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From: Ashish Mhetre <amhetre@nvidia.com>
To: <amhetre@nvidia.com>, <joro@8bytes.org>, <will@kernel.org>,
	<robin.murphy@arm.com>, <vdumpa@nvidia.com>
Cc: <iommu@lists.linux-foundation.org>,
	<linux-kernel@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>
Subject: [PATCH 2/2] iommu/arm-smmu: Fix race condition during iommu_group creation
Date: Thu, 10 Jun 2021 09:46:54 +0530	[thread overview]
Message-ID: <1623298614-31755-3-git-send-email-amhetre@nvidia.com> (raw)
In-Reply-To: <1623298614-31755-1-git-send-email-amhetre@nvidia.com>

From: Krishna Reddy <vdumpa@nvidia.com>

iommu_group is getting created more than once during asynchronous multiple
display heads(devices) probe on Tegra194 SoC. All the display heads share
same SID and are expected to be in same iommu_group.
As arm_smmu_device_group() is not protecting group creation across devices,
it is leading to multiple groups creation across devices with same SID and
subsequent IOMMU faults.
Fix this by protecting group creation with smmu->stream_map_mutex.

Signed-off-by: Krishna Reddy <vdumpa@nvidia.com>
---
 drivers/iommu/arm/arm-smmu/arm-smmu.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
index 6f72c4d..21af179 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
@@ -1458,6 +1458,7 @@ static struct iommu_group *arm_smmu_device_group(struct device *dev)
 	struct iommu_group *group = NULL;
 	int i, idx;
 
+	mutex_lock(&smmu->stream_map_mutex);
 	for_each_cfg_sme(cfg, fwspec, i, idx) {
 		if (group && smmu->s2crs[idx].group &&
 		    group != smmu->s2crs[idx].group)
@@ -1466,8 +1467,10 @@ static struct iommu_group *arm_smmu_device_group(struct device *dev)
 		group = smmu->s2crs[idx].group;
 	}
 
-	if (group)
+	if (group) {
+		mutex_unlock(&smmu->stream_map_mutex);
 		return iommu_group_ref_get(group);
+	}
 
 	if (dev_is_pci(dev))
 		group = pci_device_group(dev);
@@ -1481,6 +1484,7 @@ static struct iommu_group *arm_smmu_device_group(struct device *dev)
 		for_each_cfg_sme(cfg, fwspec, i, idx)
 			smmu->s2crs[idx].group = group;
 
+	mutex_unlock(&smmu->stream_map_mutex);
 	return group;
 }
 
-- 
2.7.4


      parent reply	other threads:[~2021-06-10  4:17 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-10  4:16 [PATCH 0/2] iommu/arm-smmu: Fix races in iommu domain/group creation Ashish Mhetre
2021-06-10  4:16 ` [PATCH 1/2] iommu: Fix race condition during default domain allocation Ashish Mhetre
2021-06-11 10:45   ` Will Deacon
2021-06-11 12:49     ` Robin Murphy
2021-06-17  5:51       ` Ashish Mhetre
2021-06-17 17:49         ` Will Deacon
2021-06-11 18:30     ` Krishna Reddy
2021-06-10  4:16 ` Ashish Mhetre [this message]

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