intel-iommu: Export a flag indicating that the IOMMU is used for iGFX.

We really don't want this to work in the general case; device drivers
*shouldn't* care whether they are behind an IOMMU or not. But the
integrated graphics is a special case, because the IOMMU and the GTT are
all kind of smashed into one and generally horrifically buggy, so it's
reasonable for the graphics driver to want to know when the IOMMU is
active for the graphics hardware.
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/iommu/intel-iommu.c

@@ -404,6 +404,9 @@ static int dmar_forcedac;
 static int intel_iommu_strict;
 static int intel_iommu_superpage = 1;
 
+int intel_iommu_gfx_mapped;
+EXPORT_SYMBOL_GPL(intel_iommu_gfx_mapped);
+
 #define DUMMY_DEVICE_DOMAIN_INFO ((struct device_domain_info *)(-1))
 static DEFINE_SPINLOCK(device_domain_lock);
 static LIST_HEAD(device_domain_list);
@@ -3226,9 +3229,6 @@ static void __init init_no_remapping_devices(void)
 		}
 	}
 
-	if (dmar_map_gfx)
-		return;
-
 	for_each_drhd_unit(drhd) {
 		int i;
 		if (drhd->ignored || drhd->include_all)
@@ -3236,18 +3236,23 @@ static void __init init_no_remapping_devices(void)
 
 		for (i = 0; i < drhd->devices_cnt; i++)
 			if (drhd->devices[i] &&
-				!IS_GFX_DEVICE(drhd->devices[i]))
+			    !IS_GFX_DEVICE(drhd->devices[i]))
 				break;
 
 		if (i < drhd->devices_cnt)
 			continue;
 
-		/* bypass IOMMU if it is just for gfx devices */
-		drhd->ignored = 1;
-		for (i = 0; i < drhd->devices_cnt; i++) {
-			if (!drhd->devices[i])
-				continue;
-			drhd->devices[i]->dev.archdata.iommu = DUMMY_DEVICE_DOMAIN_INFO;
+		/* This IOMMU has *only* gfx devices. Either bypass it or
+		   set the gfx_mapped flag, as appropriate */
+		if (dmar_map_gfx) {
+			intel_iommu_gfx_mapped = 1;
+		} else {
+			drhd->ignored = 1;
+			for (i = 0; i < drhd->devices_cnt; i++) {
+				if (!drhd->devices[i])
+					continue;
+				drhd->devices[i]->dev.archdata.iommu = DUMMY_DEVICE_DOMAIN_INFO;
+			}
 		}
 	}
 }