Re: [PATCH v3 4/4] KVM: TDX: Enable Bus Lock VM exit

[Xiaoyao Li]

On 8/13/2026 6:58 AM, Edgecombe, Rick P wrote:
> On Wed, 2026-08-12 at 16:02 +0800, Xiaoyao Li wrote:
> > -	if (unlikely(READ_ONCE(to_kvm_tdx(vcpu->kvm)->wait_for_sept_zap)))
> > +	if (unlikely(READ_ONCE(to_kvm_tdx(vcpu->kvm)->wait_for_sept_zap))) {
> > +		vt->exit_reason.bus_lock_detected = 0;
> >   		return EXIT_FASTPATH_EXIT_HANDLED;
> > +	}
> >   
>
> This still feels hacky to me. It at least deserves a comment I think. If you
> spin another version.

I spent more time on this today and I find there is an existing issue. 
When the previous Exit Reason is EXIT_REASON_EXTERNAL_INTERRUPT, the 
early return here can go to the path due to the stale exit_reason.

kvm_x86_call(handle_exit_irqoff)(vcpu)
  vmx_handle_exit_irqoff()
    handle_external_interrupt_irqoff()

This makes the host process the external interrupt twice, and maybe more 
times if the wait_for_sept_zap remains longer.

I think we need an separate fix to set

	vt->exit_reasons.full = TDX_INVALID_EXIT_REASON;

so that if some patch is going to consume the stale Exit Reason, it can 
be caught by TDX_INVALID_EXIT_REASON.