Re: [PATCH v2 1/2] x86/kvm/vmx: Move IRQ/NMI dispatch from KVM into x86 core

[Peter Zijlstra]

On Fri, May 08, 2026 at 02:09:09PM +0800, Binbin Wu wrote:
> On 5/2/2026 4:37 AM, Peter Zijlstra wrote:

> > +noinstr void x86_entry_from_kvm(unsigned int event_type, unsigned int vector)
> > +{
> > +	if (event_type == EVENT_TYPE_EXTINT) {
> > +#ifdef CONFIG_X86_64
> > +		/*
> > +		 * Use FRED dispatch, even when running IDT. The dispatch
> > +		 * tables are kept in sync between FRED and IDT, and the FRED
> > +		 * dispatch works well with CFI.
> > +		 */
> > +		fred_entry_from_kvm(event_type, vector);
> > +#else
> > +		idt_entry_from_kvm(vector);
> > +#endif
> > +		return;
> > +	}
> > +
> > +	WARN_ON_ONCE(event_type != EVENT_TYPE_NMI);
> 
> Not sure if it's OK to use WARN_ON_ONCE() here.
> If the warning is triggered, it could unblock NMI due to handling of #UD.

If that ever triggers you've got bigger problems.

> > --- a/arch/x86/include/asm/desc.h
> > +++ b/arch/x86/include/asm/desc.h
> > @@ -438,6 +438,10 @@ extern void idt_setup_traps(void);
> >  extern void idt_setup_apic_and_irq_gates(void);
> >  extern bool idt_is_f00f_address(unsigned long address);
> >  
> > +extern void idt_do_interrupt_irqoff(unsigned int vector);
> 
> In idt_entry_from_kvm() below, gate_offset() returns 'unsigned long', but here
> it uses 'unsigned int'. It's not safe since there is no guarantee that the
> address is within 32 bits for x86_64.
> 

Right you are, 'unsigned long address' it is.