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

On Thu, Jul 17, 2025 at 07:45:51PM -0700, Nicolin Chen wrote:

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.

I realized that we can't change the number as it won't reproduce on PAGE_SIZE=4K. So, perhaps it should just SKIP other page sizes than 4K.

Thanks Nicolin