Commit 57e6840c authored by Chao Gao's avatar Chao Gao Committed by Christoph Hellwig
Browse files

swiotlb: ensure a segment doesn't cross the area boundary 



Free slots tracking assumes that slots in a segment can be allocated to
fulfill a request. This implies that slots in a segment should belong to
the same area. Although the possibility of a violation is low, it is better
to explicitly enforce segments won't span multiple areas by adjusting the
number of slabs when configuring areas.

Signed-off-by: default avatarChao Gao <chao.gao@intel.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent 44335487

kernel/dma/swiotlb.c

+10 −1
Original line number Diff line number Diff line
@@ -91,12 +91,21 @@ struct io_tlb_area { 
/*

 * Round up number of slabs to the next power of 2. The last area is going

 * be smaller than the rest if default_nslabs is not power of two.

 * The number of slot in an area should be a multiple of IO_TLB_SEGSIZE,

 * otherwise a segment may span two or more areas. It conflicts with free

 * contiguous slots tracking: free slots are treated contiguous no matter

 * whether they cross an area boundary.

 *

 * Return true if default_nslabs is rounded up.

 */

static bool round_up_default_nslabs(void)

{

	if (!default_nareas || is_power_of_2(default_nslabs))

	if (!default_nareas)

		return false;



	if (default_nslabs < IO_TLB_SEGSIZE * default_nareas)

		default_nslabs = IO_TLB_SEGSIZE * default_nareas;

	else if (is_power_of_2(default_nslabs))

		return false;

	default_nslabs = roundup_pow_of_two(default_nslabs);

	return true;