From b650b38b006053ef96e90b8e3f7e6edc7845cd57 Mon Sep 17 00:00:00 2001 From: Vasant Hegde Date: Wed, 10 Apr 2024 08:57:02 +0000 Subject: iommu/amd: Do not enable SNP when V2 page table is enabled DTE[Mode]=0 is not supported when SNP is enabled in the host. That means to support SNP, IOMMU must be configured with V1 page table (See IOMMU spec [1] for the details). If user passes kernel command line to configure IOMMU domains with v2 page table (amd_iommu=pgtbl_v2) then disable SNP as the user asked by not forcing the page table to v1. [1] https://www.amd.com/content/dam/amd/en/documents/processor-tech-docs/specifications/48882_IOMMU.pdf Cc: Ashish Kalra Cc: Michael Roth Cc: Tom Lendacky Signed-off-by: Vasant Hegde Reviewed-by: Tom Lendacky Link: https://lore.kernel.org/r/20240410085702.31869-1-vasant.hegde@amd.com Signed-off-by: Joerg Roedel --- drivers/iommu/amd/init.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-) diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c index 33228c1c8980f..a714eb08c08b5 100644 --- a/drivers/iommu/amd/init.c +++ b/drivers/iommu/amd/init.c @@ -3232,28 +3232,29 @@ static void iommu_snp_enable(void) return; /* * The SNP support requires that IOMMU must be enabled, and is - * not configured in the passthrough mode. + * configured with V1 page table (DTE[Mode] = 0 is not supported). */ if (no_iommu || iommu_default_passthrough()) { pr_err("SNP: IOMMU disabled or configured in passthrough mode, SNP cannot be supported.\n"); - cc_platform_clear(CC_ATTR_HOST_SEV_SNP); - return; + goto disable_snp; + } + + if (amd_iommu_pgtable != AMD_IOMMU_V1) { + pr_warn("SNP: IOMMU is configured with V2 page table mode, SNP cannot be supported.\n"); + goto disable_snp; } amd_iommu_snp_en = check_feature(FEATURE_SNP); if (!amd_iommu_snp_en) { pr_err("SNP: IOMMU SNP feature not enabled, SNP cannot be supported.\n"); - cc_platform_clear(CC_ATTR_HOST_SEV_SNP); - return; + goto disable_snp; } pr_info("IOMMU SNP support enabled.\n"); + return; - /* Enforce IOMMU v1 pagetable when SNP is enabled. */ - if (amd_iommu_pgtable != AMD_IOMMU_V1) { - pr_warn("Forcing use of AMD IOMMU v1 page table due to SNP.\n"); - amd_iommu_pgtable = AMD_IOMMU_V1; - } +disable_snp: + cc_platform_clear(CC_ATTR_HOST_SEV_SNP); #endif } -- cgit 1.2.3-korg