[PATCH 1/7] iommu/arm-smmu: avoid calling request_irq in atomic context

[Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>]

From: Mitchel Humpherys <mitchelh-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>

request_irq shouldn't be called from atomic context since it might
sleep, but we're calling it with a spinlock held, resulting in:

    [    9.172202] BUG: sleeping function called from invalid context at kernel/mm/slub.c:926
    [    9.182989] in_atomic(): 1, irqs_disabled(): 128, pid: 1, name: swapper/0
    [    9.189762] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G        W    3.10.40-gbc1b510b-38437-g55831d3bd9-dirty #97
    [    9.199757] [<c020c448>] (unwind_backtrace+0x0/0x11c) from [<c02097d0>] (show_stack+0x10/0x14)
    [    9.208346] [<c02097d0>] (show_stack+0x10/0x14) from [<c0301d74>] (kmem_cache_alloc_trace+0x3c/0x210)
    [    9.217543] [<c0301d74>] (kmem_cache_alloc_trace+0x3c/0x210) from [<c0276a48>] (request_threaded_irq+0x88/0x11c)
    [    9.227702] [<c0276a48>] (request_threaded_irq+0x88/0x11c) from [<c0931ca4>] (arm_smmu_attach_dev+0x188/0x858)
    [    9.237686] [<c0931ca4>] (arm_smmu_attach_dev+0x188/0x858) from [<c0212cd8>] (arm_iommu_attach_device+0x18/0xd0)
    [    9.247837] [<c0212cd8>] (arm_iommu_attach_device+0x18/0xd0) from [<c093314c>] (arm_smmu_test_probe+0x68/0xd4)
    [    9.257823] [<c093314c>] (arm_smmu_test_probe+0x68/0xd4) from [<c05aadd0>] (driver_probe_device+0x12c/0x330)
    [    9.267629] [<c05aadd0>] (driver_probe_device+0x12c/0x330) from [<c05ab080>] (__driver_attach+0x68/0x8c)
    [    9.277090] [<c05ab080>] (__driver_attach+0x68/0x8c) from [<c05a92d4>] (bus_for_each_dev+0x70/0x84)
    [    9.286118] [<c05a92d4>] (bus_for_each_dev+0x70/0x84) from [<c05aa3b0>] (bus_add_driver+0x100/0x244)
    [    9.295233] [<c05aa3b0>] (bus_add_driver+0x100/0x244) from [<c05ab5d0>] (driver_register+0x9c/0x124)
    [    9.304347] [<c05ab5d0>] (driver_register+0x9c/0x124) from [<c0933088>] (arm_smmu_test_init+0x14/0x38)
    [    9.313635] [<c0933088>] (arm_smmu_test_init+0x14/0x38) from [<c0200618>] (do_one_initcall+0xb8/0x160)
    [    9.322926] [<c0200618>] (do_one_initcall+0xb8/0x160) from [<c1200b7c>] (kernel_init_freeable+0x108/0x1cc)
    [    9.332564] [<c1200b7c>] (kernel_init_freeable+0x108/0x1cc) from [<c0b924b0>] (kernel_init+0xc/0xe4)
    [    9.341675] [<c0b924b0>] (kernel_init+0xc/0xe4) from [<c0205e38>] (ret_from_fork+0x14/0x3c)

Fix this by moving the request_irq out of the critical section. This
should be okay since smmu_domain->smmu is still being protected by the
critical section. Also, we still don't program the Stream Match Register
until after registering our interrupt handler so we shouldn't be missing
any interrupts.

Signed-off-by: Mitchel Humpherys <mitchelh-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
[will: code cleanup and fixed request_irq token parameter]
Signed-off-by: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>
---
 drivers/iommu/arm-smmu.c | 47 +++++++++++++++++++++++++----------------------
 1 file changed, 25 insertions(+), 22 deletions(-)

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index ca18d6d42a9b..98fcd87cbacb 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -868,10 +868,15 @@ static void arm_smmu_init_context_bank(struct arm_smmu_domain *smmu_domain)
 static int arm_smmu_init_domain_context(struct iommu_domain *domain,
 					struct arm_smmu_device *smmu)
 {
-	int irq, ret, start;
+	int irq, start, ret = 0;
+	unsigned long flags;
 	struct arm_smmu_domain *smmu_domain = domain->priv;
 	struct arm_smmu_cfg *cfg = &smmu_domain->cfg;
 
