From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 22 Mar 2018 16:22:36 +0100
Subject: iommu/amd: Split irq_lookup_table out of the amd_iommu_devtable_lock
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git
Git-commit: 501acb88374b6ac1ac87461ec4e17540c1c33f20
Patch-mainline: Queued in subsystem maintainer repository
References: SLE Realtime Extension

Upstream commit ea6166f4b83e9cfba1c18f46a764d50045682fe5

The function get_irq_table() reads/writes irq_lookup_table while holding
the amd_iommu_devtable_lock. It also modifies
amd_iommu_dev_table[].data[2].
set_dte_entry() is using amd_iommu_dev_table[].data[0|1] (under the
domain->lock) so it should be okay. The access to the iommu is
serialized with its own (iommu's) lock.

So split out get_irq_table() out of amd_iommu_devtable_lock's lock.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Mike Galbraith <mgalbraith@suse.de>
---
 drivers/iommu/amd_iommu.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -81,6 +81,7 @@
 
 static DEFINE_RWLOCK(amd_iommu_devtable_lock);
 static DEFINE_SPINLOCK(pd_bitmap_lock);
+static DEFINE_SPINLOCK(iommu_table_lock);
 
 /* List of all available dev_data structures */
 static LLIST_HEAD(dev_data_list);
@@ -3798,7 +3799,7 @@ static struct irq_remap_table *alloc_irq
 	unsigned long flags;
 	u16 alias;
 
-	write_lock_irqsave(&amd_iommu_devtable_lock, flags);
+	spin_lock_irqsave(&iommu_table_lock, flags);
 
 	iommu = amd_iommu_rlookup_table[devid];
 	if (!iommu)
@@ -3863,7 +3864,7 @@ static struct irq_remap_table *alloc_irq
 	iommu_completion_wait(iommu);
 
 out_unlock:
-	write_unlock_irqrestore(&amd_iommu_devtable_lock, flags);
+	spin_unlock_irqrestore(&iommu_table_lock, flags);
 
 	return table;
 }