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

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Message-ID: <63c70551-255f-2df9-af70-7965e80172af@amd.com>
Date:   Mon, 7 Sep 2020 13:10:17 +0200
From:   Christian König <christian.koenig@....com>
To:     Joerg Roedel <joro@...tes.org>,
        "Deucher, Alexander" <Alexander.Deucher@....com>
Cc:     "jroedel@...e.de" <jroedel@...e.de>,
        "Kuehling, Felix" <Felix.Kuehling@....com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "Huang, Ray" <Ray.Huang@....com>,
        "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

Am 07.09.20 um 12:44 schrieb Joerg Roedel:
> On Sun, Sep 06, 2020 at 04:08:58PM +0000, Deucher, Alexander wrote:
>>  From f479b9da353c2547c26ebac8930a5dcd9a134eb7 Mon Sep 17 00:00:00 2001
>> From: Alex Deucher <alexander.deucher@....com>
>> Date: Sun, 6 Sep 2020 12:05:12 -0400
>> Subject: [PATCH] drm/amdgpu: Fail to load on RAVEN if SME is active
>>
>> Due to hardware bugs, scatter/gather display on raven requires
>> a 1:1 IOMMU mapping, however, SME (System Memory Encryption)
>> requires an indirect IOMMU mapping because the encryption bit
>> is beyond the DMA mask of the chip.  As such, the two are
>> incompatible.
>>
>> Signed-off-by: Alex Deucher <alexander.deucher@....com>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 10 ++++++++++
>>   1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>> index 12e16445df7c..d87d37c25329 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>> @@ -1102,6 +1102,16 @@ static int amdgpu_pci_probe(struct pci_dev *pdev,
>>   		return -ENODEV;
>>   	}
>>   
>> +	/* Due to hardware bugs, S/G Display on raven requires a 1:1 IOMMU mapping,
>> +	 * however, SME requires an indirect IOMMU mapping because the encryption
>> +	 * bit is beyond the DMA mask of the chip.
>> +	 */
>> +	if (mem_encrypt_active() && ((flags & AMD_ASIC_MASK) == CHIP_RAVEN)) {
>> +		dev_info(&pdev->dev,
>> +			 "SME is not compatible with RAVEN\n");
>> +		return -ENOTSUPP;
>> +	}
>> +
>>   #ifdef CONFIG_DRM_AMDGPU_SI
>>   	if (!amdgpu_si_support) {
>>   		switch (flags & AMD_ASIC_MASK) {
>> -- 
>> 2.25.4
>>
> Looks good to me, thanks.
>
> Acked-by: Joerg Roedel <jroedel@...e.de>

This is really unfortunate, but I don't see any other solution either.

Reviewed-by: Christian König <christian.koenig@....com>