From 3898da947bbaf9e7fd5816e825978d360028bba2 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Wed, 2 Aug 2017 17:55:54 +0200 Subject: KVM: avoid using rcu_dereference_protected MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Radim Krčmář --- include/linux/kvm_host.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'include/linux/kvm_host.h') diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 890b706d1943..21a6fd6c44af 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -477,7 +477,8 @@ struct kvm { static inline struct kvm_io_bus *kvm_get_bus(struct kvm *kvm, enum kvm_bus idx) { return srcu_dereference_check(kvm->buses[idx], &kvm->srcu, - lockdep_is_held(&kvm->slots_lock)); + lockdep_is_held(&kvm->slots_lock) || + !refcount_read(&kvm->users_count)); } static inline struct kvm_vcpu *kvm_get_vcpu(struct kvm *kvm, int i) @@ -570,7 +571,8 @@ void kvm_put_kvm(struct kvm *kvm); static inline struct kvm_memslots *__kvm_memslots(struct kvm *kvm, int as_id) { return srcu_dereference_check(kvm->memslots[as_id], &kvm->srcu, - lockdep_is_held(&kvm->slots_lock)); + lockdep_is_held(&kvm->slots_lock) || + !refcount_read(&kvm->users_count)); } static inline struct kvm_memslots *kvm_memslots(struct kvm *kvm) -- cgit