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 08:58:02 -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 8:52 AM, Paul Menzel wrote:
> Dear Tom,
> 
> 
> 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...

Thanks,
Tom

> 
> 
> Kind regards,
> 
> Paul