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Message-ID: <156089173816.31375.3686352361646791464@skylake-alporthouse-com>
Date: Tue, 18 Jun 2019 22:02:18 +0100
From: Chris Wilson <chris@...is-wilson.co.uk>
To: Lu Baolu <baolu.lu@...ux.intel.com>, dwmw2@...radead.org,
joro@...tes.org
Cc: ashok.raj@...el.com, jacob.jun.pan@...ux.intel.com,
Kevin Tian <kevin.tian@...el.com>,
iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
Dave Jiang <dave.jiang@...el.com>
Subject: Re: [PATCH 1/2] iommu/vt-d: Fix lock inversion between iommu->lock and
device_domain_lock
Quoting Lu Baolu (2019-05-21 08:30:15)
> From: Dave Jiang <dave.jiang@...el.com>
>
> Lockdep debug reported lock inversion related with the iommu code
> caused by dmar_insert_one_dev_info() grabbing the iommu->lock and
> the device_domain_lock out of order versus the code path in
> iommu_flush_dev_iotlb(). Expanding the scope of the iommu->lock and
> reversing the order of lock acquisition fixes the issue.
Which of course violates the property that device_domain_lock is the
outer lock...
<4>[ 1.252997] ======================================================
<4>[ 1.252999] WARNING: possible circular locking dependency detected
<4>[ 1.253002] 5.2.0-rc5-CI-CI_DRM_6299+ #1 Not tainted
<4>[ 1.253004] ------------------------------------------------------
<4>[ 1.253006] swapper/0/1 is trying to acquire lock:
<4>[ 1.253009] 0000000091462475 (&(&iommu->lock)->rlock){+.+.}, at: domain_context_mapping_one+0xa0/0x4f0
<4>[ 1.253015]
but task is already holding lock:
<4>[ 1.253017] 0000000069266737 (device_domain_lock){....}, at: domain_context_mapping_one+0x88/0x4f0
<4>[ 1.253021]
which lock already depends on the new lock.
<4>[ 1.253024]
the existing dependency chain (in reverse order) is:
<4>[ 1.253027]
-> #1 (device_domain_lock){....}:
<4>[ 1.253031] _raw_spin_lock_irqsave+0x33/0x50
<4>[ 1.253034] dmar_insert_one_dev_info+0xb8/0x520
<4>[ 1.253036] set_domain_for_dev+0x66/0xf0
<4>[ 1.253039] iommu_prepare_identity_map+0x48/0x95
<4>[ 1.253042] intel_iommu_init+0xfd8/0x138d
<4>[ 1.253045] pci_iommu_init+0x11/0x3a
<4>[ 1.253048] do_one_initcall+0x58/0x300
<4>[ 1.253051] kernel_init_freeable+0x2c0/0x359
<4>[ 1.253054] kernel_init+0x5/0x100
<4>[ 1.253056] ret_from_fork+0x3a/0x50
<4>[ 1.253058]
-> #0 (&(&iommu->lock)->rlock){+.+.}:
<4>[ 1.253062] lock_acquire+0xa6/0x1c0
<4>[ 1.253064] _raw_spin_lock+0x2a/0x40
<4>[ 1.253067] domain_context_mapping_one+0xa0/0x4f0
<4>[ 1.253070] pci_for_each_dma_alias+0x2b/0x160
<4>[ 1.253072] dmar_insert_one_dev_info+0x44e/0x520
<4>[ 1.253075] set_domain_for_dev+0x66/0xf0
<4>[ 1.253077] iommu_prepare_identity_map+0x48/0x95
<4>[ 1.253080] intel_iommu_init+0xfd8/0x138d
<4>[ 1.253082] pci_iommu_init+0x11/0x3a
<4>[ 1.253084] do_one_initcall+0x58/0x300
<4>[ 1.253086] kernel_init_freeable+0x2c0/0x359
<4>[ 1.253089] kernel_init+0x5/0x100
<4>[ 1.253091] ret_from_fork+0x3a/0x50
<4>[ 1.253093]
other info that might help us debug this:
<4>[ 1.253095] Possible unsafe locking scenario:
<4>[ 1.253095] CPU0 CPU1
<4>[ 1.253095] ---- ----
<4>[ 1.253095] lock(device_domain_lock);
<4>[ 1.253095] lock(&(&iommu->lock)->rlock);
<4>[ 1.253095] lock(device_domain_lock);
<4>[ 1.253095] lock(&(&iommu->lock)->rlock);
<4>[ 1.253095]
*** DEADLOCK ***
<4>[ 1.253095] 2 locks held by swapper/0/1:
<4>[ 1.253095] #0: 0000000076465a1e (dmar_global_lock){++++}, at: intel_iommu_init+0x1d3/0x138d
<4>[ 1.253095] #1: 0000000069266737 (device_domain_lock){....}, at: domain_context_mapping_one+0x88/0x4f0
<4>[ 1.253095]
stack backtrace:
<4>[ 1.253095] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.2.0-rc5-CI-CI_DRM_6299+ #1
<4>[ 1.253095] Hardware name: /NUC5i7RYB, BIOS RYBDWi35.86A.0362.2017.0118.0940 01/18/2017
<4>[ 1.253095] Call Trace:
<4>[ 1.253095] dump_stack+0x67/0x9b
<4>[ 1.253095] print_circular_bug+0x1c8/0x2b0
<4>[ 1.253095] __lock_acquire+0x1ce9/0x24c0
<4>[ 1.253095] ? lock_acquire+0xa6/0x1c0
<4>[ 1.253095] lock_acquire+0xa6/0x1c0
<4>[ 1.253095] ? domain_context_mapping_one+0xa0/0x4f0
<4>[ 1.253095] _raw_spin_lock+0x2a/0x40
<4>[ 1.253095] ? domain_context_mapping_one+0xa0/0x4f0
<4>[ 1.253095] domain_context_mapping_one+0xa0/0x4f0
<4>[ 1.253095] ? domain_context_mapping_one+0x4f0/0x4f0
<4>[ 1.253095] pci_for_each_dma_alias+0x2b/0x160
<4>[ 1.253095] dmar_insert_one_dev_info+0x44e/0x520
<4>[ 1.253095] set_domain_for_dev+0x66/0xf0
<4>[ 1.253095] iommu_prepare_identity_map+0x48/0x95
<4>[ 1.253095] intel_iommu_init+0xfd8/0x138d
<4>[ 1.253095] ? set_debug_rodata+0xc/0xc
<4>[ 1.253095] ? set_debug_rodata+0xc/0xc
<4>[ 1.253095] ? e820__memblock_setup+0x5b/0x5b
<4>[ 1.253095] ? pci_iommu_init+0x11/0x3a
<4>[ 1.253095] ? set_debug_rodata+0xc/0xc
<4>[ 1.253095] pci_iommu_init+0x11/0x3a
<4>[ 1.253095] do_one_initcall+0x58/0x300
<4>[ 1.253095] kernel_init_freeable+0x2c0/0x359
<4>[ 1.253095] ? rest_init+0x250/0x250
<4>[ 1.253095] kernel_init+0x5/0x100
<4>[ 1.253095] ret_from_fork+0x3a/0x50
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