On Sat, Dec 30, 2023 at 10:19:31AM -0600, Michael Roth wrote:

+static void iommu_snp_enable(void)
+{
+#ifdef CONFIG_KVM_AMD_SEV
+	if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+		return;
+	/*
+	 * The SNP support requires that IOMMU must be enabled, and is
+	 * not configured in the passthrough mode.
+	 */
+	if (no_iommu || iommu_default_passthrough()) {
+		pr_err("SNP: IOMMU is disabled or configured in passthrough mode, SNP cannot be supported.\n");
+		return;
+	}
+
+	amd_iommu_snp_en = check_feature(FEATURE_SNP);
+	if (!amd_iommu_snp_en) {
+		pr_err("SNP: IOMMU SNP feature is not enabled, SNP cannot be supported.\n");
+		return;
+	}
+
+	pr_info("IOMMU SNP support is enabled.\n");
+
+	/* 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;
+	}

Kernel code usually says simple "<bla> enabled" not "<bla> is enabled".
Other than that, LGTM.

---

diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 1ed2ef22a0fb..2f1517acaba0 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c

@@ -3231,17 +3231,17 @@ static void iommu_snp_enable(void)
 	 * not configured in the passthrough mode.
 	 */
 	if (no_iommu || iommu_default_passthrough()) {
-		pr_err("SNP: IOMMU is disabled or configured in passthrough mode, SNP cannot be supported.\n");
+		pr_err("SNP: IOMMU disabled or configured in passthrough mode, SNP cannot be supported.\n");
 		return;
 	}
 
 	amd_iommu_snp_en = check_feature(FEATURE_SNP);
 	if (!amd_iommu_snp_en) {
-		pr_err("SNP: IOMMU SNP feature is not enabled, SNP cannot be supported.\n");
+		pr_err("SNP: IOMMU SNP feature not enabled, SNP cannot be supported.\n");
 		return;
 	}
 
-	pr_info("IOMMU SNP support is enabled.\n");
+	pr_info("IOMMU SNP support enabled.\n");
 
 	/* Enforce IOMMU v1 pagetable when SNP is enabled. */
 	if (amd_iommu_pgtable != AMD_IOMMU_V1) {

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette