
> 2.31.1.751.gd2f1c929bd-goog
>