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authorPaolo Bonzini <pbonzini@redhat.com>2017-08-02 17:55:54 +0200
committerRadim Krčmář <rkrcmar@redhat.com>2017-08-02 22:41:02 +0200
commit3898da947bbaf9e7fd5816e825978d360028bba2 (patch)
tree5af705bb61bbc9760de0fbc3d102227f0b21fed4 /virt
parentebd28fcb55e288030abb5bca4869603b3e1f5f7c (diff)
KVM: avoid using rcu_dereference_protected
During teardown, accesses to memslots and buses are using rcu_dereference_protected with an always-true condition because these accesses are done outside the usual mutexes. This is because the last reference is gone and there cannot be any concurrent modifications, but rcu_dereference_protected is ugly and unobvious. Instead, check the refcount in kvm_get_bus and __kvm_memslots. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/kvm_main.c11
1 files changed, 4 insertions, 7 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index f3f74271f1a9..15252d723b54 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -717,10 +717,9 @@ out_err_no_srcu:
hardware_disable_all();
out_err_no_disable:
for (i = 0; i < KVM_NR_BUSES; i++)
- kfree(rcu_access_pointer(kvm->buses[i]));
+ kfree(kvm_get_bus(kvm, i));
for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++)
- kvm_free_memslots(kvm,
- rcu_dereference_protected(kvm->memslots[i], 1));
+ kvm_free_memslots(kvm, __kvm_memslots(kvm, i));
kvm_arch_free_vm(kvm);
mmdrop(current->mm);
return ERR_PTR(r);
@@ -754,9 +753,8 @@ static void kvm_destroy_vm(struct kvm *kvm)
spin_unlock(&kvm_lock);
kvm_free_irq_routing(kvm);
for (i = 0; i < KVM_NR_BUSES; i++) {
- struct kvm_io_bus *bus;
+ struct kvm_io_bus *bus = kvm_get_bus(kvm, i);
- bus = rcu_dereference_protected(kvm->buses[i], 1);
if (bus)
kvm_io_bus_destroy(bus);
kvm->buses[i] = NULL;
@@ -770,8 +768,7 @@ static void kvm_destroy_vm(struct kvm *kvm)
kvm_arch_destroy_vm(kvm);
kvm_destroy_devices(kvm);
for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++)
- kvm_free_memslots(kvm,
- rcu_dereference_protected(kvm->memslots[i], 1));
+ kvm_free_memslots(kvm, __kvm_memslots(kvm, i));
cleanup_srcu_struct(&kvm->irq_srcu);
cleanup_srcu_struct(&kvm->srcu);
kvm_arch_free_vm(kvm);