evie/android_kernel_oneplus_msm8998
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iommu/arm-smmu: Protect against concurrent attach from different domains

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Currently we're relying on the smmu_domain->lock for synchronizing
attach and detach.  This is a problem because each domain has its own
smmu_domain->lock, so if multiple different domains try to attach to the
same device at the same time, they'll be racing.

Fix the race by holding a lock that's part of the smmu
structure (attach_lock should do just fine).

The test case that uncovered this was:

    # cd /sys/kernel/debug/iommu/tests/soc:qcom,msm-audio-ion/
    # while :; do cat profiling; done &
    # while :; do cat profiling; done &

Change-Id: I8a60cdc214c91967aff63882e3a7280865ffda9e
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>
This commit is contained in:
Mitchel Humpherys 2015-06-26 19:11:53 -07:00 • committed by David Keitel
parent 49b6182ba5
commit 7543efb4bc
1 changed files with 10 additions and 9 deletions
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19
drivers/iommu/arm-smmu.c
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@ -381,6 +381,7 @@ struct arm_smmu_device {
struct regulator *gdsc;
/* Protects against domains attaching to the same SMMU concurrently */
struct mutex attach_lock;
unsigned int attach_count;
@ -1538,13 +1539,14 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
return -ENXIO;
}
mutex_lock(&smmu->attach_lock);
if (dev->archdata.iommu) {
dev_err(dev, "already attached to IOMMU domain\n");
mutex_unlock(&smmu->attach_lock);
mutex_unlock(&smmu_domain->init_mutex);
return -EEXIST;
}
mutex_lock(&smmu->attach_lock);
if (!smmu->attach_count++) {
/*
* We need an extra power vote if we can't retain register
@ -1564,7 +1566,6 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
} else {
arm_smmu_enable_clocks(smmu);
}
mutex_unlock(&smmu->attach_lock);
/* Ensure that the domain is finalised */
ret = arm_smmu_init_domain_context(domain, smmu);
@ -1604,6 +1605,7 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
goto err_destroy_domain_context;
dev->archdata.iommu = domain;
arm_smmu_disable_clocks(smmu);
mutex_unlock(&smmu->attach_lock);
mutex_unlock(&smmu_domain->init_mutex);
return ret;
@ -1611,12 +1613,11 @@ err_destroy_domain_context:
arm_smmu_destroy_domain_context(domain);
err_disable_clocks:
arm_smmu_disable_clocks(smmu);
mutex_unlock(&smmu_domain->init_mutex);
mutex_lock(&smmu->attach_lock);
if (!--smmu->attach_count &&
(!(smmu->options & ARM_SMMU_OPT_REGISTER_SAVE) || atomic_ctx))
arm_smmu_disable_regulators(smmu);
mutex_unlock(&smmu->attach_lock);
mutex_unlock(&smmu_domain->init_mutex);
return ret;
}
@ -1648,18 +1649,18 @@ static void arm_smmu_detach_dev(struct iommu_domain *domain, struct device *dev)
return;
}
mutex_lock(&smmu->attach_lock);
cfg = find_smmu_master_cfg(dev);
if (!cfg) {
mutex_unlock(&smmu_domain->init_mutex);
return;
}
if (!cfg)
goto unlock;
dev->archdata.iommu = NULL;
arm_smmu_domain_remove_master(smmu_domain, cfg);
arm_smmu_destroy_domain_context(domain);
mutex_lock(&smmu->attach_lock);
if (!--smmu->attach_count)
arm_smmu_power_off(smmu, atomic_ctx);
unlock:
mutex_unlock(&smmu->attach_lock);
mutex_unlock(&smmu_domain->init_mutex);
}