From: GuoRui.Yu GuoRui.Yu@linux.alibaba.com
[ Upstream commit 7c3940bf81e5664cdb50c3fedfec8f0a756a34fb ]
In general, if swiotlb is sufficient, the logic of index = wrap_area_index(mem, index + 1) is fine, it will quickly take a slot and release the area->lock; But if swiotlb is insufficient and the device has min_align_mask requirements, such as NVME, we may not be able to satisfy index == wrap and exit the loop properly. In this case, other kernel threads will not be able to acquire the area->lock and release the slot, resulting in a deadlock.
The current implementation of wrap_area_index does not involve a modulo operation, so adjusting the wrap to ensure the loop ends is not trivial. Introduce a new variable to record the number of loops and exit the loop after completing the traversal.
Backtraces: Other CPUs are waiting this core to exit the swiotlb_do_find_slots loop. [10199.924391] RIP: 0010:swiotlb_do_find_slots+0x1fe/0x3e0 [10199.924403] Call Trace: [10199.924404] <TASK> [10199.924405] swiotlb_tbl_map_single+0xec/0x1f0 [10199.924407] swiotlb_map+0x5c/0x260 [10199.924409] ? nvme_pci_setup_prps+0x1ed/0x340 [10199.924411] dma_direct_map_page+0x12e/0x1c0 [10199.924413] nvme_map_data+0x304/0x370 [10199.924415] nvme_prep_rq.part.0+0x31/0x120 [10199.924417] nvme_queue_rq+0x77/0x1f0
... [ 9639.596311] NMI backtrace for cpu 48 [ 9639.596336] Call Trace: [ 9639.596337] [ 9639.596338] _raw_spin_lock_irqsave+0x37/0x40 [ 9639.596341] swiotlb_do_find_slots+0xef/0x3e0 [ 9639.596344] swiotlb_tbl_map_single+0xec/0x1f0 [ 9639.596347] swiotlb_map+0x5c/0x260 [ 9639.596349] dma_direct_map_sg+0x7a/0x280 [ 9639.596352] __dma_map_sg_attrs+0x30/0x70 [ 9639.596355] dma_map_sgtable+0x1d/0x30 [ 9639.596356] nvme_map_data+0xce/0x370
... [ 9639.595665] NMI backtrace for cpu 50 [ 9639.595682] Call Trace: [ 9639.595682] [ 9639.595683] _raw_spin_lock_irqsave+0x37/0x40 [ 9639.595686] swiotlb_release_slots.isra.0+0x86/0x180 [ 9639.595688] dma_direct_unmap_sg+0xcf/0x1a0 [ 9639.595690] nvme_unmap_data.part.0+0x43/0xc0
Fixes: 1f221a0d0dbf ("swiotlb: respect min_align_mask") Signed-off-by: GuoRui.Yu GuoRui.Yu@linux.alibaba.com Signed-off-by: Xiaokang Hu xiaokang.hxk@alibaba-inc.com Signed-off-by: Christoph Hellwig hch@lst.de Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/dma/swiotlb.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index 339a990554e7f..1ecd0d1f7231a 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -617,8 +617,8 @@ static int swiotlb_do_find_slots(struct device *dev, int area_index, unsigned int iotlb_align_mask = dma_get_min_align_mask(dev) & ~(IO_TLB_SIZE - 1); unsigned int nslots = nr_slots(alloc_size), stride; - unsigned int index, wrap, count = 0, i; unsigned int offset = swiotlb_align_offset(dev, orig_addr); + unsigned int index, slots_checked, count = 0, i; unsigned long flags; unsigned int slot_base; unsigned int slot_index; @@ -641,15 +641,16 @@ static int swiotlb_do_find_slots(struct device *dev, int area_index, goto not_found;
slot_base = area_index * mem->area_nslabs; - index = wrap = wrap_area_index(mem, ALIGN(area->index, stride)); + index = wrap_area_index(mem, ALIGN(area->index, stride));
- do { + for (slots_checked = 0; slots_checked < mem->area_nslabs; ) { slot_index = slot_base + index;
if (orig_addr && (slot_addr(tbl_dma_addr, slot_index) & iotlb_align_mask) != (orig_addr & iotlb_align_mask)) { index = wrap_area_index(mem, index + 1); + slots_checked++; continue; }
@@ -665,7 +666,8 @@ static int swiotlb_do_find_slots(struct device *dev, int area_index, goto found; } index = wrap_area_index(mem, index + stride); - } while (index != wrap); + slots_checked += stride; + }
not_found: spin_unlock_irqrestore(&area->lock, flags);