From: Fenghua Yu fenghua.yu@intel.com
[ Upstream commit 6ef0505158f7ca1b32763a3b038b5d11296b642b ]
pasid_mutex and dev->iommu->param->lock are held while unbinding mm is flushing IO page fault workqueue and waiting for all page fault works to finish. But an in-flight page fault work also need to hold the two locks while unbinding mm are holding them and waiting for the work to finish. This may cause an ABBA deadlock issue as shown below:
idxd 0000:00:0a.0: unbind PASID 2 ====================================================== WARNING: possible circular locking dependency detected 5.14.0-rc7+ #549 Not tainted [ 186.615245] ---------- dsa_test/898 is trying to acquire lock: ffff888100d854e8 (¶m->lock){+.+.}-{3:3}, at: iopf_queue_flush_dev+0x29/0x60 but task is already holding lock: ffffffff82b2f7c8 (pasid_mutex){+.+.}-{3:3}, at: intel_svm_unbind+0x34/0x1e0 which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (pasid_mutex){+.+.}-{3:3}: __mutex_lock+0x75/0x730 mutex_lock_nested+0x1b/0x20 intel_svm_page_response+0x8e/0x260 iommu_page_response+0x122/0x200 iopf_handle_group+0x1c2/0x240 process_one_work+0x2a5/0x5a0 worker_thread+0x55/0x400 kthread+0x13b/0x160 ret_from_fork+0x22/0x30
-> #1 (¶m->fault_param->lock){+.+.}-{3:3}: __mutex_lock+0x75/0x730 mutex_lock_nested+0x1b/0x20 iommu_report_device_fault+0xc2/0x170 prq_event_thread+0x28a/0x580 irq_thread_fn+0x28/0x60 irq_thread+0xcf/0x180 kthread+0x13b/0x160 ret_from_fork+0x22/0x30
-> #0 (¶m->lock){+.+.}-{3:3}: __lock_acquire+0x1134/0x1d60 lock_acquire+0xc6/0x2e0 __mutex_lock+0x75/0x730 mutex_lock_nested+0x1b/0x20 iopf_queue_flush_dev+0x29/0x60 intel_svm_drain_prq+0x127/0x210 intel_svm_unbind+0xc5/0x1e0 iommu_sva_unbind_device+0x62/0x80 idxd_cdev_release+0x15a/0x200 [idxd] __fput+0x9c/0x250 ____fput+0xe/0x10 task_work_run+0x64/0xa0 exit_to_user_mode_prepare+0x227/0x230 syscall_exit_to_user_mode+0x2c/0x60 do_syscall_64+0x48/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae
other info that might help us debug this:
Chain exists of: ¶m->lock --> ¶m->fault_param->lock --> pasid_mutex
Possible unsafe locking scenario:
CPU0 CPU1 ---- ---- lock(pasid_mutex); lock(¶m->fault_param->lock); lock(pasid_mutex); lock(¶m->lock);
*** DEADLOCK ***
2 locks held by dsa_test/898: #0: ffff888100cc1cc0 (&group->mutex){+.+.}-{3:3}, at: iommu_sva_unbind_device+0x53/0x80 #1: ffffffff82b2f7c8 (pasid_mutex){+.+.}-{3:3}, at: intel_svm_unbind+0x34/0x1e0
stack backtrace: CPU: 2 PID: 898 Comm: dsa_test Not tainted 5.14.0-rc7+ #549 Hardware name: Intel Corporation Kabylake Client platform/KBL S DDR4 UD IMM CRB, BIOS KBLSE2R1.R00.X050.P01.1608011715 08/01/2016 Call Trace: dump_stack_lvl+0x5b/0x74 dump_stack+0x10/0x12 print_circular_bug.cold+0x13d/0x142 check_noncircular+0xf1/0x110 __lock_acquire+0x1134/0x1d60 lock_acquire+0xc6/0x2e0 ? iopf_queue_flush_dev+0x29/0x60 ? pci_mmcfg_read+0xde/0x240 __mutex_lock+0x75/0x730 ? iopf_queue_flush_dev+0x29/0x60 ? pci_mmcfg_read+0xfd/0x240 ? iopf_queue_flush_dev+0x29/0x60 mutex_lock_nested+0x1b/0x20 iopf_queue_flush_dev+0x29/0x60 intel_svm_drain_prq+0x127/0x210 ? intel_pasid_tear_down_entry+0x22e/0x240 intel_svm_unbind+0xc5/0x1e0 iommu_sva_unbind_device+0x62/0x80 idxd_cdev_release+0x15a/0x200
pasid_mutex protects pasid and svm data mapping data. It's unnecessary to hold pasid_mutex while flushing the workqueue. To fix the deadlock issue, unlock pasid_pasid during flushing the workqueue to allow the works to be handled.
Fixes: d5b9e4bfe0d8 ("iommu/vt-d: Report prq to io-pgfault framework") Reported-and-tested-by: Dave Jiang dave.jiang@intel.com Signed-off-by: Fenghua Yu fenghua.yu@intel.com Link: https://lore.kernel.org/r/20210826215918.4073446-1-fenghua.yu@intel.com Signed-off-by: Lu Baolu baolu.lu@linux.intel.com Link: https://lore.kernel.org/r/20210828070622.2437559-3-baolu.lu@linux.intel.com [joro: Removed timing information from kernel log messages] Signed-off-by: Joerg Roedel jroedel@suse.de Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/iommu/intel/svm.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)
diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c index ceeca633a5f9..d575082567ca 100644 --- a/drivers/iommu/intel/svm.c +++ b/drivers/iommu/intel/svm.c @@ -793,7 +793,19 @@ prq_retry: goto prq_retry; }
+ /* + * A work in IO page fault workqueue may try to lock pasid_mutex now. + * Holding pasid_mutex while waiting in iopf_queue_flush_dev() for + * all works in the workqueue to finish may cause deadlock. + * + * It's unnecessary to hold pasid_mutex in iopf_queue_flush_dev(). + * Unlock it to allow the works to be handled while waiting for + * them to finish. + */ + lockdep_assert_held(&pasid_mutex); + mutex_unlock(&pasid_mutex); iopf_queue_flush_dev(dev); + mutex_lock(&pasid_mutex);
/* * Perform steps described in VT-d spec CH7.10 to drain page