linux-kernel - [PATCH v3 7/7] iommu/amd: Do not support IOMMUv2 APIs when SNP is enabled

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Date:   Wed, 22 Jun 2022 12:11:31 -0500
From:   Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To:     <linux-kernel@...r.kernel.org>, <iommu@...ts.linux-foundation.org>
CC:     <joro@...tes.org>, <robin.murphy@....com>, <ashish.kalra@....com>,
        <vasant.hegde@....com>, <thomas.lendacky@....com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: [PATCH v3 7/7] iommu/amd: Do not support IOMMUv2 APIs when SNP is enabled

The IOMMUv2 APIs (for supporting shared virtual memory with PASID)
configures the domain with IOMMU v2 page table, and sets DTE[Mode]=0.
This configuration cannot be supported on SNP-enabled system.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
 drivers/iommu/amd/init.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index f5695ccb7c81..4c9b96160a8b 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -3448,7 +3448,12 @@ __setup("ivrs_acpihid",		parse_ivrs_acpihid);
 
 bool amd_iommu_v2_supported(void)
 {
-	return amd_iommu_v2_present;
+	/*
+	 * Since DTE[Mode]=0 is prohibited on SNP-enabled system
+	 * (i.e. EFR[SNPSup]=1), IOMMUv2 page table cannot be used without
+	 * setting up IOMMUv1 page table.
+	 */
+	return amd_iommu_v2_present && !amd_iommu_snp_en;
 }
 EXPORT_SYMBOL(amd_iommu_v2_supported);
 
-- 
2.32.0