Re: [RESEND PATCH 5/6] KVM: x86/VMX: add kvm_vmx_reinject_nmi_irq() for NMI/IRQ reinjection

Peter Zijlstra
2022-11-11T14:24:49Z

On Fri, Nov 11, 2022 at 01:48:26PM +0100, Paolo Bonzini wrote:
> On 11/11/22 13:19, Peter Zijlstra wrote:
> > On Fri, Nov 11, 2022 at 01:04:27PM +0100, Paolo Bonzini wrote:
> > > On Intel you can optionally make it hold onto IRQs, but NMIs are always
> > > eaten by the VMEXIT and have to be reinjected manually.
> >
> > That 'optionally' thing worries me -- as in, KVM is currently
> > opting-out?
>
> Yes, because "If the “process posted interrupts” VM-execution control is 1,
> the “acknowledge interrupt on exit” VM-exit control is 1" (SDM 26.2.1.1,
> checks on VM-Execution Control Fields). Ipse dixit. Posted interrupts are
> available and used on all processors since I think Ivy Bridge.

(imagine the non-coc compliant reaction here)

So instead of fixing it, they made it worse :-(

And now FRED is arguably making it worse again, and people wonder why I
hate virt...