linux-kernel - Re: [PATCH 0/2] iommu/amd: Fix IOMMUv2 devices when SME is active

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Message-ID: <34db343f-cd23-09af-3bc5-29b9d385f85d@amd.com>
Date:   Wed, 26 Aug 2020 11:22:01 -0400
From:   Felix Kuehling <felix.kuehling@....com>
To:     "Deucher, Alexander" <Alexander.Deucher@....com>,
        Joerg Roedel <joro@...tes.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "Huang, Ray" <ray.huang@....com>
Cc:     "jroedel@...e.de" <jroedel@...e.de>,
        "Lendacky, Thomas" <Thomas.Lendacky@....com>,
        "Suthikulpanit, Suravee" <Suravee.Suthikulpanit@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/2] iommu/amd: Fix IOMMUv2 devices when SME is active

[+Ray]


Thanks for the heads up. Currently KFD won't work on APUs when IOMMUv2
is disabled. But Ray is working on fallbacks that will allow KFD to work
on APUs even without IOMMUv2, similar to our dGPUs. Along with changes
in ROCm user mode, those fallbacks are necessary for making ROCm on APUs
generally useful.


How common is SME on typical PCs or laptops that would use AMD APUs?


Alex, do you know if anyone has tested amdgpu on an APU with SME
enabled? Is this considered something we support?


Thanks,
  Felix


Am 2020-08-26 um 10:14 a.m. schrieb Deucher, Alexander:
>
> [AMD Official Use Only - Internal Distribution Only]
>
>
> + Felix
> ------------------------------------------------------------------------
> *From:* Joerg Roedel <joro@...tes.org>
> *Sent:* Monday, August 24, 2020 6:54 AM
> *To:* iommu@...ts.linux-foundation.org <iommu@...ts.linux-foundation.org>
> *Cc:* Joerg Roedel <joro@...tes.org>; jroedel@...e.de
> <jroedel@...e.de>; Lendacky, Thomas <Thomas.Lendacky@....com>;
> Suthikulpanit, Suravee <Suravee.Suthikulpanit@....com>; Deucher,
> Alexander <Alexander.Deucher@....com>; linux-kernel@...r.kernel.org
> <linux-kernel@...r.kernel.org>
> *Subject:* [PATCH 0/2] iommu/amd: Fix IOMMUv2 devices when SME is active
>  
> From: Joerg Roedel <jroedel@...e.de>
>
> Hi,
>
> Some IOMMUv2 capable devices do not work correctly when SME is
> active, because their DMA mask does not include the encryption bit, so
> that they can not DMA to encrypted memory directly.
>
> The IOMMU can jump in here, but the AMD IOMMU driver puts IOMMUv2
> capable devices into an identity mapped domain. Fix that by not
> forcing an identity mapped domain on devices when SME is active and
> forbid using their IOMMUv2 functionality.
>
> Please review.
>
> Thanks,
>
>         Joerg
>
> Joerg Roedel (2):
>   iommu/amd: Do not force direct mapping when SME is active
>   iommu/amd: Do not use IOMMUv2 functionality when SME is active
>
>  drivers/iommu/amd/iommu.c    | 7 ++++++-
>  drivers/iommu/amd/iommu_v2.c | 7 +++++++
>  2 files changed, 13 insertions(+), 1 deletion(-)
>
> -- 
> 2.28.0
>