[PATCH 14/19] swiotlb-xen: Add 'xen_swiotlb_init' function.

[Konrad Rzeszutek Wilk]

We utilize the alloc_bootmem to allocate any memory (even
past the 4GB) and then follow it with a xen kernel
to replace the memory pointed by the virtual address with memory
that is under the 4GB mark.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 lib/swiotlb-xen.c |   68 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 67 insertions(+), 1 deletions(-)

diff --git a/lib/swiotlb-xen.c b/lib/swiotlb-xen.c
index e0f944e..3c5bfde 100644
--- a/lib/swiotlb-xen.c
+++ b/lib/swiotlb-xen.c
@@ -33,10 +33,10 @@
  *
  */
 
+#include <linux/bootmem.h>
 #include <linux/dma-mapping.h>
 #include <xen/page.h>
 #include <xen/xen-ops.h>
-
 /*
  * Used to do a quick range check in swiotlb_tbl_unmap_single and
  * swiotlb_tbl_sync_single_*, to see if the memory was in fact allocated by this
@@ -44,6 +44,7 @@
  */
 
 static char *xen_io_tlb_start, *xen_io_tlb_end;
+static unsigned long xen_io_tlb_nslabs;
 
 /* Temporary scaffolding. Will be removed later. */
 void
@@ -124,6 +125,70 @@ xen_map_single(struct device *hwdev, phys_addr_t phys, size_t size,
 	return swiotlb_tbl_map_single(hwdev, start_dma_addr, phys, size, dir);
 }
 
+static int max_dma_bits = 32;
+
+static int
+xen_swiotlb_fixup(void *buf, size_t size, unsigned long nslabs)
+{
+	int i, rc;
+	int dma_bits;
+
+	dma_bits = get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT) + PAGE_SHIFT;
+
+	i = 0;
+	do {
+		int slabs = min(nslabs - i, (unsigned long)IO_TLB_SEGSIZE);
+
+		do {
+			rc = xen_create_contiguous_region(
+				(unsigned long)buf + (i << IO_TLB_SHIFT),
+				get_order(slabs << IO_TLB_SHIFT),
+				dma_bits);
+		} while (rc && dma_bits++ < max_dma_bits);
+		if (rc)
+			return rc;
+
+		i += slabs;
+	} while (i < nslabs);
+	return 0;
+}
+
+void __init xen_swiotlb_init(int verbose)
+{
+	unsigned long bytes;
+	int rc;
+
+	xen_io_tlb_nslabs = (64 * 1024 * 1024 >> IO_TLB_SHIFT);
+	xen_io_tlb_nslabs = ALIGN(xen_io_tlb_nslabs, IO_TLB_SEGSIZE);
+
+	bytes = xen_io_tlb_nslabs << IO_TLB_SHIFT;
+
+	/*
+	 * Get IO TLB memory from any location.
+	 */
+	xen_io_tlb_start = alloc_bootmem(bytes);
+	if (!xen_io_tlb_start)
+		panic("Cannot allocate SWIOTLB buffer");
+
+	xen_io_tlb_end = xen_io_tlb_start + bytes;
+	/*
+	 * And replace that memory with pages under 4GB.
+	 */
+	rc = xen_swiotlb_fixup(xen_io_tlb_start,
+			       bytes,
+			       xen_io_tlb_nslabs);
+	if (rc)
+		goto error;
+
+	swiotlb_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs, verbose);
+
+	return;
+error:
+	panic("DMA(%d): Failed to exchange pages allocated for DMA with Xen! "\
+	      "We either don't have the permission or you do not have enough"\
+	      "free memory under 4GB!\n", rc);
+}
+
 void *
 xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
 			   dma_addr_t *dma_handle, gfp_t flags)
@@ -177,6 +242,7 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
 }
 EXPORT_SYMBOL_GPL(xen_swiotlb_free_coherent);
 
+
 /*
  * Map a single buffer of the indicated size for DMA in streaming mode.  The
  * physical address to use is returned.
-- 
1.7.0.1

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