Re: [Qemu-devel] [PATCH] implement moderation registers for e1000

[Luigi Rizzo]

On Fri, Feb 08, 2013 at 11:46:34AM +0100, Paolo Bonzini wrote:
> Il 08/02/2013 11:20, Luigi Rizzo ha scritto:
...
> > I am happy to make this default to off. But it would be good if you could
> > actually give it a try. Note that linux and FreeBSD (and presumably windows)
> > do use moderation by default so enabling the emulation of the
> > registers makes the guest OS behave differently (and closer to bare metal).
> > 
> > To test that the patch itself does not cause regression in the emulator
> > one should also turn off moderation in the guest (one of the tests i
> > have run).
> 
> I think making the default on is fine, but you need to add compatibility
> options to leave it off in older machine types (pc-1.4 and earlier).

I am unclear on what you mean by "older machine types" ?
The hardware (E1000_DEV_ID_82540EM) does have these registers,
and it is entirely up to the guest OS to use them or not.

cheers
luigi