On Thu, Jun 12, 2025 at 03:56:13PM -0300, Jason Gunthorpe wrote:
> 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..
I am not quite following this.. MAP_HUGETLB will be still set.
And the underlying selftest case is using:
MOCK_HUGE_PAGE_SIZE = 512 * MOCK_IO_PAGE_SIZE
Does it matter if the underlying allocation has an overshot?
Thanks
Nicolin
