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

I tested your patch, but unfortunately, it doesn't work IA64.
alloc_bootmem_node() requires bigger area than MAX_DMA_ADDRESS.
It is defined as 4GB for ia64. (arch/ia64/mm/init.c)
But this patch require smaller area than 4GB.
So they are exclusive each other.

I'm convinced that a new interface like alloc_bootmem_low32() is
necessary after all. ;-)

Thanks.


> On Tue, Oct 18, 2005 at 01:28:20PM +0900, Yasunori Goto wrote:
> > > > So, just "use NODE(0)" is not enough hack for our machine.
> > > > If "use NODE(0)" is selected, kernel must sort pgdat link and
> > > > node id by memory address. I think that hot add code will be a
> > > > bit messy instead.
> > >
> > > Yasunori-san,
> > > Does this patch work on your boxes instead? (For 2.6.14)
> > > http://marc.theaimsgroup.com/?l=linux-kernel&m=112959469914681&w=2
> >
> > Not yet. But could you change this line at least?
> >
> > +
> > + for_each_node(node) {
> > + io_tlb_start = alloc_bootmem_node(NODE_DATA(node), iotlbsz);
> >
> > for_each_node() loop walks around node_possible_map which includes
> > "offlined" node.
> > Please use for_each_online_node() instead. Then, I'll check it. :-)
>
> Since swiotlb is is allocated even before APs are brought up, I thought,
> if the node containing lowmem32 was not the boot node, it would not be
> online. But on closer look, my assumption was wrong. Here is the patch
> which iterates through online nodes to allocate lowmem32 bootmem for
> swiotlb.
>
> --
>
> Patch to ensure low32 mem allocation for x86_64 swiotlb
>
> Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org>
>
> Index: linux-2.6.14-rc4/arch/ia64/lib/swiotlb.c
> ===================================================================
> --- linux-2.6.14-rc4.orig/arch/ia64/lib/swiotlb.c 2005-10-17 13:27:35.000000000 -0700
> +++ linux-2.6.14-rc4/arch/ia64/lib/swiotlb.c 2005-10-17 16:00:44.000000000 -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 +116,32 @@
> 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) {
> + io_tlb_start = alloc_bootmem_node(NODE_DATA(node), iotlbsz);
> + 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;
> + }
> + }
> +
> +
> if (!io_tlb_start)
> panic("Cannot allocate SWIOTLB buffer");
> io_tlb_end = io_tlb_start + io_tlb_nslabs * (1 << IO_TLB_SHIFT);

--
Yasunori Goto

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