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| author | Paolo Bonzini <pbonzini@redhat.com> | 2017-08-02 17:55:54 +0200 |
|---|---|---|
| committer | Radim Krčmář <rkrcmar@redhat.com> | 2017-08-02 22:41:02 +0200 |
| commit | 3898da947bbaf9e7fd5816e825978d360028bba2 (patch) | |
| tree | 5af705bb61bbc9760de0fbc3d102227f0b21fed4 /virt/kvm | |
| parent | ebd28fcb55e288030abb5bca4869603b3e1f5f7c (diff) | |
| download | linux-3898da947bbaf9e7fd5816e825978d360028bba2.tar.bz2 | |
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/kvm')
| -rw-r--r-- | virt/kvm/kvm_main.c | 11 |
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); |