Description of problem: 机密VM需要使用swiotlb以进行IO相关操作，由于NVME要求min_align_mask，会使得如下代码的while循环无法退出. static int swiotlb_do_find_slots(struct device *dev, int area_index, phys_addr_t orig_addr, size_t alloc_size, unsigned int alloc_align_mask) { ... do { 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); continue; } /* * If we find a slot that indicates we have 'nslots' number of * contiguous buffers, we allocate the buffers from that slot * and mark the entries as '0' indicating unavailable. */ if (!iommu_is_span_boundary(slot_index, nslots, nr_slots(tbl_dma_addr), max_slots)) { if (mem->slots[slot_index].list >= nslots) goto found; } index = wrap_area_index(mem, index + stride); } while (index != wrap); 一般情况下，如果swiotlb充足，index = wrap_area_index(mem, index + 1)的逻辑是没问题的，它会很快拿走一个tlb_cache然后释放锁； 但是如果非常不幸，它没有找到的话，它就会一直在这个loop里，直至找到才能exit，也就是说它是没有其他的退出路径的； 但是问题是，它一直在loop里会一直持有锁，所以别人是没法归还的，所以形成了死锁。 Version-Release number of selected component (if applicable): How reproducible: 机密计算环境下（TDX/SEV），进行IO压力测试 mkfs.xfs /dev/nvme1n1 Actual results: deadlock Expected results: Additional info: Backtraces: [10199.924391] RIP: 0010:swiotlb_do_find_slots+0x1fe/0x3e0 [10199.924403] Call Trace: [10199.924404] [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 [10199.924420] blk_mq_dispatch_rq_list+0x17e/0x670 [10199.924422] __blk_mq_sched_dispatch_requests+0x129/0x140 [10199.924424] blk_mq_sched_dispatch_requests+0x34/0x60 [10199.924426] __blk_mq_run_hw_queue+0x91/0xb0 [10199.924428] process_one_work+0x1df/0x3b0 [10199.924430] worker_thread+0x49/0x2e0 [10199.924432] ? rescuer_thread+0x390/0x390 [10199.924433] kthread+0xe5/0x110 [10199.924435] ? kthread_complete_and_exit+0x20/0x20 [10199.924436] ret_from_fork+0x1f/0x30 [10199.924439]
merged: https://gitee.com/anolis/cloud-kernel/pulls/1191