From: Yi Liu <yi.l.liu@intel.com>

Intel VT-d 3.0 introduces scalable mode, and it has a bunch of capabilities
related to scalable mode translation, thus there are multiple combinations.
While this vIOMMU implementation wants to simplify it for user by providing
typical combinations. User could config it by "x-scalable-mode" option. The
usage is as below:

"-device intel-iommu,x-scalable-mode=["legacy"|"modern"|"off"]"

 - "legacy": gives support for stage-2 page table
 - "modern": gives support for stage-1 page table
 - "off": no scalable mode support
 -  if not configured, means no scalable mode support, if not proper
    configured, will throw error

Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Signed-off-by: Yi Sun <yi.y.sun@linux.intel.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
---
 include/hw/i386/intel_iommu.h |  1 +
 hw/i386/intel_iommu.c         | 24 +++++++++++++++++++++++-
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/include/hw/i386/intel_iommu.h b/include/hw/i386/intel_iommu.h
index b0d5b5a5be..dd032b1081 100644
--- a/include/hw/i386/intel_iommu.h
+++ b/include/hw/i386/intel_iommu.h
@@ -264,6 +264,7 @@ struct IntelIOMMUState {
 
     bool caching_mode;              /* RO - is cap CM enabled? */
     bool scalable_mode;             /* RO - is Scalable Mode supported? */
+    char *scalable_mode_str;        /* RO - admin's Scalable Mode config */
     bool scalable_modern;           /* RO - is modern SM supported? */
     bool snoop_control;             /* RO - is SNP filed supported? */
 
diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index a4c241ea96..1bd91fcf4c 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -3750,7 +3750,7 @@ static Property vtd_properties[] = {
     DEFINE_PROP_UINT8("aw-bits", IntelIOMMUState, aw_bits,
                       0xff),
     DEFINE_PROP_BOOL("caching-mode", IntelIOMMUState, caching_mode, FALSE),
-    DEFINE_PROP_BOOL("x-scalable-mode", IntelIOMMUState, scalable_mode, FALSE),
+    DEFINE_PROP_STRING("x-scalable-mode", IntelIOMMUState, scalable_mode_str),
     DEFINE_PROP_BOOL("snoop-control", IntelIOMMUState, snoop_control, false),
     DEFINE_PROP_BOOL("x-pasid-mode", IntelIOMMUState, pasid, false),
     DEFINE_PROP_BOOL("dma-drain", IntelIOMMUState, dma_drain, true),
@@ -4663,6 +4663,28 @@ static bool vtd_decide_config(IntelIOMMUState *s, Error **errp)
         }
     }
 
+    if (s->scalable_mode_str &&
+        (strcmp(s->scalable_mode_str, "off") &&
+         strcmp(s->scalable_mode_str, "modern") &&
+         strcmp(s->scalable_mode_str, "legacy"))) {
+        error_setg(errp, "Invalid x-scalable-mode config,"
+                         "Please use \"modern\", \"legacy\" or \"off\"");
+        return false;
+    }
+
+    if (s->scalable_mode_str &&
+        !strcmp(s->scalable_mode_str, "legacy")) {
+        s->scalable_mode = true;
+        s->scalable_modern = false;
+    } else if (s->scalable_mode_str &&
+        !strcmp(s->scalable_mode_str, "modern")) {
+        s->scalable_mode = true;
+        s->scalable_modern = true;
+    } else {
+        s->scalable_mode = false;
+        s->scalable_modern = false;
+    }
+
     if (s->aw_bits == 0xff) {
         if (s->scalable_modern) {
             s->aw_bits = VTD_HOST_AW_48BIT;
-- 
2.34.1