swiotlb: clear io_tlb_start and io_tlb_end in swiotlb_exit

Otherwise is_swiotlb_buffer will return false positives when
we first initialize a swiotlb buffer, but then free it because
we have an IOMMU available.

Fixes: 601f7fb0b0b1 ("dma-direct: merge swiotlb_dma_ops into the dma_direct code")
Reported-by: Sibren Vasse <sibren@sibrenvasse.nl>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Sibren Vasse <sibren@sibrenvasse.nl>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index d6361776dc5cea40ac830fb6e3940d986dd13841..1fb6fd68b9c7e80c969072642a4064f4e9608008 100644 (file)
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -378,6 +378,8 @@ void __init swiotlb_exit(void)
                memblock_free_late(io_tlb_start,
                                   PAGE_ALIGN(io_tlb_nslabs << IO_TLB_SHIFT));
        }
+       io_tlb_start = 0;
+       io_tlb_end = 0;
        io_tlb_nslabs = 0;
        max_segment = 0;
 }