+	spin_lock_irqsave(&smmu_domain->lock, flags);
+	if (smmu_domain->smmu)
+		goto out_unlock;
+
 	if (smmu->features & ARM_SMMU_FEAT_TRANS_NESTED) {
 		/*
 		 * We will likely want to change this if/when KVM gets
@@ -890,7 +895,7 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
 	ret = __arm_smmu_alloc_bitmap(smmu->context_map, start,
 				      smmu->num_context_banks);
 	if (IS_ERR_VALUE(ret))
-		return ret;
+		goto out_unlock;
 
 	cfg->cbndx = ret;
 	if (smmu->version == 1) {
@@ -900,6 +905,10 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
 		cfg->irptndx = cfg->cbndx;
 	}
 
+	ACCESS_ONCE(smmu_domain->smmu) = smmu;
+	arm_smmu_init_context_bank(smmu_domain);
+	spin_unlock_irqrestore(&smmu_domain->lock, flags);
+
 	irq = smmu->irqs[smmu->num_global_irqs + cfg->irptndx];
 	ret = request_irq(irq, arm_smmu_context_fault, IRQF_SHARED,
 			  "arm-smmu-context-fault", domain);
@@ -907,15 +916,12 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
 		dev_err(smmu->dev, "failed to request context IRQ %d (%u)\n",
 			cfg->irptndx, irq);
 		cfg->irptndx = INVALID_IRPTNDX;
-		goto out_free_context;
 	}
 
-	smmu_domain->smmu = smmu;
-	arm_smmu_init_context_bank(smmu_domain);
 	return 0;
 
-out_free_context:
-	__arm_smmu_free_bitmap(smmu->context_map, cfg->cbndx);
+out_unlock:
+	spin_unlock_irqrestore(&smmu_domain->lock, flags);
 	return ret;
 }
 
@@ -1172,11 +1178,10 @@ static void arm_smmu_domain_remove_master(struct arm_smmu_domain *smmu_domain,
 
 static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 {
-	int ret = -EINVAL;
+	int ret;
 	struct arm_smmu_domain *smmu_domain = domain->priv;
-	struct arm_smmu_device *smmu;
+	struct arm_smmu_device *smmu, *dom_smmu;
 	struct arm_smmu_master_cfg *cfg;
-	unsigned long flags;
 
 	smmu = dev_get_master_dev(dev)->archdata.iommu;
 	if (!smmu) {
@@ -1188,20 +1193,22 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 	 * Sanity check the domain. We don't support domains across
 	 * different SMMUs.
 	 */
-	spin_lock_irqsave(&smmu_domain->lock, flags);
-	if (!smmu_domain->smmu) {
+	dom_smmu = ACCESS_ONCE(smmu_domain->smmu);
+	if (!dom_smmu) {
 		/* Now that we have a master, we can finalise the domain */
 		ret = arm_smmu_init_domain_context(domain, smmu);
 		if (IS_ERR_VALUE(ret))
-			goto err_unlock;
-	} else if (smmu_domain->smmu != smmu) {
+			return ret;
+
+		dom_smmu = smmu_domain->smmu;
+	}
+
+	if (dom_smmu != smmu) {
 		dev_err(dev,
 			"cannot attach to SMMU %s whilst already attached to domain on SMMU %s\n",
-			dev_name(smmu_domain->smmu->dev),
-			dev_name(smmu->dev));
-		goto err_unlock;
+			dev_name(smmu_domain->smmu->dev), dev_name(smmu->dev));
+		return -EINVAL;
 	}
-	spin_unlock_irqrestore(&smmu_domain->lock, flags);
 
 	/* Looks ok, so add the device to the domain */
 	cfg = find_smmu_master_cfg(smmu_domain->smmu, dev);
@@ -1209,10 +1216,6 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 		return -ENODEV;
 
 	return arm_smmu_domain_add_master(smmu_domain, cfg);
-
-err_unlock:
-	spin_unlock_irqrestore(&smmu_domain->lock, flags);
-	return ret;
 }
 
 static void arm_smmu_detach_dev(struct iommu_domain *domain, struct device *dev)
-- 
2.1.0