From mboxrd@z Thu Jan 1 00:00:00 1970 From: konrad wilk Subject: Re: [PATCH] xen/pci: Deal with toolstack missing an 'XenbusStateClosing'. Date: Tue, 11 Jun 2013 12:08:23 -0400 Message-ID: <51B74B77.1000806@oracle.com> References: <20130610202456.GA17822@phenom.dumpdata.com> <1370898399-20968-1-git-send-email-konrad.wilk@oracle.com> <1370898399-20968-2-git-send-email-konrad.wilk@oracle.com> <51B743EA.5020800@eu.citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <51B743EA.5020800@eu.citrix.com> Sender: stable-owner@vger.kernel.org To: George Dunlap Cc: xen-devel@lists.xensource.com, linux-kernel@vger.kernel.org, Bjorn Helgaas , linux-pci@vger.kernel.org, stable@vger.kernel.org List-Id: xen-devel@lists.xenproject.org On 6/11/2013 11:36 AM, George Dunlap wrote: > On 06/10/2013 10:06 PM, Konrad Rzeszutek Wilk wrote: >> There are two tool-stack that can instruct the Xen PCI frontend >> and backend to change states: 'xm' (Python code with a daemon), >> and 'xl' (C library - does not keep state changes). >> >> With the 'xm', the path to disconnect a PCI device (xm pci-detach >> )is: >> >> 4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)-> >> 4(Connected)->5(Closing*). >> >> The * is for states that the tool-stack sets. For 'xl', it is similar: >> >> 4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)-> 4(Connected) >> >> Both of them also tear down the XenBus structure, so the backend >> state ends up going in the 3(Initialised) and calls >> pcifront_xenbus_remove. > > So I looked a little bit into this; there are actually two different > states that happen as part of this handshake. In order to disonnect a > *device*, xl signals using the *bus* state, like this: > * Wait for the *bus* to be in state 4(Connected) > * Set the *device* state to 5(Closing) > * Set the *bus* state to 7(Reconfiguring) > * Wait for the *bus* state to return to 4(Connected) > > So are all of these states you see the *bus* state? And why would you > disconnect the whole pci bus if you're only removing one device? Correct. The stats I enumerated are *bus* states. Not per-device states. I presume (and I hadn't checked xm) that Xend has some logic to only disconnect the bus if all of the PCI devices have been disconnected. In 'xl' it does not do that. The testing I did was just with one PCI device. > > -George