Re: [PATCH] kvm: x86: disable KVM_FAST_MMIO_BUS

[Paolo Bonzini]

> We actually know what to expect (a write) so we could maybe
> optimize this some more with a dedicated function just for this.

We don't know the addressing mode, the size or the source (immediate
vs. register), so no.

KVM is already doing a single translation and read no matter how long
the instruction (unless it cross page boundaries).

Paolo

> > 
> > However, the eventfd is written before decoding, while full emulation
> > would write it after. So while VCPU thread latency is worse compared to
> > skip_emulated_instruction, latency to the iothread remains small.
> > 
> > Paolo
>