Commit 2b012812 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: Register /dev/kvm as the _very_ last thing during initialization 



Register /dev/kvm, i.e. expose KVM to userspace, only after all other
setup has completed.  Once /dev/kvm is exposed, userspace can start
invoking KVM ioctls, creating VMs, etc...  If userspace creates a VM
before KVM is done with its configuration, bad things may happen, e.g.
KVM will fail to properly migrate vCPU state if a VM is created before
KVM has registered preemption notifiers.

Cc: stable@vger.kernel.org
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20221130230934.1014142-2-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent fc471e83

virt/kvm/kvm_main.c

+22 −9
Original line number Diff line number Diff line
@@ -5988,12 +5988,6 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align, 


	kvm_chardev_ops.owner = module;



	r = misc_register(&kvm_dev);

	if (r) {

		pr_err("kvm: misc device register failed\n");

		goto out_unreg;

	}



	register_syscore_ops(&kvm_syscore_ops);



	kvm_preempt_ops.sched_in = kvm_sched_in;
@@ -6002,11 +5996,24 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align, 
	kvm_init_debug();



	r = kvm_vfio_ops_init();

	WARN_ON(r);

	if (WARN_ON_ONCE(r))

		goto err_vfio;



	/*

	 * Registration _must_ be the very last thing done, as this exposes

	 * /dev/kvm to userspace, i.e. all infrastructure must be setup!

	 */

	r = misc_register(&kvm_dev);

	if (r) {

		pr_err("kvm: misc device register failed\n");

		goto err_register;

	}



	return 0;



out_unreg:

err_register:

	kvm_vfio_ops_exit();

err_vfio:

	kvm_async_pf_deinit();

out_free_4:

	for_each_possible_cpu(cpu)
@@ -6032,8 +6039,14 @@ void kvm_exit(void) 
{

	int cpu;



	debugfs_remove_recursive(kvm_debugfs_dir);

	/*

	 * Note, unregistering /dev/kvm doesn't strictly need to come first,

	 * fops_get(), a.k.a. try_module_get(), prevents acquiring references

	 * to KVM while the module is being stopped.

	 */

	misc_deregister(&kvm_dev);



	debugfs_remove_recursive(kvm_debugfs_dir);

	for_each_possible_cpu(cpu)

		free_cpumask_var(per_cpu(cpu_kick_mask, cpu));

	kmem_cache_destroy(kvm_vcpu_cache);