Re: [PATCH v10 06/50] x86/sev: Add the host SEV-SNP initialization support

[Borislav Petkov <bp@alien8.de>]

Ontop. Only build-tested.

---
diff --git a/arch/x86/include/asm/iommu.h b/arch/x86/include/asm/iommu.h
index 2fd52b65deac..3be2451e7bc8 100644
--- a/arch/x86/include/asm/iommu.h
+++ b/arch/x86/include/asm/iommu.h
@@ -10,6 +10,7 @@ extern int force_iommu, no_iommu;
 extern int iommu_detected;
 extern int iommu_merge;
 extern int panic_on_overflow;
+extern bool amd_iommu_snp_en;
 
 #ifdef CONFIG_SWIOTLB
 extern bool x86_swiotlb_enable;
diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
index 8b9ed72489e4..9237c327ad6d 100644
--- a/arch/x86/virt/svm/sev.c
+++ b/arch/x86/virt/svm/sev.c
@@ -196,23 +196,15 @@ static __init int __snp_rmptable_init(void)
 
 static int __init snp_rmptable_init(void)
 {
-	int family, model;
-
-	if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+	if (!amd_iommu_snp_en)
 		return 0;
 
-	family = boot_cpu_data.x86;
-	model  = boot_cpu_data.x86_model;
-
 	/*
 	 * RMP table entry format is not architectural and it can vary by processor and
 	 * is defined by the per-processor PPR. Restrict SNP support on the known CPU
 	 * model and family for which the RMP table entry format is currently defined for.
 	 */
-	if (family != 0x19 || model > 0xaf)
-		goto nosnp;
-
-	if (amd_iommu_snp_enable())
+	if (boot_cpu_data.x86 != 0x19 || boot_cpu_data.x86_model > 0xaf)
 		goto nosnp;
 
 	if (__snp_rmptable_init())
@@ -228,12 +220,10 @@ static int __init snp_rmptable_init(void)
 }
 
 /*
- * This must be called after the PCI subsystem. This is because amd_iommu_snp_enable()
- * is called to ensure the IOMMU supports the SEV-SNP feature, which can only be
- * called after subsys_initcall().
+ * This must be called after the IOMMU has been initialized.
  *
  * NOTE: IOMMU is enforced by SNP to ensure that hypervisor cannot program DMA
  * directly into guest private memory. In case of SNP, the IOMMU ensures that
  * the page(s) used for DMA are hypervisor owned.
  */
-fs_initcall(snp_rmptable_init);
+device_initcall(snp_rmptable_init);
diff --git a/drivers/iommu/amd/amd_iommu.h b/drivers/iommu/amd/amd_iommu.h
index e2857109e966..353d68b25fe2 100644
--- a/drivers/iommu/amd/amd_iommu.h
+++ b/drivers/iommu/amd/amd_iommu.h
@@ -148,6 +148,4 @@ struct dev_table_entry *get_dev_table(struct amd_iommu *iommu);
 
 extern u64 amd_iommu_efr;
 extern u64 amd_iommu_efr2;
-
-extern bool amd_iommu_snp_en;
 #endif
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 1c9924de607a..9e72cd8413bb 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -3255,6 +3255,35 @@ static bool __init detect_ivrs(void)
 	return true;
 }
 
+#ifdef CONFIG_KVM_AMD_SEV
+static void iommu_snp_enable(void)
+{
+	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");
+		return;
+	}
+
+	amd_iommu_snp_en = check_feature_on_all_iommus(FEATURE_SNP);
+	if (!amd_iommu_snp_en)
+		return;
+
+	pr_info("SNP enabled\n");
+
+	/* Enforce IOMMU v1 pagetable when SNP is enabled. */
+	if (amd_iommu_pgtable != AMD_IOMMU_V1) {
+		pr_warn("Force to using AMD IOMMU v1 page table due to SNP\n");
+		amd_iommu_pgtable = AMD_IOMMU_V1;
+	}
+}
+#endif
+
 /****************************************************************************
  *
  * AMD IOMMU Initialization State Machine
@@ -3290,6 +3319,7 @@ static int __init state_next(void)
 		break;
 	case IOMMU_ENABLED:
 		register_syscore_ops(&amd_iommu_syscore_ops);
+		iommu_snp_enable();
 		ret = amd_iommu_init_pci();
 		init_state = ret ? IOMMU_INIT_ERROR : IOMMU_PCI_INIT;
 		break;
@@ -3802,40 +3832,4 @@ int amd_iommu_pc_set_reg(struct amd_iommu *iommu, u8 bank, u8 cntr, u8 fxn, u64
 	return iommu_pc_get_set_reg(iommu, bank, cntr, fxn, value, true);
 }
 
-#ifdef CONFIG_KVM_AMD_SEV
-int amd_iommu_snp_enable(void)
-{
-	/*
-	 * 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");
-		return -EINVAL;
-	}
-
-	/*
-	 * Prevent enabling SNP after IOMMU_ENABLED state because this process
-	 * affect how IOMMU driver sets up data structures and configures
-	 * IOMMU hardware.
-	 */
-	if (init_state > IOMMU_ENABLED) {
-		pr_err("SNP: Too late to enable SNP for IOMMU.\n");
-		return -EINVAL;
-	}
-
-	amd_iommu_snp_en = check_feature_on_all_iommus(FEATURE_SNP);
-	if (!amd_iommu_snp_en)
-		return -EINVAL;
-
-	pr_info("SNP enabled\n");
-
-	/* Enforce IOMMU v1 pagetable when SNP is enabled. */
-	if (amd_iommu_pgtable != AMD_IOMMU_V1) {
-		pr_warn("Force to using AMD IOMMU v1 page table due to SNP\n");
-		amd_iommu_pgtable = AMD_IOMMU_V1;
-	}
 
-	return 0;
-}
-#endif

-- 
Regards/Gruss,
    Boris.

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