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Subject[PATCH AUTOSEL 5.1 09/51] iommu/vt-d: Fix lock inversion between iommu->lock and device_domain_lock
Date
From: Dave Jiang <dave.jiang@intel.com>

[ Upstream commit 7560cc3ca7d9d11555f80c830544e463fcdb28b8 ]

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.

[ 76.238180] dsa_bus wq0.0: dsa wq wq0.0 disabled
[ 76.248706]
[ 76.250486] ========================================================
[ 76.257113] WARNING: possible irq lock inversion dependency detected
[ 76.263736] 5.1.0-rc5+ #162 Not tainted
[ 76.267854] --------------------------------------------------------
[ 76.274485] systemd-journal/521 just changed the state of lock:
[ 76.280685] 0000000055b330f5 (device_domain_lock){..-.}, at: iommu_flush_dev_iotlb.part.63+0x29/0x90
[ 76.290099] but this lock took another, SOFTIRQ-unsafe lock in the past:
[ 76.297093] (&(&iommu->lock)->rlock){+.+.}
[ 76.297094]
[ 76.297094]
[ 76.297094] and interrupts could create inverse lock ordering between them.
[ 76.297094]
[ 76.314257]
[ 76.314257] other info that might help us debug this:
[ 76.321448] Possible interrupt unsafe locking scenario:
[ 76.321448]
[ 76.328907] CPU0 CPU1
[ 76.333777] ---- ----
[ 76.338642] lock(&(&iommu->lock)->rlock);
[ 76.343165] local_irq_disable();
[ 76.349422] lock(device_domain_lock);
[ 76.356116] lock(&(&iommu->lock)->rlock);
[ 76.363154] <Interrupt>
[ 76.366134] lock(device_domain_lock);
[ 76.370548]
[ 76.370548] *** DEADLOCK ***

Fixes: 745f2586e78e ("iommu/vt-d: Simplify function get_domain_for_dev()")
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/iommu/intel-iommu.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 0feb3f70da16..c82d5f1bd306 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -2509,6 +2509,7 @@ 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);
@@ -2524,17 +2525,16 @@ 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;
}
@@ -2544,6 +2544,7 @@ 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)) {
--
2.20.1
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