Re: QEMU PIC indirection patch for in-kernel APIC work

Rusty Russell
2007-04-09T02:50:18Z

On Sun, 2007-04-08 at 08:36 +0300, Avi Kivity wrote:
> Rusty Russell wrote:
> > Hi Avi,
> >
> > I don't think you've thought about this very hard. The receive copy is
> > completely independent with whether the packet is going to the guest via
> > a kernel driver or via userspace, so not relevant.
> >
>
> A packet received in the kernel cannot be made available to userspace in
> a safe manner without a copy, as it will not be aligned with page
> boundaries, so userspace cannot examine the packet until after one copy
> has occured.

Hi Avi!

I'm a little puzzled by your response. Hmm...

lguest's userspace network frontend does exactly as many copies as
Ingo's in-host-kernel code. One from the Guest, one to the Guest.

Does that clarify?
Rusty.