Re: [PATCH 2/2] iommu/amd: Force identity mode for selected GPUs only

Mario Limonciello <[email protected]> Tue, 28 Jul 2026 00:31:04 -0500
Newsgroups dev.linux.lists.iommu,org.kernel.vger.linux-pci
Message-ID <[email protected]>
+Felix

On 7/27/26 23:52, Vasant Hegde wrote:
> Mario,
> 
> 
> On 7/27/2026 8:15 PM, Mario Limonciello wrote:
>>
>>
>> On 7/26/26 23:19, Vasant Hegde wrote:
>>>
>>>
> 
> .../...
> 
>>>>
>>>> I think this can probably be dropped now? There is no intersection of
>>>> this old broken embedded GPU and a CPU that supports CC right?
>>>
>>>
>>> I did consider dropping these two checks, but I was not entirely sure. So I kept
>>> as is for now. Once these series settles and I can go with next step of dropping
>>> these two checks.
>>>
>>> @Alex, @Mario, Any suggestions ?
>>>
>>
>> The background comes from this series:
>>
>> https://lore.kernel.org/all/[email protected]/
> 
> 
> Thanks for old link. So it looks like we are good to drop SME check?

Yeah I think so.

> 
> Also is it safe to assume SNP is not enabled on these platform and drop that
> check? Anyway SNP requirement (which doesn't support identity mapping) and APU
> requirement (needs identity mapping) is conflicting.
> 

The current platforms I think this is a safe assumption.

Felix,

Can we revisit the requirement of identity mapping for APU?  Does it 
still hold with the current hardware and software?

I'm wondering if we can just apply it to Raven and loosen up elsewhere 
and what gives if we do that.