iommu sg merging: swiotlb: respect the segment boundary limits

This patch makes swiotlb not allocate a memory area spanning LLD's segment
boundary.

is_span_boundary() judges whether a memory area spans LLD's segment boundary.
If map_single finds such a area, map_single tries to find the next available
memory area.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Greg KH <greg@kroah.com>
Cc: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 35 insertions, 6 deletions

diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index 1a8050ade861..4bb5a11e18a2 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -282,6 +282,15 @@ address_needs_mapping(struct device *hwdev, dma_addr_t addr)
         return (addr & ~mask) != 0;
 }
 
+static inline unsigned int is_span_boundary(unsigned int index,
+                                            unsigned int nslots,
+                                            unsigned long offset_slots,
+                                            unsigned long max_slots)
+{
+        unsigned long offset = (offset_slots + index) & (max_slots - 1);
+        return offset + nslots > max_slots;
+}
+
 /*
  * Allocates bounce buffer and returns its kernel virtual address.
  */
@@ -292,6 +301,16 @@ map_single(struct device *hwdev, char *buffer, size_t size, int dir)
         char *dma_addr;
         unsigned int nslots, stride, index, wrap;
         int i;
+        unsigned long start_dma_addr;
+        unsigned long mask;
+        unsigned long offset_slots;
+        unsigned long max_slots;
+
+        mask = dma_get_seg_boundary(hwdev);
+        start_dma_addr = virt_to_bus(io_tlb_start) & mask;
+
+        offset_slots = ALIGN(start_dma_addr, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
+        max_slots = ALIGN(mask + 1, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
 
         /*
          * For mappings greater than a page, we limit the stride (and
@@ -311,10 +330,17 @@ map_single(struct device *hwdev, char *buffer, size_t size, int dir)
          */
         spin_lock_irqsave(&io_tlb_lock, flags);
         {
-                wrap = index = ALIGN(io_tlb_index, stride);
-
+                index = ALIGN(io_tlb_index, stride);
                 if (index >= io_tlb_nslabs)
-                        wrap = index = 0;
+                        index = 0;
+
+                while (is_span_boundary(index, nslots, offset_slots,
+                                        max_slots)) {
+                        index += stride;
+                        if (index >= io_tlb_nslabs)
+                                index = 0;
+                }
+                wrap = index;
 
                 do {
                         /*
@@ -341,9 +367,12 @@ map_single(struct device *hwdev, char *buffer, size_t size, int dir)
 
                                 goto found;
                         }
-                        index += stride;
-                        if (index >= io_tlb_nslabs)
-                                index = 0;
+                        do {
+                                index += stride;
+                                if (index >= io_tlb_nslabs)
+                                        index = 0;
+                        } while (is_span_boundary(index, nslots, offset_slots,
+                                                  max_slots));
                 } while (index != wrap);
 
                 spin_unlock_irqrestore(&io_tlb_lock, flags);