Commit 605c7130 authored by Peter Xu's avatar Peter Xu Committed by Paolo Bonzini
Browse files

KVM: Introduce kvm_get_kvm_safe() 



Introduce this safe version of kvm_get_kvm() so that it can be called even
during vm destruction.  Use it in kvm_debugfs_open() and remove the verbose
comment.  Prepare to be used elsewhere.

Signed-off-by: default avatarPeter Xu <peterx@redhat.com>
Message-Id: <20210625153214.43106-3-peterx@redhat.com>
[Preserve the comment in kvm_debugfs_open. - Paolo]
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 1694caef

include/linux/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -755,6 +755,7 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align, 
void kvm_exit(void);



void kvm_get_kvm(struct kvm *kvm);

bool kvm_get_kvm_safe(struct kvm *kvm);

void kvm_put_kvm(struct kvm *kvm);

bool file_is_kvm(struct file *file);

void kvm_put_kvm_no_destroy(struct kvm *kvm);

virt/kvm/kvm_main.c

+15 −5
Original line number Diff line number Diff line
@@ -1120,6 +1120,16 @@ void kvm_get_kvm(struct kvm *kvm) 
}

EXPORT_SYMBOL_GPL(kvm_get_kvm);



/*

 * Make sure the vm is not during destruction, which is a safe version of

 * kvm_get_kvm().  Return true if kvm referenced successfully, false otherwise.

 */

bool kvm_get_kvm_safe(struct kvm *kvm)

{

	return refcount_inc_not_zero(&kvm->users_count);

}

EXPORT_SYMBOL_GPL(kvm_get_kvm_safe);



void kvm_put_kvm(struct kvm *kvm)

{

	if (refcount_dec_and_test(&kvm->users_count))
@@ -4969,12 +4979,12 @@ static int kvm_debugfs_open(struct inode *inode, struct file *file, 
	struct kvm_stat_data *stat_data = (struct kvm_stat_data *)

					  inode->i_private;



	/* The debugfs files are a reference to the kvm struct which

	 * is still valid when kvm_destroy_vm is called.

	 * To avoid the race between open and the removal of the debugfs

	 * directory we test against the users count.

	/*

	 * The debugfs files are a reference to the kvm struct which

        * is still valid when kvm_destroy_vm is called.  kvm_get_kvm_safe

        * avoids the race between open and the removal of the debugfs directory.

	 */

	if (!refcount_inc_not_zero(&stat_data->kvm->users_count))

	if (!kvm_get_kvm_safe(stat_data->kvm))

		return -ENOENT;



	if (simple_attr_open(inode, file, get,