Re: [PATCH] iommufd: fix selftest link dependency on amdv1 driver

[Arnd Bergmann]

On Wed, Dec 24, 2025, at 02:52, Jason Gunthorpe wrote:
> On Tue, Dec 23, 2025 at 10:51:22PM +0100, Arnd Bergmann wrote:
>> From: Arnd Bergmann <arnd@xxxxxxxx>
>> 
>> When CONFIG_AMD_IOMMU is disabled, the selftest runs into a link failure:
>> 
>> aarch64-linux-ld: drivers/iommu/iommufd/selftest.o: in function `mock_domain_alloc_pgtable.isra.0':
>> selftest.c:(.text+0x1590): undefined reference to `pt_iommu_amdv1_init'
>> aarch64-linux-ld: drivers/iommu/iommufd/selftest.o:(.rodata+0x280): undefined reference to `pt_iommu_amdv1_map_pages'
>> aarch64-linux-ld: drivers/iommu/iommufd/selftest.o:(.rodata+0x288): undefined reference to `pt_iommu_amdv1_unmap_pages'
>> aarch64-linux-ld: drivers/iommu/iommufd/selftest.o:(.rodata+0x2b0): undefined reference to `pt_iommu_amdv1_iova_to_phys'
>> aarch64-linux-ld: drivers/iommu/iommufd/selftest.o:(.rodata+0x2d8): undefined reference to `pt_iommu_amdv1_read_and_clear_dirty'
>> 
>> Change the top-level function to skip all the amdv1 tests in this
>> configuration.
>
> kconfig shouldn't let this build happen:
>
> config IOMMUFD_TEST
>         bool "IOMMU Userspace API Test support"
>         depends on DEBUG_KERNEL
>         depends on FAULT_INJECTION
>         depends on RUNTIME_TESTING_MENU
>         depends on IOMMU_PT_AMDV1
>         select IOMMUFD_DRIVER
>
> I think this is more fall out from Geert's change to make GENERIC_PT 
> unselectable, the 'depends on' is no longer enough??
>
> I guess the right fix is to add a "select GENERIC_PT" above, does that
> work for you?

No, it's already set.

The configuration that had the build failure contains

CONFIG_ARM64=y
# CONFIG_AMD_IOMMU is not set
CONFIG_GENERIC_PT=y
CONFIG_IOMMU_PT=m
CONFIG_IOMMU_PT_AMDV1=m
CONFIG_IOMMUFD=y
CONFIG_IOMMUFD_TEST=y

I suspect this is because IOMMUFD_TEST is 'bool' and can be enabled
even when its dependencies are =m, but if the test code is built-in,
it can't actually link.

This should be fixable using

       depends on IOMMU_PT_AMDV1=y || IOMMUFD=IOMMU_PT_AMDV1

or by forcing the iommufd code to be a loadable module when
IOMMU_PT_AMDV=m, e.g. through

config IOMMUFD
      depends on IOMMU_PT_AMDV1 || !IOMMU_PT_AMDV1 || !RUNTIME_TESTING_MENU

A cleaner approach might be to split out IOMMUFD_TEST into a separate
module rather than including it inside of the IOMMUFD module,
but that is likely much more work.

      Arnd