On Thu, Jun 12, 2025 at 12:03:14PM -0700, Nicolin Chen wrote:
> 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?
I expect munmap won't work with the wrong size and the test will OOM?
You'd be better to correct the actual variant->buffer_size..
Jason
