diff --git a/arch/x86/xen/pci-swiotlb.c b/arch/x86/xen/pci-swiotlb.c
index ecdbfe2..7fdfccc 100644
--- a/arch/x86/xen/pci-swiotlb.c
+++ b/arch/x86/xen/pci-swiotlb.c
@@ -960,7 +960,7 @@ xen_swiotlb_fixup(void *buf, size_t size, unsigned long nslabs)
 				dma_bits);
 		} while (rc && dma_bits++ < max_dma_bits);
 		if (rc)
-			panic(KERN_ERR "xen_create_contiguous_region failed\n");
+			panic(KERN_ERR "xen_create_contiguous_region failed: rc: %d\n", rc);
 
 		i += slabs;
 	} while(i < nslabs);
@@ -984,7 +984,16 @@ static struct dma_map_ops xen_swiotlb_dma_ops = {
 
 void __init xen_swiotlb_init(void)
 {
-	if (xen_domain()) {
+        int use_swiotlb = 0;
+
+        if (xen_initial_domain())
+                use_swiotlb = 1;
+
+        /* For PV guest, only if iommu=soft is passed in. */
+        if (xen_pv_domain() && !xen_initial_domain() && swiotlb)
+               use_swiotlb = 1;
+ 
+	if (use_swiotlb) {
 		printk(KERN_INFO "PCI-DMA: Using Xen software bounce buffering for IO (Xen-SWIOTLB)\n");
 		xen_swiotlb_init_with_default_size(64 * (1<<20));	/* default to 64MB */
 		dma_ops = &xen_swiotlb_dma_ops;