linux-kernel - Re: `AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y` causes AMDGPU to fail on Ryzen: amdgpu: SME is not compatible with RAVEN

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Date:   Mon, 11 Oct 2021 09:28:51 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Paul Menzel <pmenzel@...gen.mpg.de>
Cc:     Alex Deucher <alexdeucher@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, X86 ML <x86@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        amd-gfx@...ts.freedesktop.org, Borislav Petkov <bp@...en8.de>
Subject: Re: `AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y` causes AMDGPU to fail on
 Ryzen: amdgpu: SME is not compatible with RAVEN

On 10/11/21 9:21 AM, Paul Menzel wrote:
> Dear Tom,
> 
> 
> Am 11.10.21 um 15:58 schrieb Tom Lendacky:
>> On 10/11/21 8:52 AM, Paul Menzel wrote:
> 
>>> Am 11.10.21 um 15:27 schrieb Tom Lendacky:
>>>> On 10/11/21 8:11 AM, Borislav Petkov wrote:
>>>>> On Mon, Oct 11, 2021 at 03:05:33PM +0200, Paul Menzel wrote:
>>>>>> I think, the IOMMU is enabled on the MSI B350M MORTAR, but 
>>>>>> otherwise, yes
>>>>>> this looks fine. The help text could also be updated to mention 
>>>>>> problems
>>>>>> with AMD Raven devices.
>>>>>
>>>>> This is not only about Raven GPUs but, as Alex explained, pretty much
>>>>> about every device which doesn't support a 48 bit DMA mask. I'll expand
>>>>> that aspect in the changelog.
>>>>
>>>> In general, non-GPU devices that don't support a 48-bit DMA mask work 
>>>> fine (assuming they have set their DMA mask appropriately). It really 
>>>> depends on whether SWIOTLB will be able to satisfy the memory 
>>>> requirements of the driver when the IOMMU is not enabled or in 
>>>> passthrough mode. Since GPU devices need/use a lot of memory, that 
>>>> becomes a problem.
>>>
>>> How can I check that?
>>
>> How can you check what? 32-bit DMA devices? GPUs? I need a bit more 
>> information...
> 
> How can I check, why MEM_ENCRYPT is not working on my device despite the 
> IOMMU being enabled.

I believe Alex already explained that. Your original message is from commit:

ea68573d408f ("drm/amdgpu: Fail to load on RAVEN if SME is active")

Thanks,
Tom

> 
> 
> Kind regards,
> 
> Paul