From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:38135) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UDufy-0002As-Nu for qemu-devel@nongnu.org; Fri, 08 Mar 2013 05:37:27 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UDufx-0001NU-2t for qemu-devel@nongnu.org; Fri, 08 Mar 2013 05:37:22 -0500 Received: from mx1.redhat.com ([209.132.183.28]:5378) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UDufw-0001NI-RC for qemu-devel@nongnu.org; Fri, 08 Mar 2013 05:37:20 -0500 Message-ID: <5139BF54.8000000@redhat.com> Date: Fri, 08 Mar 2013 18:37:08 +0800 From: Osier Yang MIME-Version: 1.0 References: <20130307100740.GB5302@redhat.com> <5138921D.5050604@suse.de> <87ehfrcn60.fsf@blackfin.pond.sub.org> <20130307163540.GB29071@redhat.com> <87k3pj3yzh.fsf@blackfin.pond.sub.org> <20130307181229.GB30633@redhat.com> <5138E3CD.8090105@suse.de> <20130307191549.GA12543@redhat.com> <51398EA3.5030004@redhat.com> <87boaujmvk.fsf@blackfin.pond.sub.org> <20130308092542.GG326424@orkuz.home> In-Reply-To: <20130308092542.GG326424@orkuz.home> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH] qdev: DEVICE_DELETED event List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster , Kevin Wolf , Anthony Liguori , Eduardo Habkost , "Michael S. Tsirkin" , "libvir-list@redhat.com" , Stefan Hajnoczi , qemu-devel@nongnu.org, Luiz Capitulino , Gerd Hoffmann , laine@redhat.com, Paolo Bonzini , =?UTF-8?B?QW5kcmVh?= =?UTF-8?B?cyBGw6RyYmVy?= On 2013=E5=B9=B403=E6=9C=8808=E6=97=A5 17:25, Jiri Denemark wrote: > On Fri, Mar 08, 2013 at 09:50:55 +0100, Markus Armbruster wrote: >> Osier Yang writes: >> >>> I'm wondering if it could be long time to wait for the device_del >>> completes (AFAIK from previous bugs, it can be, though it should be >>> fine for most of the cases). If it's too long, it will be a problem >>> for management, because it looks like hanging. We can have a timeout >>> for the device_del in libvirt, but the problem is the device_del >>> can be still in progress by qemu, which could cause the inconsistency. >>> Unless qemu has some command to cancel the device_del. >> >> I'm afraid cancelling isn't possible, at least not for PCI. > > I don't think we need anything like that. We just need the device > deletion API to return immediately without actually removing stuff from > domain definition (unless the device was really removed fast enough, > e.g., USB devices are removed before device_del returns) and then remov= e > the device from domain definition when we get the event from QEMU or > when libvirtd reconnects to a domain and sees a particular device is no > longer present. After all, devices may be removed even if we didn't ask > for it (when the removal is initiated by a guest OS). And we should als= o > provide similar event for higher level apps. Removing the device from domain config unless we get the event from qemu or find the device disappeared by polling makes sense. That's the mainly reason for we want the event and polling actually. But the problem is our APIs don't want to have long time hanging. If we don't change the APIs and return quickly just like what we do currently, it's confused for user, because when he wants to attach the device again while the device_del is still in progress, he will get the error like "Device ID *** is in used", however, our detaching APIs return success prior to that. I.E, if device_del needs long time to complete in some cases? can we live with it? Osier