linux-kernel - [PATCH 1/2] iommu/amd: Do not force direct mapping when SME is active

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Date:   Mon, 24 Aug 2020 12:54:14 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     iommu@...ts.linux-foundation.org
Cc:     Joerg Roedel <joro@...tes.org>, jroedel@...e.de,
        Tom Lendacky <thomas.lendacky@....com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        Alexander.Deucher@....com, linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] iommu/amd: Do not force direct mapping when SME is active

From: Joerg Roedel <jroedel@...e.de>

Do not force devices supporting IOMMUv2 to be direct mapped when memory
encryption is active. This might cause them to be unusable because their
DMA mask does not include the encryption bit.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 drivers/iommu/amd/iommu.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index ba9f3dbc5b94..77e4268e41cf 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -2659,7 +2659,12 @@ static int amd_iommu_def_domain_type(struct device *dev)
 	if (!dev_data)
 		return 0;
 
-	if (dev_data->iommu_v2)
+	/*
+	 * Do not identity map IOMMUv2 capable devices when memory encryption is
+	 * active, because some of those devices (AMD GPUs) don't have the
+	 * encryption bit in their DMA-mask and require remapping.
+	 */
+	if (!mem_encrypt_active() && dev_data->iommu_v2)
 		return IOMMU_DOMAIN_IDENTITY;
 
 	return 0;
-- 
2.28.0