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Date:   Fri, 2 Sep 2022 15:10:17 -0700
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Subject: Re: amd iommu configuration
To:     Steven J Abner <pheonix.sja@att.net>, linux-kernel@vger.kernel.org
References: <KONJHR.T3DS4EBAXDVX1.ref@att.net> <KONJHR.T3DS4EBAXDVX1@att.net>
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From:   Randy Dunlap <rdunlap@infradead.org>
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On 9/1/22 11:36, Steven J Abner wrote:
> Hi
> Building a kernel tailored for AMD 2400g on ASRock B450 using 5.18.12 as base.
> I stumbled across an odd situation and which lacked Kconfig info and lead to oddity.
> /drivers/iommu/amd/Kconfig states 'config AMD_IOMMU_V2' is 'tristate' but unlike many
> other tristate configures doesn't mention that module name is 'iommu_v2.ko' and loading should be done by adding to modules-load.d.
> 
> The oddity is that by loading as module is as follows (differences):
> 
> builtin iommu_v2 version dmesg:
> amdgpu: HMM registered 2048MB device memory
> amdgpu: Topology: Add APU node [0x0:0x0]
> amdgpu: Topology: Add APU node [0x15dd:0x1002]
> AMD-Vi: AMD IOMMUv2 loaded and initialized
> kfd kfd: amdgpu: added device 1002:15dd
> kfd kfd: amdgpu: Allocated 3969056 bytes on gart
> memmap_init_zone_device initialised 524288 pages in 0ms
> 
> module not loaded due to missing iommu.conf dmesg:
> amdgpu: CRAT table disabled by module option
> amdgpu: Topology: Add CPU node
> amdgpu: Virtual CRAT table created for CPU
> kfd kfd: amdgpu: GC IP 090100 not supported in kfd
> 
> module load through iommu.conf dmesg:
> amdgpu: CRAT table disabled by module option
> amdgpu: Topology: Add CPU node
> amdgpu: Virtual CRAT table created for CPU
> AMD-Vi: AMD IOMMUv2 loaded and initialized
> kfd kfd: amdgpu: GC IP 090100 not supported in kfd
> 
> Note, only difference on witk/without iommu.conf is:
> AMD-Vi: AMD IOMMUv2 loaded and initialized
> 
> So does this mean missing features by not having builtin?
> If not, should Kconfig have hint about module and loading?
> 
> Steve
> 
> I wish to be personally CC'ed the answers/comments posted to the list
> in response to my posting, please:) Not a list member.

Hi,
Please try these email addresses:

AMD IOMMU (AMD-VI)
M:	Joerg Roedel <joro@8bytes.org>
R:	Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
L:	iommu@lists.linux.dev

Thanks.

-- 
~Randy