Re: [PATCH 02/15] KVM: selftests: Expose align() helpers to tests

[Ben Gardon]

On Wed, Feb 10, 2021 at 3:06 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> Refactor align() to work with non-pointers, add align_ptr() for use with
> pointers, and expose both helpers so that they can be used by tests
> and/or other utilities.  The align() helper in particular will be used
> to ensure gpa alignment for hugepages.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>

Reviewed-by: Ben Gardon <bgardon@xxxxxxxxxx>

> ---
>  tools/testing/selftests/kvm/include/kvm_util.h | 15 +++++++++++++++
>  tools/testing/selftests/kvm/lib/kvm_util.c     | 11 +----------
>  2 files changed, 16 insertions(+), 10 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
> index 2d7eb6989e83..4b5d2362a68a 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util.h
> +++ b/tools/testing/selftests/kvm/include/kvm_util.h
> @@ -79,6 +79,21 @@ struct vm_guest_mode_params {
>  };
>  extern const struct vm_guest_mode_params vm_guest_mode_params[];
>
> +/* Aligns x up to the next multiple of size. Size must be a power of 2. */

It might also be worth updating this comment to clarify that the
function rounds down, not up.

> +static inline uint64_t align(uint64_t x, uint64_t size)
> +{
> +       uint64_t mask = size - 1;
> +
> +       TEST_ASSERT(size != 0 && !(size & (size - 1)),
> +                   "size not a power of 2: %lu", size);
> +       return ((x + mask) & ~mask);
> +}
> +
> +static inline void *align_ptr(void *x, size_t size)
> +{
> +       return (void *)align((unsigned long)x, size);
> +}
> +
>  int kvm_check_cap(long cap);
>  int vm_enable_cap(struct kvm_vm *vm, struct kvm_enable_cap *cap);
>  int vcpu_enable_cap(struct kvm_vm *vm, uint32_t vcpu_id,
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index 960f4c5129ff..584167c6dbc7 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -21,15 +21,6 @@
>  #define KVM_UTIL_PGS_PER_HUGEPG 512
>  #define KVM_UTIL_MIN_PFN       2
>
> -/* Aligns x up to the next multiple of size. Size must be a power of 2. */
> -static void *align(void *x, size_t size)
> -{
> -       size_t mask = size - 1;
> -       TEST_ASSERT(size != 0 && !(size & (size - 1)),
> -                   "size not a power of 2: %lu", size);
> -       return (void *) (((size_t) x + mask) & ~mask);
> -}
> -
>  /*
>   * Capability
>   *
> @@ -757,7 +748,7 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
>                     region->mmap_start, errno);
>
>         /* Align host address */
> -       region->host_mem = align(region->mmap_start, alignment);
> +       region->host_mem = align_ptr(region->mmap_start, alignment);
>
>         /* As needed perform madvise */
>         if (src_type == VM_MEM_SRC_ANONYMOUS || src_type == VM_MEM_SRC_ANONYMOUS_THP) {
> --
> 2.30.0.478.g8a0d178c01-goog
>