From fae3a3536a6fecedebd49fa847f810e599bfb132 Mon Sep 17 00:00:00 2001
From: Sheng Yang <sheng@linux.intel.com>
Date: Tue, 15 Dec 2009 10:28:07 +0800
Subject: [PATCH] KVM: Fix possible circular locking in
kvm_vm_ioctl_assign_device()
One possible order is:
KVM_CREATE_IRQCHIP ioctl(took kvm->lock) -> kvm_iobus_register_dev() ->
down_write(kvm->slots_lock).
The other one is in kvm_vm_ioctl_assign_device(), which take kvm->slots_lock
first, then kvm->lock.
Update the comment of lock order as well.
Observe it due to kernel locking debug warnings.
Cc: stable@kernel.org
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
---
virt/kvm/assigned-dev.c | 6 +++---
virt/kvm/kvm_main.c | 2 +-
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c
index fd9c097b760a..f73de631e3ee 100644
--- a/virt/kvm/assigned-dev.c
+++ b/virt/kvm/assigned-dev.c
@@ -508,8 +508,8 @@ 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);
+ down_read(&kvm->slots_lock);
match = kvm_find_assigned_dev(&kvm->arch.assigned_dev_head,
assigned_dev->assigned_dev_id);
@@ -573,8 +573,8 @@ static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
}
out:
- mutex_unlock(&kvm->lock);
up_read(&kvm->slots_lock);
+ mutex_unlock(&kvm->lock);
return r;
out_list_del:
list_del(&match->list);
@@ -585,8 +585,8 @@ out_put:
pci_dev_put(dev);
out_free:
kfree(match);
- mutex_unlock(&kvm->lock);
up_read(&kvm->slots_lock);
+ mutex_unlock(&kvm->lock);
return r;
}
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b5af88167613..7db071ba466c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -64,7 +64,7 @@ MODULE_LICENSE("GPL");
/*
* Ordering of locks:
*
- * kvm->slots_lock --> kvm->lock --> kvm->irq_lock
+ * kvm->lock --> kvm->slots_lock --> kvm->irq_lock
*/
DEFINE_SPINLOCK(kvm_lock);
--
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