Re: [PATCH v7 02/10] x86/fred: Pass event data to the NMI entry point from KVM

[H. Peter Anvin]

On 2025-06-19 15:57, Sohil Mehta wrote:
> On 6/19/2025 3:45 PM, Xin Li wrote:
> > On 6/19/2025 3:15 PM, Sohil Mehta wrote:
> > > I want to say that the event data for IRQ has to be zero until the
> > > architecture changes — Similar to the /* Reserved, must be 0 */ comment
> > > in asm_fred_entry_from_kvm().
> >
> > FRED spec says:
> >
> > For any other event, the event data are not currently defined and will
> > be zero until they are.
> >
> > So "Event data not defined for IRQ thus 0."
>
> I am fine with this. Not *defined* removes the ambiguity.

So I was thinking about this, and wonder: how expensive is it to get the 
event data exit information out of VMX? If it is not very expensive, it 
would arguably be a good thing to future-proof by fetching that 
information, even if it is currently always zero.

	-hpa