From: Mike Larkin <mlarkin@nested.page>
Subject: Re: [0/5] vmd: generate and expose ACPI tables to the guest via fw_cfg
To: Miguel Landaeta <miguel@miguel.cc>
Cc: tech@openbsd.org
Date: Tue, 16 Jun 2026 09:00:39 -0700

On Tue, Jun 16, 2026 at 10:21:34AM +0100, Miguel Landaeta wrote:
> On Tue 16 Jun 2026 at 00:42, Mike Larkin <mlarkin@nested.page> wrote:
>
> >
> > how do you deliver IPIs without a lapic?
>
>
> I haven’t emulated fully a LAPIC yet only a few bits. I guess for this PoC
> I found out that I don’t need one yet but my approach could be wrong, of
> course.
>
> The guest sends IPIs by writing the x2APIC ICR MSR (0x830). That’s a wrmsr,
> so it traps as an MSR exit rather than hitting a LAPIC register page. vmm
> decodes the delivery mode, destination and vector and forwards a synthetic
> exit to vmd, which injects the vector on the target vcpu’s next entry via
> the VMX entry-interruption field, similar to how it’s done for i8259 PIC
> vectors.
>
> So delivery is hardware event injection, not an APIC, I haven’t
> emulated/modelled APIC register file (IRR/ISR/TPR/EOI).
>
> >

that's a reasonable first step approach. let me take a look at what you've
got in that diff already :)