From 57e6840cf79a4af84f44af3f8cfeacd8a14a6c6f Mon Sep 17 00:00:00 2001 From: Chao Gao Date: Fri, 15 Jul 2022 18:45:35 +0800 Subject: 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: Chao Gao Signed-off-by: Christoph Hellwig --- kernel/dma/swiotlb.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index 604f2469ac0e..608923e8dab1 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -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; -- cgit v1.2.3