[RFC PATCH 6/7] iommu/amd: Introduce amd_iommu_pgtable command-line option

[Suravee Suthikulpanit]

To allow specification whether to use v1 or v2 IOMMU pagetable for
DMA remapping when calling kernel DMA-API.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
---
 Documentation/admin-guide/kernel-parameters.txt |  6 ++++++
 drivers/iommu/amd/init.c                        | 15 +++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 04545725f187..466e807369ea 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -319,6 +319,12 @@
 			             This mode requires kvm-amd.avic=1.
 			             (Default when IOMMU HW support is present.)
 
+	amd_iommu_pgtable= [HW,X86-64]
+			Specifies one of the following AMD IOMMU page table to
+			be used for DMA remapping for DMA-API:
+			v1         - Use v1 page table (Default)
+			v2         - Use v2 page table
+
 	amijoy.map=	[HW,JOY] Amiga joystick support
 			Map of devices attached to JOY0DAT and JOY1DAT
 			Format: <a>,<b>
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 9265c1bf1d84..6d5163bfb87e 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -3123,6 +3123,20 @@ static int __init parse_amd_iommu_dump(char *str)
 	return 1;
 }
 
+static int __init parse_amd_iommu_pgtable(char *str)
+{
+	for (; *str; ++str) {
+		if (strncmp(str, "v1", 2) == 0) {
+			amd_iommu_pgtable = AMD_IOMMU_V1;
+			break;
+		} else if (strncmp(str, "v2", 2) == 0) {
+			amd_iommu_pgtable = AMD_IOMMU_V2;
+			break;
+		}
+	}
+	return 1;
+}
+
 static int __init parse_amd_iommu_intr(char *str)
 {
 	for (; *str; ++str) {
@@ -3246,6 +3260,7 @@ static int __init parse_ivrs_acpihid(char *str)
 
 __setup("amd_iommu_dump",	parse_amd_iommu_dump);
 __setup("amd_iommu=",		parse_amd_iommu_options);
+__setup("amd_iommu_pgtable=",	parse_amd_iommu_pgtable);
 __setup("amd_iommu_intr=",	parse_amd_iommu_intr);
 __setup("ivrs_ioapic",		parse_ivrs_ioapic);
 __setup("ivrs_hpet",		parse_ivrs_hpet);
-- 
2.17.1