Re: [PATCH 2/2] iommufd/selftest: Test reserved regions near ULONG_MAX

[Nicolin Chen <nicolinc@nvidia.com>]

On Thu, Jul 17, 2025 at 04:15:09PM -0300, Jason Gunthorpe wrote:

> +TEST_F(iommufd_ioas, reserved_overflow)
> +{
> +	struct iommu_test_cmd test_cmd = {
> +		.size = sizeof(test_cmd),
> +		.op = IOMMU_TEST_OP_ADD_RESERVED,
> +		.id = self->ioas_id,
> +		.add_reserved = { .start = 6,
> +				  .length = 0xffffffffffff8001 },
> +	};
> +	__u64 iova;
> +
> +	ASSERT_EQ(0,
> +		  ioctl(self->fd, _IOMMU_TEST_CMD(IOMMU_TEST_OP_ADD_RESERVED),
> +			&test_cmd));
> +	test_err_ioctl_ioas_map(ENOSPC, buffer, 0x5000, &iova);

When:
PAGE_SIZE=SZ_64K = 0x10000
MOCK_PAGE_SIZE = PAGE_SIZE / 2 = 0x8000

This likely fails the alignment test, returning -EINVAL instead:

# iommufd.c:988:reserved_overflow:Expected 28 (28) == errno (22)
# reserved_overflow: Test failed
#          FAIL  iommufd_ioas.mock_domain_limit.reserved_overflow

So, I think we'd have to pick a number aligned to MOCK_PAGE_SIZE?
e.g. changing to 0x18000 for example can pass.

Thanks
Nicolin