From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:50662) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TQaw2-0005UO-Eg for qemu-devel@nongnu.org; Tue, 23 Oct 2012 05:38:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TQavw-0007hT-KP for qemu-devel@nongnu.org; Tue, 23 Oct 2012 05:38:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:2642) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TQavw-0007h8-Be for qemu-devel@nongnu.org; Tue, 23 Oct 2012 05:38:00 -0400 Message-ID: <5086656A.6060603@redhat.com> Date: Tue, 23 Oct 2012 11:37:46 +0200 From: Avi Kivity MIME-Version: 1.0 References: <1350897839-29593-1-git-send-email-pingfank@linux.vnet.ibm.com> <1350897839-29593-14-git-send-email-pingfank@linux.vnet.ibm.com> <50852299.8090109@redhat.com> <50865E3F.4010809@siemens.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [patch v4 13/16] e1000: add busy flag to anti broken device state List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: liu ping fan Cc: Liu Ping Fan , Jan Kiszka , Marcelo Tosatti , "qemu-devel@nongnu.org" , Anthony Liguori , Stefan Hajnoczi , Paolo Bonzini On 10/23/2012 11:32 AM, liu ping fan wrote: > On Tue, Oct 23, 2012 at 5:07 PM, Jan Kiszka wrote: >> On 2012-10-23 07:52, liu ping fan wrote: >>> On Mon, Oct 22, 2012 at 6:40 PM, Avi Kivity wrote: >>>> On 10/22/2012 11:23 AM, Liu Ping Fan wrote: >>>>> The broken device state is caused by releasing local lock before acquiring >>>>> big lock. To fix this issue, we have two choice: >>>>> 1.use busy flag to protect the state >>>>> The drawback is that we will introduce independent busy flag for each >>>>> independent device's logic unit. >>>>> 2.reload the device's state >>>>> The drawback is if the call chain is too deep, the action to reload will >>>>> touch each layer. Also the reloading means to recaculate the intermediate >>>>> result based on device's regs. >>>>> >>>>> This patch adopt the solution 1 to fix the issue. >>>> >>>> Doesn't the nested mmio patch detect this? >>>> >>> It will only record and fix the issue on one thread. But guest can >>> touch the emulated device on muti-threads. >> >> Sorry, what does that mean? A second VCPU accessing the device will >> simply be ignored when it races with another VCPU? Specifically >> > Yes, just ignored. For device which support many logic in parallel, > it should use independent busy flag for each logic We don't actually know that e1000 doesn't. Why won't writing into different registers in parallel work? -- error compiling committee.c: too many arguments to function