Re: [PATCH v4 09/14] selftests: harness: Move teardown conditional into test metadata

[Jason Gunthorpe]

On Thu, Jun 12, 2025 at 11:53:24AM -0700, Nicolin Chen wrote:
> @@ -2022,7 +2023,19 @@ FIXTURE_SETUP(iommufd_dirty_tracking)
>         self->fd = open("/dev/iommu", O_RDWR);
>         ASSERT_NE(-1, self->fd);
> 
> -       rc = posix_memalign(&self->buffer, HUGEPAGE_SIZE, variant->buffer_size);
> +       if (variant->hugepages) {
> +               /*
> +                * Allocation must be aligned to the HUGEPAGE_SIZE, because the
> +                * following mmap() will automatically align the length to be a
> +                * multiple of the underlying huge page size. Failing to do the
> +                * same at this allocation will result in a memory overwrite by
> +                * the mmap().
> +                */
> +               size = __ALIGN_KERNEL(variant->buffer_size, HUGEPAGE_SIZE);
> +       } else {
> +               size = variant->buffer_size;
> +       }
> +       rc = posix_memalign(&self->buffer, HUGEPAGE_SIZE, size);
>         if (rc || !self->buffer) {
>                 SKIP(return, "Skipping buffer_size=%lu due to errno=%d",
>                            variant->buffer_size, rc);
> 
> It can just upsize the allocation, i.e. the test case will only
> use the first 64M or 128MB out of the reserved 512MB huge page.

The MAP_HUGETLBFS is required that is the whole point of what it is
doing..

Jason