From: Scott Wood <swood@redhat.com>
Date: Sun, 21 Jan 2018 03:28:54 -0600
Subject: [PATCH 1/3] iommu/amd: Use raw locks on atomic context paths
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.16/older/patches-4.16.8-rt3.tar.xz

Upstream commit 27790398c2aed917828dc3c6f81240d57f1584c9

Several functions in this driver are called from atomic context,
and thus raw locks must be used in order to be safe on PREEMPT_RT.

This includes paths that must wait for command completion, which is
a potential PREEMPT_RT latency concern but not easily avoidable.

Signed-off-by: Scott Wood <swood@redhat.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 drivers/iommu/amd_iommu.c       |   30 +++++++++++++++---------------
 drivers/iommu/amd_iommu_init.c  |    2 +-
 drivers/iommu/amd_iommu_types.h |    4 ++--
 3 files changed, 18 insertions(+), 18 deletions(-)

--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -1056,9 +1056,9 @@ static int iommu_queue_command_sync(stru
 	unsigned long flags;
 	int ret;
 
-	spin_lock_irqsave(&iommu->lock, flags);
+	raw_spin_lock_irqsave(&iommu->lock, flags);
 	ret = __iommu_queue_command_sync(iommu, cmd, sync);
-	spin_unlock_irqrestore(&iommu->lock, flags);
+	raw_spin_unlock_irqrestore(&iommu->lock, flags);
 
 	return ret;
 }
@@ -1084,7 +1084,7 @@ static int iommu_completion_wait(struct
 
 	build_completion_wait(&cmd, (u64)&iommu->cmd_sem);
 
-	spin_lock_irqsave(&iommu->lock, flags);
+	raw_spin_lock_irqsave(&iommu->lock, flags);
 
 	iommu->cmd_sem = 0;
 
@@ -1095,7 +1095,7 @@ static int iommu_completion_wait(struct
 	ret = wait_on_sem(&iommu->cmd_sem);
 
 out_unlock:
-	spin_unlock_irqrestore(&iommu->lock, flags);
+	raw_spin_unlock_irqrestore(&iommu->lock, flags);
 
 	return ret;
 }
@@ -3627,7 +3627,7 @@ static struct irq_remap_table *get_irq_t
 		goto out_unlock;
 
 	/* Initialize table spin-lock */
-	spin_lock_init(&table->lock);
+	raw_spin_lock_init(&table->lock);
 
 	if (ioapic)
 		/* Keep the first 32 indexes free for IOAPIC interrupts */
@@ -3689,7 +3689,7 @@ static int alloc_irq_index(u16 devid, in
 	if (align)
 		alignment = roundup_pow_of_two(count);
 
-	spin_lock_irqsave(&table->lock, flags);
+	raw_spin_lock_irqsave(&table->lock, flags);
 
 	/* Scan table for free entries */
 	for (index = ALIGN(table->min_index, alignment), c = 0;
@@ -3716,7 +3716,7 @@ static int alloc_irq_index(u16 devid, in
 	index = -ENOSPC;
 
 out:
-	spin_unlock_irqrestore(&table->lock, flags);
+	raw_spin_unlock_irqrestore(&table->lock, flags);
 
 	return index;
 }
@@ -3737,7 +3737,7 @@ static int modify_irte_ga(u16 devid, int
 	if (!table)
 		return -ENOMEM;
 
-	spin_lock_irqsave(&table->lock, flags);
+	raw_spin_lock_irqsave(&table->lock, flags);
 
 	entry = (struct irte_ga *)table->table;
 	entry = &entry[index];
@@ -3748,7 +3748,7 @@ static int modify_irte_ga(u16 devid, int
 	if (data)
 		data->ref = entry;
 
-	spin_unlock_irqrestore(&table->lock, flags);
+	raw_spin_unlock_irqrestore(&table->lock, flags);
 
 	iommu_flush_irt(iommu, devid);
 	iommu_completion_wait(iommu);
@@ -3770,9 +3770,9 @@ static int modify_irte(u16 devid, int in
 	if (!table)
 		return -ENOMEM;
 
-	spin_lock_irqsave(&table->lock, flags);
+	raw_spin_lock_irqsave(&table->lock, flags);
 	table->table[index] = irte->val;
-	spin_unlock_irqrestore(&table->lock, flags);
+	raw_spin_unlock_irqrestore(&table->lock, flags);
 
 	iommu_flush_irt(iommu, devid);
 	iommu_completion_wait(iommu);
@@ -3794,9 +3794,9 @@ static void free_irte(u16 devid, int ind
 	if (!table)
 		return;
 
-	spin_lock_irqsave(&table->lock, flags);
+	raw_spin_lock_irqsave(&table->lock, flags);
 	iommu->irte_ops->clear_allocated(table, index);
-	spin_unlock_irqrestore(&table->lock, flags);
+	raw_spin_unlock_irqrestore(&table->lock, flags);
 
 	iommu_flush_irt(iommu, devid);
 	iommu_completion_wait(iommu);
@@ -4397,7 +4397,7 @@ int amd_iommu_update_ga(int cpu, bool is
 	if (!irt)
 		return -ENODEV;
 
-	spin_lock_irqsave(&irt->lock, flags);
+	raw_spin_lock_irqsave(&irt->lock, flags);
 
 	if (ref->lo.fields_vapic.guest_mode) {
 		if (cpu >= 0)
@@ -4406,7 +4406,7 @@ int amd_iommu_update_ga(int cpu, bool is
 		barrier();
 	}
 
-	spin_unlock_irqrestore(&irt->lock, flags);
+	raw_spin_unlock_irqrestore(&irt->lock, flags);
 
 	iommu_flush_irt(iommu, devid);
 	iommu_completion_wait(iommu);
--- a/drivers/iommu/amd_iommu_init.c
+++ b/drivers/iommu/amd_iommu_init.c
@@ -1474,7 +1474,7 @@ static int __init init_iommu_one(struct
 {
 	int ret;
 
-	spin_lock_init(&iommu->lock);
+	raw_spin_lock_init(&iommu->lock);
 
 	/* Add IOMMU to internal data structures */
 	list_add_tail(&iommu->list, &amd_iommu_list);
--- a/drivers/iommu/amd_iommu_types.h
+++ b/drivers/iommu/amd_iommu_types.h
@@ -408,7 +408,7 @@ extern bool amd_iommu_iotlb_sup;
 #define IRQ_TABLE_ALIGNMENT	128
 
 struct irq_remap_table {
-	spinlock_t lock;
+	raw_spinlock_t lock;
 	unsigned min_index;
 	u32 *table;
 };
@@ -490,7 +490,7 @@ struct amd_iommu {
 	int index;
 
 	/* locks the accesses to the hardware */
-	spinlock_t lock;
+	raw_spinlock_t lock;
 
 	/* Pointer to PCI device of this IOMMU */
 	struct pci_dev *dev;