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Subject: Re: `AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y` causes AMDGPU to fail on
 Ryzen: amdgpu: SME is not compatible with RAVEN
To:     Tom Lendacky <thomas.lendacky@amd.com>
Cc:     Alex Deucher <alexdeucher@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, X86 ML <x86@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        LKML <linux-kernel@vger.kernel.org>,
        amd-gfx@lists.freedesktop.org, Borislav Petkov <bp@alien8.de>
References: <8bbacd0e-4580-3194-19d2-a0ecad7df09c@molgen.mpg.de>
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From:   Paul Menzel <pmenzel@molgen.mpg.de>
Message-ID: <8b21ebbd-f7ca-8af3-5398-8320c6ed6422@molgen.mpg.de>
Date:   Mon, 11 Oct 2021 16:21:55 +0200
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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.


Kind regards,

Paul