From mboxrd@z Thu Jan  1 00:00:00 1970
From: Charles Duffy <Charles_Duffy@messageone.com>
Subject: Re: e1000 PXE breakage bisected down in kvm-userspace
Date: Mon, 04 Aug 2008 20:07:03 -0500
Message-ID: <g78941$n6t$1@ger.gmane.org>
References: <g77qp3$frj$1@ger.gmane.org> <4897706A.8010206@codemonkey.ws> <g77rm6$ils$1@ger.gmane.org> <489777F9.1080404@codemonkey.ws>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
To: kvm@vger.kernel.org
Return-path: <kvm-owner@vger.kernel.org>
Received: from main.gmane.org ([80.91.229.2]:45859 "EHLO ciao.gmane.org"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1761575AbYHEBH0 (ORCPT <rfc822;kvm@vger.kernel.org>);
	Mon, 4 Aug 2008 21:07:26 -0400
Received: from list by ciao.gmane.org with local (Exim 4.43)
	id 1KQB1G-0007hz-8q
	for kvm@vger.kernel.org; Tue, 05 Aug 2008 01:07:22 +0000
Received: from rrcs-71-41-149-67.sw.biz.rr.com ([71.41.149.67])
        by main.gmane.org with esmtp (Gmexim 0.1 (Debian))
        id 1AlnuQ-0007hv-00
        for <kvm@vger.kernel.org>; Tue, 05 Aug 2008 01:07:22 +0000
Received: from Charles_Duffy by rrcs-71-41-149-67.sw.biz.rr.com with local (Gmexim 0.1 (Debian))
        id 1AlnuQ-0007hv-00
        for <kvm@vger.kernel.org>; Tue, 05 Aug 2008 01:07:22 +0000
In-Reply-To: <489777F9.1080404@codemonkey.ws>
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

Anthony Liguori wrote:
> diff --git a/qemu/hw/e1000.c b/qemu/hw/e1000.c
> index 1be69ec..6a07b0c 100644
> --- a/qemu/hw/e1000.c
> +++ b/qemu/hw/e1000.c
> @@ -521,8 +521,8 @@ e1000_can_receive(void *opaque)
> {
>     E1000State *s = opaque;
> 
> -    return ((s->mac_reg[RCTL] & E1000_RCTL_EN) &&
> -           s->mac_reg[RDH] != s->mac_reg[RDT]);
> +    return (!(s->mac_reg[RCTL] & E1000_RCTL_EN) ||
> +            s->mac_reg[RDH] != s->mac_reg[RDT]);
> }

Having e1000_can_receive return true only if s->mac_reg[RDH] != 
s->mac_reg[RDT] means that the logic in e1000_receive() which sets the 
receive overflow flag is never reached.

I think it may be more correct to check only for s->mac_reg[RCTL] & 
E1000_RCTL_EN.