intel_iommu: Add a placeholder variable for scalable mode stage-1 translation

Add an new element flts in IntelIOMMUState to mark stage-1 translation support
in scalable mode, this element will be exposed as an intel_iommu property
x-flts finally.

For now, it's only a placehholder and used for address width compatibility
check and block host device passthrough until nesting is supported.

Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Clément Mathieu--Drif<clement.mathieu--drif@eviden.com>
Reviewed-by: Yi Liu <yi.l.liu@intel.com>
Message-Id: <20241212083757.605022-4-zhenzhong.duan@intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/i386/intel_iommu.c

@@ -3917,7 +3917,13 @@ static bool vtd_check_hiod(IntelIOMMUState *s, HostIOMMUDevice *hiod,
         return false;
     }
 
-    return true;
+    if (!s->flts) {
+        /* All checks requested by VTD stage-2 translation pass */
+        return true;
+    }
+
+    error_setg(errp, "host device is uncompatible with stage-1 translation");
+    return false;
 }
 
 static bool vtd_dev_set_iommu_device(PCIBus *bus, void *opaque, int devfn,
@@ -4307,14 +4313,21 @@ static bool vtd_decide_config(IntelIOMMUState *s, Error **errp)
         }
     }
 
-    /* Currently only address widths supported are 39 and 48 bits */
-    if ((s->aw_bits != VTD_HOST_AW_39BIT) &&
-        (s->aw_bits != VTD_HOST_AW_48BIT)) {
-        error_setg(errp, "Supported values for aw-bits are: %d, %d",
+    if (!s->flts && s->aw_bits != VTD_HOST_AW_39BIT &&
+        s->aw_bits != VTD_HOST_AW_48BIT) {
+        error_setg(errp, "%s: supported values for aw-bits are: %d, %d",
+                   s->scalable_mode ? "Scalable mode(flts=off)" : "Legacy mode",
                    VTD_HOST_AW_39BIT, VTD_HOST_AW_48BIT);
         return false;
     }
 
+    if (s->flts && s->aw_bits != VTD_HOST_AW_48BIT) {
+        error_setg(errp,
+                   "Scalable mode(flts=on): supported value for aw-bits is: %d",
+                   VTD_HOST_AW_48BIT);
+        return false;
+    }
+
     if (s->scalable_mode && !s->dma_drain) {
         error_setg(errp, "Need to set dma_drain for scalable mode");
         return false;

include/hw/i386/intel_iommu.h

@@ -262,6 +262,7 @@ struct IntelIOMMUState {
 
     bool caching_mode;              /* RO - is cap CM enabled? */
     bool scalable_mode;             /* RO - is Scalable Mode supported? */
+    bool flts;                      /* RO - is stage-1 translation supported? */
     bool snoop_control;             /* RO - is SNP filed supported? */
 
     dma_addr_t root;                /* Current root table pointer */