From 42a90008f890afc41837dfeec1f0b1e7bcecf94a Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Wed, 11 Jan 2023 18:06:50 +0000 Subject: KVM: Ensure lockdep knows about kvm->lock vs. vcpu->mutex ordering rule Documentation/virt/kvm/locking.rst tells us that kvm->lock is taken outside vcpu->mutex. But that doesn't actually happen very often; it's only in some esoteric cases like migration with AMD SEV. This means that lockdep usually doesn't notice, and doesn't do its job of keeping us honest. Ensure that lockdep *always* knows about the ordering of these two locks, by briefly taking vcpu->mutex in kvm_vm_ioctl_create_vcpu() while kvm->lock is held. Signed-off-by: David Woodhouse Message-Id: <20230111180651.14394-3-dwmw2@infradead.org> Signed-off-by: Paolo Bonzini --- virt/kvm/kvm_main.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'virt') diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 13e88297f999..9c60384b5ae0 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3954,6 +3954,13 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id) } mutex_lock(&kvm->lock); + +#ifdef CONFIG_LOCKDEP + /* Ensure that lockdep knows vcpu->mutex is taken *inside* kvm->lock */ + mutex_lock(&vcpu->mutex); + mutex_unlock(&vcpu->mutex); +#endif + if (kvm_get_vcpu_by_id(kvm, id)) { r = -EEXIST; goto unlock_vcpu_destroy; -- cgit v1.2.3