From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nivedita Singhvi Subject: Re: qemu pcnet emulation problems. Date: Tue, 21 Mar 2006 17:36:54 -0800 Message-ID: <4420AA36.4020004@us.ibm.com> References: <20060322010235.GA16108@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20060322010235.GA16108@us.ibm.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Don Fry Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org Don Fry wrote: > There are/may be several other bugs with the qemu pcnet emulation. I do Not sure if Don mentioned this earlier, but for the benefit of those who might need the context, please see Xen Bugzilla #574/#575. > not know if there is any other serialization outside of this code, but if > both a transmit and a receive operation were to be performed at the same > time on different cpus, since the same buffer is used for both transmit > and receive, that would also cause data corruption. > > Does anyone else know how this is prevented, or is this another source > of corruption? > > Another thing I noticed, that will reduce throughput if corrected, is > that the wrong bit is being examined in the receive path, to determine > if mac level crc should be computed. Right now, the wrong bit is being > checked and no mac level crc is being calculated. If the right bit were > looked at, mac level crc would need to be computed, slowing down the > transfers. However, since no driver cares about the crc right now, > since neither Linux or XP complain, could the code to compute the crc be > deleted? Maybe just comment that the crc should be computed. > > Any recommendations? I'd really like to continue to avoid the CRC computation between domains, but intentionally, this time, in a clean way :). thanks, Nivedita