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

[Jason Gunthorpe <jgg@nvidia.com>]

On Fri, Jul 18, 2025 at 11:50:30AM -0700, Nicolin Chen wrote:

> 0xfffffffffff80001 and 0x50000 could repro with 64K pages,
> exactly what your math works :)

Okay, I was also worried we'd get into trouble with how iova_alignment
might be working but if it's fine lets do this then:

@@ -975,18 +975,24 @@ TEST_F(iommufd_ioas, reserved_overflow)
                .size = sizeof(test_cmd),
                .op = IOMMU_TEST_OP_ADD_RESERVED,
                .id = self->ioas_id,
-               .add_reserved = { .start = 6,
-                                 .length = 0xffffffffffff8001 },
+               .add_reserved.start = 6,
        };
+       unsigned int map_len;
        __u64 iova;
 
-       if (PAGE_SIZE != 4096)
-               SKIP(return, "Test requires 4k PAGE_SIZE");
+       if (PAGE_SIZE == 4096) {
+               test_cmd.add_reserved.length = 0xffffffffffff8001;
+               map_len = 0x5000;
+       } else {
+               test_cmd.add_reserved.length =
+                       0xffffffffffffffff - MOCK_PAGE_SIZE * 16;
+               map_len = MOCK_PAGE_SIZE * 10;
+       }
 
        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);
+       test_err_ioctl_ioas_map(ENOSPC, buffer, map_len, &iova);
 }
 
 TEST_F(iommufd_ioas, area_allowed)

Thanks,
Jason