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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: <139ed784-d622-b0d2-3650-736b42e624f0@molgen.mpg.de>
Date:   Mon, 11 Oct 2021 15:52:14 +0200
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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?


Kind regards,

Paul