[PATCH 1/1] kvm: fix circular locking dependency

[Mark McLoughlin <markmc@redhat.com>]

kvm->slots_lock is outer to kvm->lock, so take slots_lock
in kvm_vm_ioctl_assign_device() before taking kvm->lock,
rather than taking it in kvm_iommu_map_memslots().

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
---
 virt/kvm/iommu.c    |    6 ++----
 virt/kvm/kvm_main.c |    3 +++
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/virt/kvm/iommu.c b/virt/kvm/iommu.c
index e9693a2..4c40375 100644
--- a/virt/kvm/iommu.c
+++ b/virt/kvm/iommu.c
@@ -73,14 +73,13 @@ static int kvm_iommu_map_memslots(struct kvm *kvm)
 {
 	int i, r = 0;
 
-	down_read(&kvm->slots_lock);
 	for (i = 0; i < kvm->nmemslots; i++) {
 		r = kvm_iommu_map_pages(kvm, kvm->memslots[i].base_gfn,
 					kvm->memslots[i].npages);
 		if (r)
 			break;
 	}
-	up_read(&kvm->slots_lock);
+
 	return r;
 }
 
@@ -190,12 +189,11 @@ static void kvm_iommu_put_pages(struct kvm *kvm,
 static int kvm_iommu_unmap_memslots(struct kvm *kvm)
 {
 	int i;
-	down_read(&kvm->slots_lock);
+
 	for (i = 0; i < kvm->nmemslots; i++) {
 		kvm_iommu_put_pages(kvm, kvm->memslots[i].base_gfn,
 				    kvm->memslots[i].npages);
 	}
-	up_read(&kvm->slots_lock);
 
 	return 0;
 }
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 3a5a082..dc948c6 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -455,6 +455,7 @@ static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
 	struct kvm_assigned_dev_kernel *match;
 	struct pci_dev *dev;
 
+	down_read(&kvm->slots_lock);
 	mutex_lock(&kvm->lock);
 
 	match = kvm_find_assigned_dev(&kvm->arch.assigned_dev_head,
@@ -516,6 +517,7 @@ static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
 
 out:
 	mutex_unlock(&kvm->lock);
+	up_read(&kvm->slots_lock);
 	return r;
 out_list_del:
 	list_del(&match->list);
@@ -527,6 +529,7 @@ out_put:
 out_free:
 	kfree(match);
 	mutex_unlock(&kvm->lock);
+	up_read(&kvm->slots_lock);
 	return r;
 }
 #endif
-- 
1.6.0.6