[LINUX] swiotlb allocates multiple smaller contiguous DMA regions,

rather than a single big one.
Signed-off-by: Keir Fraser <keir@xensource.com>

linux-2.6-xen-sparse/arch/i386/kernel/swiotlb.c

@@ -47,6 +47,9 @@ EXPORT_SYMBOL(swiotlb);
  */
 #define IO_TLB_SHIFT 11
 
+/* Width of DMA addresses in the IO TLB. 31 bits is an aacraid limitation. */
+#define IO_TLB_DMA_BITS 31
+
 static int swiotlb_force;
 static char *iotlb_virt_start;
 static unsigned long iotlb_nslabs;
@@ -56,10 +59,16 @@ static unsigned long iotlb_nslabs;
  * swiotlb_sync_single_*, to see if the memory was in fact allocated by this
  * API.
  */
-static dma_addr_t iotlb_bus_start, iotlb_bus_end, iotlb_bus_mask;
+static unsigned long iotlb_pfn_start, iotlb_pfn_end;
 
 /* Does the given dma address reside within the swiotlb aperture? */
-#define in_swiotlb_aperture(a) (!(((a) ^ iotlb_bus_start) & iotlb_bus_mask))
+static inline int in_swiotlb_aperture(dma_addr_t dev_addr)
+{
+	unsigned long pfn = mfn_to_local_pfn(dev_addr >> PAGE_SHIFT);
+	return (pfn_valid(pfn)
+		&& (pfn >= iotlb_pfn_start)
+		&& (pfn < iotlb_pfn_end));
+}
 
 /*
  * When the IOMMU overflows we return a fallback buffer. This sets the size.
@@ -125,7 +134,6 @@ void
 swiotlb_init_with_default_size (size_t default_size)
 {
 	unsigned long i, bytes;
-	int rc;
 
 	if (!iotlb_nslabs) {
 		iotlb_nslabs = (default_size >> IO_TLB_SHIFT);
@@ -146,10 +154,13 @@ swiotlb_init_with_default_size (size_t default_size)
 		      "Use dom0_mem Xen boot parameter to reserve\n"
 		      "some DMA memory (e.g., dom0_mem=-128M).\n");
 
-	/* Hardcode 31 address bits for now: aacraid limitation. */
-	rc = xen_create_contiguous_region(
-		(unsigned long)iotlb_virt_start, get_order(bytes), 31);
-	BUG_ON(rc);
+	for (i = 0; i < iotlb_nslabs; i += IO_TLB_SEGSIZE) {
+		int rc = xen_create_contiguous_region(
+			(unsigned long)iotlb_virt_start + (i << IO_TLB_SHIFT),
+			get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT),
+			IO_TLB_DMA_BITS);
+		BUG_ON(rc);
+	}
 
 	/*
 	 * Allocate and initialize the free list array.  This array is used
@@ -167,17 +178,13 @@ swiotlb_init_with_default_size (size_t default_size)
 	 */
 	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);
+	iotlb_pfn_start = __pa(iotlb_virt_start) >> PAGE_SHIFT;
+	iotlb_pfn_end   = iotlb_pfn_start + (bytes >> PAGE_SHIFT);
 
 	printk(KERN_INFO "Software IO TLB enabled: \n"
 	       " Aperture:     %lu megabytes\n"
-	       " Bus range:    0x%016lx - 0x%016lx\n"
 	       " Kernel range: 0x%016lx - 0x%016lx\n",
 	       bytes >> 20,
-	       (unsigned long)iotlb_bus_start,
-	       (unsigned long)iotlb_bus_end,
 	       (unsigned long)iotlb_virt_start,
 	       (unsigned long)iotlb_virt_start + bytes);
 }
@@ -647,7 +654,7 @@ swiotlb_dma_mapping_error(dma_addr_t dma_addr)
 int
 swiotlb_dma_supported (struct device *hwdev, u64 mask)
 {
-	return (mask >= (iotlb_bus_end - 1));
+	return (mask >= ((1UL << IO_TLB_DMA_BITS) - 1));
 }
 
 EXPORT_SYMBOL(swiotlb_init);