[PATCH 5/8] swiotlb: refactor swiotlb_tbl_map_single

Christoph Hellwig
2021-02-04T19:31:04Z

Split out a bunch of a self-contained helpers to make the function easier
to follow.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
kernel/dma/swiotlb.c | 177 +++++++++++++++++++++----------------------
1 file changed, 87 insertions(+), 90 deletions(-)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 79d5b236f25f10..e78615e3be2906 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -468,134 +468,131 @@ static void swiotlb_bounce(phys_addr_t orig_addr, phys_addr_t tlb_addr,
}
}

-phys_addr_t swiotlb_tbl_map_single(struct device *hwdev, phys_addr_t orig_addr,
- size_t mapping_size, size_t alloc_size,
- enum dma_data_direction dir, unsigned long attrs)
+/*
+ * Carefully handle integer overflow which can occur when boundary_mask == ~0UL.
+ */
+static inline unsigned long get_max_slots(unsigned long boundary_mask)
{
- dma_addr_t tbl_dma_addr = phys_to_dma_unencrypted(hwdev, io_tlb_start);
- unsigned long flags;
- phys_addr_t tlb_addr;
- unsigned int nslots, stride, index, wrap;
- int i;
- unsigned long mask;
- unsigned long offset_slots;
- unsigned long max_slots;
- unsigned long tmp_io_tlb_used;
-
- if (no_iotlb_memory)
- panic("Can not allocate SWIOTLB buffer earlier and can't now provide you with the DMA bounce buffer");
-
- if (mem_encrypt_active())
- pr_warn_once("Memory encryption is active and system is using DMA bounce buffers\n");
-
- if (mapping_size > alloc_size) {
- dev_warn_once(hwdev, "Invalid sizes (mapping: %zd bytes, alloc: %zd bytes)",
- mapping_size, alloc_size);
- return (phys_addr_t)DMA_MAPPING_ERROR;
- }
-
- mask = dma_get_seg_boundary(hwdev);
+ if (boundary_mask + 1 == ~0UL)
+ return 1UL << (BITS_PER_LONG - IO_TLB_SHIFT);
+ return nr_slots(boundary_mask + 1);
+}

- tbl_dma_addr &= mask;
+static unsigned int wrap_index(unsigned int index)
+{
+ if (index >= io_tlb_nslabs)
+ return 0;
+ return index;
+}

- offset_slots = nr_slots(tbl_dma_addr);
+/*
+ * Find a suitable number of IO TLB entries size that will fit this request and
+ * allocate a buffer from that IO TLB pool.
+ */
+static int find_slots(struct device *dev, size_t alloc_size,
+ dma_addr_t tbl_dma_addr)
+{
+ unsigned int max_slots = get_max_slots(dma_get_seg_boundary(dev));
+ unsigned int nslots = nr_slots(alloc_size), stride = 1;
+ unsigned int index, wrap, count = 0, i;
+ unsigned long flags;

- /*
- * Carefully handle integer overflow which can occur when mask == ~0UL.
- */
- max_slots = mask + 1
- ? nr_slots(mask + 1)
- : 1UL << (BITS_PER_LONG - IO_TLB_SHIFT);
+ BUG_ON(!nslots);

/*
* For mappings greater than or equal to a page, we limit the stride
* (and hence alignment) to a page size.
*/
- nslots = nr_slots(alloc_size);
if (alloc_size >= PAGE_SIZE)
- stride = (1 << (PAGE_SHIFT - IO_TLB_SHIFT));
- else
- stride = 1;
-
- BUG_ON(!nslots);
+ stride <<= (PAGE_SHIFT - IO_TLB_SHIFT);

- /*
- * Find suitable number of IO TLB entries size that will fit this
- * request and allocate a buffer from that IO TLB pool.
- */
spin_lock_irqsave(&io_tlb_lock, flags);
-
if (unlikely(nslots > io_tlb_nslabs - io_tlb_used))
goto not_found;

