linux-kernel - Re: [PATCH] drm/amdkfd: fix build error with missing AMD_IOMMU

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Message-ID: <92a6c999-c20a-2311-4e31-209a2d9229ed@amd.com>
Date:   Mon, 8 Mar 2021 14:09:53 -0500
From:   Felix Kuehling <felix.kuehling@....com>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Oded Gabbay <oded.gabbay@...il.com>,
        Colin Ian King <colin.king@...onical.com>,
        Philip Yang <philip.yang@....com>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/amdkfd: fix build error with missing AMD_IOMMU_V2

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@....com> 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.

Regards,
  Felix


>
>         Arnd