Commit b650b38b authored by Vasant Hegde's avatar Vasant Hegde Committed by Joerg Roedel
Browse files

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 <ashish.kalra@amd.com>
Cc: Michael Roth <michael.roth@amd.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: default avatarVasant Hegde <vasant.hegde@amd.com>
Reviewed-by: default avatarTom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20240410085702.31869-1-vasant.hegde@amd.com


Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
parent 84b1cec4

drivers/iommu/amd/init.c

+11 −10
Original line number Diff line number Diff line
@@ -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

}