[Xen-devel] [PATCH] linux: Reduce restrictions on address width for DMA operations

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

Use address width needed by device rather than dma_bits in dma_alloc_coherent().
Probe supported address width in swiotlb initialization.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

Index: sle10-sp1-2006-12-21/arch/i386/kernel/pci-dma-xen.c
===================================================================
--- sle10-sp1-2006-12-21.orig/arch/i386/kernel/pci-dma-xen.c    2007-01-02 
12:36:26.000000000 +0100
+++ sle10-sp1-2006-12-21/arch/i386/kernel/pci-dma-xen.c 2007-01-02 
10:32:16.000000000 +0100
@@ -161,6 +161,8 @@ void *dma_alloc_coherent(struct device *
        struct dma_coherent_mem *mem = dev ? dev->dma_mem : NULL;
        unsigned int order = get_order(size);
        unsigned long vstart;
+       u64 mask;
+
        /* ignore region specifiers */
        gfp &= ~(__GFP_DMA | __GFP_HIGHMEM);
 
@@ -183,9 +185,14 @@ void *dma_alloc_coherent(struct device *
        vstart = __get_free_pages(gfp, order);
        ret = (void *)vstart;
 
+       if (dev != NULL && dev->coherent_dma_mask)
+               mask = dev->coherent_dma_mask;
+       else
+               mask = 0xffffffff;
+
        if (ret != NULL) {
                if (xen_create_contiguous_region(vstart, order,
-                                                dma_bits) != 0) {
+                                                fls64(mask)) != 0) {
                        free_pages(vstart, order);
                        return NULL;
                }
Index: sle10-sp1-2006-12-21/arch/i386/kernel/swiotlb.c
===================================================================
--- sle10-sp1-2006-12-21.orig/arch/i386/kernel/swiotlb.c        2007-01-02 
12:36:26.000000000 +0100
+++ sle10-sp1-2006-12-21/arch/i386/kernel/swiotlb.c     2007-01-02 
12:48:40.000000000 +0100
@@ -47,9 +47,6 @@ EXPORT_SYMBOL(swiotlb);
  */
 #define IO_TLB_SHIFT 11
 
-/* Width of DMA addresses. 30 bits is a b44 limitation. */
-#define DEFAULT_DMA_BITS 30
-
 static int swiotlb_force;
 static char *iotlb_virt_start;
 static unsigned long iotlb_nslabs;
@@ -98,11 +95,12 @@ static struct phys_addr {
  */
 static DEFINE_SPINLOCK(io_tlb_lock);
 
-unsigned int dma_bits = DEFAULT_DMA_BITS;
+static unsigned int dma_bits;
+static unsigned int __initdata max_dma_bits = 32;
 static int __init
 setup_dma_bits(char *str)
 {
-       dma_bits = simple_strtoul(str, NULL, 0);
+       max_dma_bits = simple_strtoul(str, NULL, 0);
        return 0;
 }
 __setup("dma_bits=", setup_dma_bits);
@@ -143,6 +141,7 @@ 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);
@@ -159,16 +158,33 @@ swiotlb_init_with_default_size (size_t d
         */
        iotlb_virt_start = alloc_bootmem_low_pages(bytes);
        if (!iotlb_virt_start)
-               panic("Cannot allocate SWIOTLB buffer!\n"
-                     "Use dom0_mem Xen boot parameter to reserve\n"
-                     "some DMA memory (e.g., dom0_mem=-128M).\n");
+               panic("Cannot allocate SWIOTLB buffer!\n");
 
+       dma_bits = get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT) + PAGE_SHIFT;
        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),
-                       dma_bits);
-               BUG_ON(rc);
+               do {
+                       rc = xen_create_contiguous_region(
+                               (unsigned long)iotlb_virt_start + (i << 
IO_TLB_SHIFT),
+                               get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT),
+                               dma_bits);
+               } while (rc && dma_bits++ < max_dma_bits);
+               if (rc) {
+                       if (i == 0)
+                               panic("No suitable physical memory available 
for SWIOTLB buffer!\n"
+                                     "Use dom0_mem Xen boot parameter to 
reserve\n"
+                                     "some DMA memory (e.g., 
dom0_mem=-128M).\n");
+                       iotlb_nslabs = i;
+                       i <<= IO_TLB_SHIFT;
+                       free_bootmem(__pa(iotlb_virt_start + i), bytes - i);
+                       bytes = i;
+                       for (dma_bits = 0; i > 0; i -= IO_TLB_SEGSIZE << 
IO_TLB_SHIFT) {
+                               unsigned int bits = 
fls64(virt_to_bus(iotlb_virt_start + i - 1));
+
+                               if (bits > dma_bits)
+                                       dma_bits = bits;
+                       }
+                       break;
+               }
        }
 
        /*
@@ -186,17 +202,27 @@ swiotlb_init_with_default_size (size_t d
         * Get the overflow emergency buffer
         */
        io_tlb_overflow_buffer = alloc_bootmem_low(io_tlb_overflow);
+       if (!io_tlb_overflow_buffer)
+               panic("Cannot allocate SWIOTLB overflow buffer!\n");
+
+       do {
+               rc = xen_create_contiguous_region(
+                       (unsigned long)io_tlb_overflow_buffer,
+                       get_order(io_tlb_overflow),
+                       dma_bits);
+       } while (rc && dma_bits++ < max_dma_bits);
+       if (rc)
+               panic("No suitable physical memory available for SWIOTLB 
overflow buffer!\n");
 
        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"
-              " Kernel range: 0x%016lx - 0x%016lx\n"
+              " Kernel range: %p - %p\n"
               " Address size: %u bits\n",
               bytes >> 20,
-              (unsigned long)iotlb_virt_start,
-              (unsigned long)iotlb_virt_start + bytes,
+              iotlb_virt_start, iotlb_virt_start + bytes,
               dma_bits);
 }
 
Index: sle10-sp1-2006-12-21/include/asm-i386/mach-xen/asm/swiotlb.h
===================================================================
--- sle10-sp1-2006-12-21.orig/include/asm-i386/mach-xen/asm/swiotlb.h   
2007-01-02 12:36:26.000000000 +0100
+++ sle10-sp1-2006-12-21/include/asm-i386/mach-xen/asm/swiotlb.h        
2007-01-02 10:28:31.000000000 +0100
@@ -34,8 +34,6 @@ extern void swiotlb_unmap_page(struct de
 extern int swiotlb_dma_supported(struct device *hwdev, u64 mask);
 extern void swiotlb_init(void);
 
-extern unsigned int dma_bits;
-
 #ifdef CONFIG_SWIOTLB
 extern int swiotlb;
 #else


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