Re: [discuss] Re: x86_64: 2.6.14-rc4 swiotlb broken

On Tue, Oct 18, 2005 at 04:37:03PM -0600, Alex Williamson wrote:
> On Tue, 2005-10-18 at 16:04 -0600, Alex Williamson wrote:
> 
>    Nope, it breaks with a current git-2.6.14.  Here's what my extra
> printk says:
> 
> Node 0: 0xe000074104e67200
> Node 1: 0xe000082080722000
> Node 2: 0xe000000101532000
> Placing software IO TLB between 0x74108e68000 - 0x7410ce68000
> 

Hope the following works.   Using __alloc_bootmem_node now with a hard coded
goal to avoid 16MB DMA zone.  It is ugly :( and hope it works this time
<fingers crossed>. 

--

Patch to ensure low32 mem allocation for x86_64 swiotlb

Signed-off-by: Ravikiran Thirumalai <kiran@xxxxxxxxxxxx>

Index: linux-2.6.14-rc4/arch/ia64/lib/swiotlb.c
===================================================================
--- linux-2.6.14-rc4.orig/arch/ia64/lib/swiotlb.c       2005-10-18 
14:14:12.000000000 -0700
+++ linux-2.6.14-rc4/arch/ia64/lib/swiotlb.c    2005-10-18 16:09:51.000000000 
-0700
@@ -106,6 +106,8 @@
 __setup("swiotlb=", setup_io_tlb_npages);
 /* make io_tlb_overflow tunable too? */
 
+#define IS_LOWPAGES(paddr, size) ((paddr < 0xffffffff) && ((paddr+size) < 
0xffffffff))
+
 /*
  * Statically reserve bounce buffer space and initialize bounce buffer data
  * structures for the software IO TLB used to implement the PCI DMA API.
@@ -114,17 +116,46 @@
 swiotlb_init_with_default_size (size_t default_size)
 {
        unsigned long i;
+       unsigned long iotlbsz;
+       int node;
 
        if (!io_tlb_nslabs) {
                io_tlb_nslabs = (default_size >> IO_TLB_SHIFT);
                io_tlb_nslabs = ALIGN(io_tlb_nslabs, IO_TLB_SEGSIZE);
        }
 
+       iotlbsz = io_tlb_nslabs * (1 << IO_TLB_SHIFT);  
+
        /*
-        * Get IO TLB memory from the low pages
+        * Get IO TLB memory from the 0-4G range
         */
-       io_tlb_start = alloc_bootmem_low_pages(io_tlb_nslabs *
-                                              (1 << IO_TLB_SHIFT));
+       
+       for_each_online_node(node) {
+               /* Ugly, hate it.  To be gone post 2.6.14 */
+               io_tlb_start = __alloc_bootmem_node(NODE_DATA(node), 
+                                                   iotlbsz, PAGE_SIZE, 
+                                                   0x1000000);
+               if (io_tlb_start) {
+                       if (IS_LOWPAGES(virt_to_phys(io_tlb_start), iotlbsz))
+                               break;
+                       free_bootmem_node(NODE_DATA(node), 
+                                         virt_to_phys(io_tlb_start), iotlbsz);
+                       io_tlb_start = NULL;
+               }
+       }
+
+       /* 
+        * FIXME: This should go away when the bootmem allocator is fixed to
+        * guarantee lowmem32 allocations somehow, and the swiotlb mess is 
+        * cleaned.  The alloc_bootmem_low_pages fall back is to ensure 
+         * boxes like amd64  which donot use swiotlb but still have 
+        * swiotlb compiled in, falls back to the 2.6.13 behaviour instead
+        * of panicking, when proper low32 pages are not available
+        */
+       if (!io_tlb_start)
+               io_tlb_start = alloc_bootmem_low_pages(io_tlb_nslabs *
+                                                       (1 << IO_TLB_SHIFT));
+
        if (!io_tlb_start)
                panic("Cannot allocate SWIOTLB buffer");
        io_tlb_end = io_tlb_start + io_tlb_nslabs * (1 << IO_TLB_SHIFT);