- index = ALIGN(io_tlb_index, stride);
- if (index >= io_tlb_nslabs)
- index = 0;
- wrap = index;
-
+ index = wrap = wrap_index(ALIGN(io_tlb_index, stride));
do {
- while (iommu_is_span_boundary(index, nslots, offset_slots,
- max_slots)) {
- index += stride;
- if (index >= io_tlb_nslabs)
- index = 0;
- if (index == wrap)
- goto not_found;
- }
-
/*
* If we find a slot that indicates we have 'nslots' number of
* contiguous buffers, we allocate the buffers from that slot
* and mark the entries as '0' indicating unavailable.
*/
- if (io_tlb_list[index] >= nslots) {
- int count = 0;
-
- for (i = index; i < (int) (index + nslots); i++)
- io_tlb_list[i] = 0;
- for (i = index - 1;
- io_tlb_offset(i) != IO_TLB_SEGSIZE - 1 &&
- io_tlb_list[i]; i--)
- io_tlb_list[i] = ++count;
- tlb_addr = io_tlb_start + (index << IO_TLB_SHIFT);
-
- /*
- * Update the indices to avoid searching in the next
- * round.
- */
- io_tlb_index = ((index + nslots) < io_tlb_nslabs
- ? (index + nslots) : 0);
-
- goto found;
+ if (!iommu_is_span_boundary(index, nslots,
+ nr_slots(tbl_dma_addr),
+ max_slots)) {
+ if (io_tlb_list[index] >= nslots)
+ goto found;
}
- index += stride;
- if (index >= io_tlb_nslabs)
- index = 0;
+ index = wrap_index(index + stride);
} while (index != wrap);

not_found:
- tmp_io_tlb_used = io_tlb_used;
-
spin_unlock_irqrestore(&io_tlb_lock, flags);
- if (!(attrs & DMA_ATTR_NO_WARN) && printk_ratelimit())
- dev_warn(hwdev, "swiotlb buffer is full (sz: %zd bytes), total %lu (slots), used %lu (slots)\n",
- alloc_size, io_tlb_nslabs, tmp_io_tlb_used);
- return (phys_addr_t)DMA_MAPPING_ERROR;
+ return -1;
+
found:
+ for (i = index; i < index + nslots; i++)
+ io_tlb_list[i] = 0;
+ for (i = index - 1;
+ io_tlb_offset(i) != IO_TLB_SEGSIZE - 1 &&
+ io_tlb_list[i]; i--)
+ io_tlb_list[i] = ++count;
+
+ /*
+ * Update the indices to avoid searching in the next round.
+ */
+ if (index + nslots < io_tlb_nslabs)
+ io_tlb_index = index + nslots;
+ else
+ io_tlb_index = 0;
io_tlb_used += nslots;
+
spin_unlock_irqrestore(&io_tlb_lock, flags);
+ return index;
+}
+
+phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr,
+ size_t mapping_size, size_t alloc_size,
+ enum dma_data_direction dir, unsigned long attrs)
+{
+ dma_addr_t tbl_dma_addr = phys_to_dma_unencrypted(dev, io_tlb_start) &
+ dma_get_seg_boundary(dev);
+ unsigned int index, i;
+ phys_addr_t tlb_addr;
+
+ if (no_iotlb_memory)
+ panic("Can not allocate SWIOTLB buffer earlier and can't now provide you with the DMA bounce buffer");
+
+ if (mem_encrypt_active())
+ pr_warn_once("Memory encryption is active and system is using DMA bounce buffers\n");
+
+ if (mapping_size > alloc_size) {
+ dev_warn_once(dev, "Invalid sizes (mapping: %zd bytes, alloc: %zd bytes)",
+ mapping_size, alloc_size);
+ return (phys_addr_t)DMA_MAPPING_ERROR;
+ }
+
+ index = find_slots(dev, alloc_size, tbl_dma_addr);
+ if (index == -1) {
+ if (!(attrs & DMA_ATTR_NO_WARN))
+ dev_warn_ratelimited(dev,
+ "swiotlb buffer is full (sz: %zd bytes), total %lu (slots), used %lu (slots)\n",
+ alloc_size, io_tlb_nslabs, io_tlb_used);
+ return (phys_addr_t)DMA_MAPPING_ERROR;
+ }

/*
* Save away the mapping from the original address to the DMA address.
* This is needed when we sync the memory. Then we sync the buffer if
* needed.
*/
- for (i = 0; i < nslots; i++)
- io_tlb_orig_addr[index+i] = orig_addr + (i << IO_TLB_SHIFT);
+ for (i = 0; i < nr_slots(alloc_size); i++)
+ io_tlb_orig_addr[index + i] = orig_addr + (i << IO_TLB_SHIFT);
+
+ tlb_addr = io_tlb_start + (index << IO_TLB_SHIFT);
if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
(dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL))
swiotlb_bounce(orig_addr, tlb_addr, mapping_size, DMA_TO_DEVICE);
-
return tlb_addr;
}

--
2.29.2