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authorPeter Xu <peterx@redhat.com>2019-06-21 10:32:05 +0800
committerJoerg Roedel <jroedel@suse.de>2019-06-22 21:19:58 +0200
commit0aafc8ae665f89b9031a914f80f5e58825b33021 (patch)
treeb4c6073696482bd1e805cc2c65e9f66797853c35
parent9e0babf2c06c73cda2c0cd37a1653d823adb40ec (diff)
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Revert "iommu/vt-d: Fix lock inversion between iommu->lock and device_domain_lock"
This reverts commit 7560cc3ca7d9d11555f80c830544e463fcdb28b8. With 5.2.0-rc5 I can easily trigger this with lockdep and iommu=pt: ====================================================== WARNING: possible circular locking dependency detected 5.2.0-rc5 #78 Not tainted ------------------------------------------------------ swapper/0/1 is trying to acquire lock: 00000000ea2b3beb (&(&iommu->lock)->rlock){+.+.}, at: domain_context_mapping_one+0xa5/0x4e0 but task is already holding lock: 00000000a681907b (device_domain_lock){....}, at: domain_context_mapping_one+0x8d/0x4e0 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (device_domain_lock){....}: _raw_spin_lock_irqsave+0x3c/0x50 dmar_insert_one_dev_info+0xbb/0x510 domain_add_dev_info+0x50/0x90 dev_prepare_static_identity_mapping+0x30/0x68 intel_iommu_init+0xddd/0x1422 pci_iommu_init+0x16/0x3f do_one_initcall+0x5d/0x2b4 kernel_init_freeable+0x218/0x2c1 kernel_init+0xa/0x100 ret_from_fork+0x3a/0x50 -> #0 (&(&iommu->lock)->rlock){+.+.}: lock_acquire+0x9e/0x170 _raw_spin_lock+0x25/0x30 domain_context_mapping_one+0xa5/0x4e0 pci_for_each_dma_alias+0x30/0x140 dmar_insert_one_dev_info+0x3b2/0x510 domain_add_dev_info+0x50/0x90 dev_prepare_static_identity_mapping+0x30/0x68 intel_iommu_init+0xddd/0x1422 pci_iommu_init+0x16/0x3f do_one_initcall+0x5d/0x2b4 kernel_init_freeable+0x218/0x2c1 kernel_init+0xa/0x100 ret_from_fork+0x3a/0x50 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(device_domain_lock); lock(&(&iommu->lock)->rlock); lock(device_domain_lock); lock(&(&iommu->lock)->rlock); *** DEADLOCK *** 2 locks held by swapper/0/1: #0: 00000000033eb13d (dmar_global_lock){++++}, at: intel_iommu_init+0x1e0/0x1422 #1: 00000000a681907b (device_domain_lock){....}, at: domain_context_mapping_one+0x8d/0x4e0 stack backtrace: CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.2.0-rc5 #78 Hardware name: LENOVO 20KGS35G01/20KGS35G01, BIOS N23ET50W (1.25 ) 06/25/2018 Call Trace: dump_stack+0x85/0xc0 print_circular_bug.cold.57+0x15c/0x195 __lock_acquire+0x152a/0x1710 lock_acquire+0x9e/0x170 ? domain_context_mapping_one+0xa5/0x4e0 _raw_spin_lock+0x25/0x30 ? domain_context_mapping_one+0xa5/0x4e0 domain_context_mapping_one+0xa5/0x4e0 ? domain_context_mapping_one+0x4e0/0x4e0 pci_for_each_dma_alias+0x30/0x140 dmar_insert_one_dev_info+0x3b2/0x510 domain_add_dev_info+0x50/0x90 dev_prepare_static_identity_mapping+0x30/0x68 intel_iommu_init+0xddd/0x1422 ? printk+0x58/0x6f ? lockdep_hardirqs_on+0xf0/0x180 ? do_early_param+0x8e/0x8e ? e820__memblock_setup+0x63/0x63 pci_iommu_init+0x16/0x3f do_one_initcall+0x5d/0x2b4 ? do_early_param+0x8e/0x8e ? rcu_read_lock_sched_held+0x55/0x60 ? do_early_param+0x8e/0x8e kernel_init_freeable+0x218/0x2c1 ? rest_init+0x230/0x230 kernel_init+0xa/0x100 ret_from_fork+0x3a/0x50 domain_context_mapping_one() is taking device_domain_lock first then iommu lock, while dmar_insert_one_dev_info() is doing the reverse. That should be introduced by commit: 7560cc3ca7d9 ("iommu/vt-d: Fix lock inversion between iommu->lock and device_domain_lock", 2019-05-27) So far I still cannot figure out how the previous deadlock was triggered (I cannot find iommu lock taken before calling of iommu_flush_dev_iotlb()), however I'm pretty sure that that change should be incomplete at least because it does not fix all the places so we're still taking the locks in different orders, while reverting that commit is very clean to me so far that we should always take device_domain_lock first then the iommu lock. We can continue to try to find the real culprit mentioned in 7560cc3ca7d9, but for now I think we should revert it to fix current breakage. CC: Joerg Roedel <joro@8bytes.org> CC: Lu Baolu <baolu.lu@linux.intel.com> CC: dave.jiang@intel.com Signed-off-by: Peter Xu <peterx@redhat.com> Tested-by: Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by: Joerg Roedel <jroedel@suse.de>
-rw-r--r--drivers/iommu/intel-iommu.c7
1 files changed, 3 insertions, 4 deletions
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 56297298d6ee..162b3236e72c 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -2504,7 +2504,6 @@ static struct dmar_domain *dmar_insert_one_dev_info(struct intel_iommu *iommu,
}
}
- spin_lock(&iommu->lock);
spin_lock_irqsave(&device_domain_lock, flags);
if (dev)
found = find_domain(dev);
@@ -2520,16 +2519,17 @@ static struct dmar_domain *dmar_insert_one_dev_info(struct intel_iommu *iommu,
if (found) {
spin_unlock_irqrestore(&device_domain_lock, flags);
- spin_unlock(&iommu->lock);
free_devinfo_mem(info);
/* Caller must free the original domain */
return found;
}
+ spin_lock(&iommu->lock);
ret = domain_attach_iommu(domain, iommu);
+ spin_unlock(&iommu->lock);
+
if (ret) {
spin_unlock_irqrestore(&device_domain_lock, flags);
- spin_unlock(&iommu->lock);
free_devinfo_mem(info);
return NULL;
}
@@ -2539,7 +2539,6 @@ static struct dmar_domain *dmar_insert_one_dev_info(struct intel_iommu *iommu,
if (dev)
dev->archdata.iommu = info;
spin_unlock_irqrestore(&device_domain_lock, flags);
- spin_unlock(&iommu->lock);
/* PASID table is mandatory for a PCI device in scalable mode. */
if (dev && dev_is_pci(dev) && sm_supported(iommu)) {