diff -r aeaa3c83f6e5 linux-2.6-xen-sparse/arch/xen/i386/kernel/swiotlb.c
--- a/linux-2.6-xen-sparse/arch/xen/i386/kernel/swiotlb.c	Mon Sep  5 20:05:58 2005
+++ b/linux-2.6-xen-sparse/arch/xen/i386/kernel/swiotlb.c	Tue Sep  6 20:02:44 2005
@@ -51,7 +51,7 @@
  * swiotlb_sync_single_*, to see if the memory was in fact allocated by this
  * API.
  */
-static dma_addr_t iotlb_bus_start, iotlb_bus_mask;
+static dma_addr_t iotlb_bus_start, iotlb_bus_mask, iotlb_bus_end;
 
 /* Does the given dma address reside within the swiotlb aperture? */
 #define in_swiotlb_aperture(a) (!(((a) ^ iotlb_bus_start) & iotlb_bus_mask))
@@ -157,6 +157,7 @@
 	io_tlb_overflow_buffer = alloc_bootmem_low(io_tlb_overflow);
 
 	iotlb_bus_start = virt_to_bus(iotlb_virt_start);
+	iotlb_bus_end   = iotlb_bus_start + bytes;
 	iotlb_bus_mask  = ~(dma_addr_t)(bytes - 1);
 
 	printk(KERN_INFO "Software IO TLB enabled: \n"
@@ -165,7 +166,7 @@
 	       " Kernel range: 0x%016lx - 0x%016lx\n",
 	       bytes >> 20,
 	       (unsigned long)iotlb_bus_start,
-	       (unsigned long)iotlb_bus_start + bytes,
+	       (unsigned long)iotlb_bus_end,
 	       (unsigned long)iotlb_virt_start,
 	       (unsigned long)iotlb_virt_start + bytes);
 }
@@ -191,6 +192,10 @@
 
 	if (swiotlb)
 		swiotlb_init_with_default_size(64 * (1<<20));
+
+	printk(KERN_INFO "swiotlb is %sabled%s\n", 
+	       (swiotlb ? "en" : "dis"), 
+	       (swiotlb_force ? " (forced)" : ""));
 }
 
 static void
@@ -428,8 +433,12 @@
 	/*
 	 * Ensure that the address returned is DMA'ble
 	 */
-	if (address_needs_mapping(hwdev, dev_addr))
-		panic("map_single: bounce buffer is not DMA'ble");
+	if (address_needs_mapping(hwdev, dev_addr)) {
+		printk(KERN_CRIT "swiotlb returning 0x%Lx for ptr %p, but "
+		       "address still needs remapping!\n", 
+		       dev_addr, ptr);
+		BUG_ON(dev_addr);
+	}
 
 	return dev_addr;
 }
@@ -632,7 +641,8 @@
 int
 swiotlb_dma_supported (struct device *hwdev, u64 mask)
 {
-	return (mask >= 0xffffffffUL);
+	/* we can DMA if the mask covers the entire aperture */
+	return ((mask & iotlb_bus_end) == iotlb_bus_end);
 }
 
 EXPORT_SYMBOL(swiotlb_init);
diff -r aeaa3c83f6e5 linux-2.6-xen-sparse/include/asm-xen/asm-x86_64/pci.h
--- a/linux-2.6-xen-sparse/include/asm-xen/asm-x86_64/pci.h	Mon Sep  5 20:05:58 2005
+++ b/linux-2.6-xen-sparse/include/asm-xen/asm-x86_64/pci.h	Tue Sep  6 20:02:44 2005
@@ -76,10 +76,31 @@
 #define pci_unmap_len_set(PTR, LEN_NAME, VAL)		\
 	(((PTR)->LEN_NAME) = (VAL))
 
-#else
-/* No IOMMU */
+#else /* !defined(CONFIG_GART_IOMMU) */
 
-/* On Xen we use SWIOTLB instead of blk-specific bounce buffers. */
+#ifdef CONFIG_SWIOTLB
+
+/* SWIOTLB (bounce buffer) support */
+#define PCI_DMA_BUS_IS_PHYS	(0)
+
+#define pci_dac_dma_supported(pci_dev, mask)    1
+
+#define DECLARE_PCI_UNMAP_ADDR(ADDR_NAME)	\
+	dma_addr_t ADDR_NAME;
+#define DECLARE_PCI_UNMAP_LEN(LEN_NAME)		\
+	__u32 LEN_NAME;
+#define pci_unmap_addr(PTR, ADDR_NAME)			\
+	((PTR)->ADDR_NAME)
+#define pci_unmap_addr_set(PTR, ADDR_NAME, VAL)		\
+	(((PTR)->ADDR_NAME) = (VAL))
+#define pci_unmap_len(PTR, LEN_NAME)			\
+	((PTR)->LEN_NAME)
+#define pci_unmap_len_set(PTR, LEN_NAME, VAL)		\
+	(((PTR)->LEN_NAME) = (VAL))
+
+#else /* !defined(CONFIG_SWIOTLB) */
+
+/* no IOMMU at all */
 #define PCI_DMA_BUS_IS_PHYS	(0)
 
 #define pci_dac_dma_supported(pci_dev, mask)    1
@@ -91,7 +112,8 @@
 #define pci_unmap_len(PTR, LEN_NAME)		(0)
 #define pci_unmap_len_set(PTR, LEN_NAME, VAL)	do { } while (0)
 
-#endif
+#endif /* defined(CONFIG_SWIOTLB) */
+#endif /* defined(CONFIG_GART_IOMMU) */
 
 #include <asm-generic/pci-dma-compat.h>