Am 08.03.21 um 21:02 schrieb Felix Kuehling:
Am 2021-03-08 um 2:33 p.m. schrieb Arnd Bergmann:
On Mon, Mar 8, 2021 at 8:11 PM Felix Kuehling <felix.kuehling@xxxxxxx> wrote:
Am 2021-03-08 um 2:05 p.m. schrieb Arnd Bergmann:
On Mon, Mar 8, 2021 at 5:24 PM Felix Kuehling <felix.kuehling@xxxxxxx> wrote:
The driver build should work without IOMMUv2. In amdkfd/Makefile, we
have this condition:
ifneq ($(CONFIG_AMD_IOMMU_V2),)
AMDKFD_FILES += $(AMDKFD_PATH)/kfd_iommu.o
endif
In amdkfd/kfd_iommu.h we define inline stubs of the functions that are
causing your link-failures if IOMMU_V2 is not enabled:
#if defined(CONFIG_AMD_IOMMU_V2_MODULE) || defined(CONFIG_AMD_IOMMU_V2)
... function declarations ...
#else
... stubs ...
#endif
Right, that is the problem I tried to explain in my patch description.
Should we just drop the 'imply' then and add a proper dependency like this?
depends on DRM_AMDGPU && (X86_64 || ARM64 || PPC64)
depends on AMD_IOMMU_V2=y || DRM_AMDGPU=m
I can send a v2 after some testing if you prefer this version.
No. My point is, there should not be a hard dependency. The build should
work without CONFIG_AMD_IOMMU_V2. I don't understand why it's not
working for you. It looks like you're building kfd_iommu.o, which should
not be happening when AMD_IOMMU_V2 is not enabled. The condition in
amdkfd/Makefile should make sure that kfd_iommu.o doesn't get built with
your kernel config.
Again, as I explained in the changelog text, AMD_IOMMU_V2 configured as
a loadable module, while AMDGPU is configured as built-in.
I'm sorry, I didn't read it carefully. And I thought "imply" was meant
to fix exactly this kind of issue.
I don't want to create a hard dependency on AMD_IOMMU_V2 if I can avoid
it, because it is only really needed for a small number of AMD APUs, and
even there it is now optional for more recent ones.
Is there a better way to avoid build failures without creating a hard
dependency?
What you need is the same trick we used for AGP on radeon/nouveau:
depends on AMD_IOMMU_V2 || !AMD_IOMMU_V2
This way when AMD_IOMMU_V2 is build as a module DRM_AMDGPU will be build
as a module as well. When it is disabled completely we don't care.
Regards,
Christian.
The documentation in
Documentation/kbuild/kconfig-language.rst suggests using if
(IS_REACHABLE(CONFIG_AMD_IOMMU_V2)) to guard those problematic function
calls. I think more generally, we could guard all of kfd_iommu.c with
#if IS_REACHABLE(CONFIG_AMD_IOMMU_V2)
And use the same condition to define the stubs in kfd_iommu.h.
Regards,
Felix
The causes a link failure for the vmlinux file, because the linker cannot
resolve addresses of loadable modules at compile time -- they have
not been loaded yet.
Arnd
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