KVM: x86: Treat a vCPU as unreachable if its index is invalid

In the "vCPU locked or unreachable" lockdep assertion, treat a vCPU as
unreachable if its index is invalid, i.e. if the vCPU is in the process of
being created.  Until the vCPU is inserted into the array of vCPUs, the
only way to get at the vCPU is via kvm_vm_ioctl_create_vcpu().  Note, the
actual index is set _before_ adding the vCPU to the array, i.e. there's no
risk of a false negative on the lockdep assertion.

Reviewed-by: Philippe Mathieu-Daudé <philmd@oss.qualcomm.com>
Link: https://patch.msgid.link/20260630225619.511632-10-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index b10814f99a50..0bdfa3699352 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -992,6 +992,7 @@ static inline struct kvm_io_bus *kvm_get_bus(struct kvm *kvm, enum kvm_bus idx)
 static inline void kvm_lockdep_assert_vcpu_is_locked_or_unreachable(struct kvm_vcpu *vcpu)
 {
 	lockdep_assert_once(lockdep_is_held(&vcpu->mutex) ||
+			    vcpu->vcpu_idx < 0 ||
 			    !refcount_read(&vcpu->kvm->users_count));
 }