[PATCH v2 6/6] iommu/amd: Add command-line option to enable different page table

[Vasant Hegde <vasant.hegde@amd.com>]

Enhance amd_iommu command line option to specify v1 or v2 page table.
By default system will boot in V1 page table mode.

Co-developed-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
---
Changes in v2:
  - Removed separate command line option and enhace amd_iommu option
  - Update document

 .../admin-guide/kernel-parameters.txt         |  2 ++
 drivers/iommu/amd/init.c                      | 23 +++++++++++++++----
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index d45e58328ce6..d1919bf4f37a 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -321,6 +321,8 @@
 			force_enable - Force enable the IOMMU on platforms known
 				       to be buggy with IOMMU enabled. Use this
 				       option with care.
+			pgtbl_v1     - Use v1 page table for DMA-API (Default).
+			pgtbl_v2     - Use v2 page table for DMA-API.
 
 	amd_iommu_dump=	[HW,X86-64]
 			Enable AMD IOMMU driver option to dump the ACPI table
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index a2929d8b44f4..673c263fea8d 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -3287,17 +3287,30 @@ static int __init parse_amd_iommu_intr(char *str)
 
 static int __init parse_amd_iommu_options(char *str)
 {
-	for (; *str; ++str) {
+	if (!str)
+		return -EINVAL;
+
+	while (*str) {
 		if (strncmp(str, "fullflush", 9) == 0) {
 			pr_warn("amd_iommu=fullflush deprecated; use iommu.strict=1 instead\n");
 			iommu_set_dma_strict();
-		}
-		if (strncmp(str, "force_enable", 12) == 0)
+		} else if (strncmp(str, "force_enable", 12) == 0) {
 			amd_iommu_force_enable = true;
-		if (strncmp(str, "off", 3) == 0)
+		} else if (strncmp(str, "off", 3) == 0) {
 			amd_iommu_disabled = true;
-		if (strncmp(str, "force_isolation", 15) == 0)
+		} else if (strncmp(str, "force_isolation", 15) == 0) {
 			amd_iommu_force_isolation = true;
+		} else if (strncmp(str, "pgtbl_v1", 8) == 0) {
+			amd_iommu_pgtable = AMD_IOMMU_V1;
+		} else if (strncmp(str, "pgtbl_v2", 8) == 0) {
+			amd_iommu_pgtable = AMD_IOMMU_V2;
+		} else {
+			pr_notice("Unknown option - '%s'\n", str);
+		}
+
+		str += strcspn(str, ",");
+		while (*str == ',')
+			str++;
 	}
 
 	return 1;
-- 
2.31.1