KVM: SEV: Mark nested locking of kvm->lock

Both source and dest vms' kvm->locks are held in sev_lock_two_vms.
Mark one with a different subtype to avoid false positives from lockdep.

Fixes: c9d61dc (KVM: SEV: accept signals in sev_lock_two_vms)
Reported-by: Yiru Xu <[email protected]>
Tested-by: Jinrong Liang <[email protected]>
Signed-off-by: Wanpeng Li <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>

Author: Wanpeng Li

arch/x86/kvm/svm/sev.c

@@ -1565,7 +1565,7 @@ static int sev_lock_two_vms(struct kvm *dst_kvm, struct kvm *src_kvm)
 	r = -EINTR;
 	if (mutex_lock_killable(&dst_kvm->lock))
 		goto release_src;
-	if (mutex_lock_killable(&src_kvm->lock))
+	if (mutex_lock_killable_nested(&src_kvm->lock, SINGLE_DEPTH_NESTING))
 		goto unlock_dst;
 	return 0;