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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>
This commit is contained in:
FUJITA Tomonori 2008-02-04 22:28:16 -08:00 committed by Linus Torvalds
parent 59fc67dedb
commit 681cc5cd3e
1 changed files with 35 additions and 6 deletions
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41
lib/swiotlb.c
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@ -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);