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Commit a5ddde4a authored by Ian Campbell's avatar Ian Campbell Committed by Ingo Molnar
Browse files

swiotlb: add comment where we handle the overflow of a dma mask on 32 bit 



Impact: cleanup

Signed-off-by: default avatarIan Campbell <ian.campbell@citrix.com>
Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 0016fdee

lib/swiotlb.c

+4 −0
Original line number Diff line number Diff line
@@ -301,6 +301,10 @@ map_single(struct device *hwdev, char *buffer, size_t size, int dir) 
	start_dma_addr = virt_to_bus(io_tlb_start) & mask;



	offset_slots = ALIGN(start_dma_addr, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;



	/*

 	 * Carefully handle integer overflow which can occur when mask == ~0UL.

 	 */

	max_slots = mask + 1

		    ? ALIGN(mask + 1, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT

		    : 1UL << (BITS_PER_LONG - IO_TLB_SHIFT);