From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:49528) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hFzp7-0005Bv-Mg for qemu-devel@nongnu.org; Mon, 15 Apr 2019 07:30:54 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hFzp6-0000df-Cl for qemu-devel@nongnu.org; Mon, 15 Apr 2019 07:30:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43900) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hFzp6-0000dA-3B for qemu-devel@nongnu.org; Mon, 15 Apr 2019 07:30:52 -0400 Date: Mon, 15 Apr 2019 12:30:46 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20190415113045.GI2852@work-vm> References: <20190411123911.GR3641@redhat.com> <226271554987011@iva6-8a76e93b6298.qloud-c.yandex.net> <243191555321803@vla1-1374b6242101.qloud-c.yandex.net> <20190415101101.GF5718@redhat.com> <251681555323421@vla1-1374b6242101.qloud-c.yandex.net> <20190415102520.GG5718@redhat.com> <259551555324396@vla1-1374b6242101.qloud-c.yandex.net> <20190415104725.GI5718@redhat.com> <20190415111511.GG2852@work-vm> <20190415111911.GK5718@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20190415111911.GK5718@redhat.com> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= Cc: Yury Kotov , "qemu-devel@nongnu.org" , "yc-core@yandex-team.ru" , Juan Quintela * Daniel P. Berrang=E9 (berrange@redhat.com) wrote: > On Mon, Apr 15, 2019 at 12:15:12PM +0100, Dr. David Alan Gilbert wrote: > > * Daniel P. Berrang=E9 (berrange@redhat.com) wrote: > > > On Mon, Apr 15, 2019 at 01:33:21PM +0300, Yury Kotov wrote: > > > > 15.04.2019, 13:25, "Daniel P. Berrang=E9" : > > > > > On Mon, Apr 15, 2019 at 01:17:06PM +0300, Yury Kotov wrote: > > > > >> =A015.04.2019, 13:11, "Daniel P. Berrang=E9" : > > > > >> =A0> On Mon, Apr 15, 2019 at 12:50:08PM +0300, Yury Kotov wrot= e: > > > > >> =A0>> =A0Hi, > > > > >> =A0>> > > > > >> =A0>> =A0Just to clarify. I see two possible solutions: > > > > >> =A0>> > > > > >> =A0>> =A01) Since the migration code doesn't receive fd, it is= n't responsible for > > > > >> =A0>> =A0closing it. So, it may be better to use migrate_fd_pa= ram for both > > > > >> =A0>> =A0incoming/outgoing and add dupping for migrate_fd_para= m. Thus, clients must > > > > >> =A0>> =A0close the fd themselves. But existing clients will ha= ve a leak. > > > > >> =A0> > > > > >> =A0> We can't break existing clients in this way as they are c= orrectly > > > > >> =A0> using the monitor with its current semantics. > > > > >> =A0> > > > > >> =A0>> =A02) If we don't duplicate fd, then at least we should = remove fd from > > > > >> =A0>> =A0the corresponding list. Therefore, the solution is to= fix qemu_close to find > > > > >> =A0>> =A0the list and remove fd from it. But qemu_close is cur= rently consistent with > > > > >> =A0>> =A0qemu_open (which opens/dups fd), so adding additional= logic might not be > > > > >> =A0>> =A0a very good idea. > > > > >> =A0> > > > > >> =A0> qemu_close is not appropriate place to deal with somethin= g speciifc > > > > >> =A0> to the montor. > > > > >> =A0> > > > > >> =A0>> =A0I don't see any other solution, but I might miss some= thing. > > > > >> =A0>> =A0What do you think? > > > > >> =A0> > > > > >> =A0> All callers of monitor_get_fd() will close() the FD they = get back. > > > > >> =A0> Thus monitor_get_fd() should remove it from the list when= it returns > > > > >> =A0> it, and we should add API docs to monitor_get_fd() to exp= lain this. > > > > >> =A0> > > > > >> =A0Ok, it sounds reasonable. But monitor_get_fd is only about = outgoing migration. > > > > >> =A0But what about the incoming migration? It doesn't use monit= or_get_fd but just > > > > >> =A0converts input string to int and use it as fd. > > > > > > > > > > The incoming migration expects the FD to be passed into QEMU by= the mgmt > > > > > app when it is exec'ing the QEMU binary. It doesn't interact wi= th the > > > > > monitor at all AFAIR. > > > > > > > > >=20 > > > > Oh, sorry. This use case is not obvious. We used add-fd to pass f= d for > > > > migrate-incoming and such way has described problems. > > >=20 > > > That's a bug in your usage of QEMU IMHO, as the incoming code is no= t > > > designed to use add-fd. > >=20 > > Hmm, that's true - although: > > a) It's very non-obvious > > b) Unfortunate, since it would go well with -incoming defer >=20 > Yeah I think this is a screw up on QMEU's part when introducing 'defer'= . >=20 > We should have mandated use of 'add-fd' when using 'defer', since FD > inheritance-over-execve() should only be used for command line args, > not monitor commands. >=20 > Not sure how to best fix this is QEMU though without breaking back > compat for apps using 'defer' already. We could add mon-fd: transports that has the same behaviour as now for outgoing, and for incoming uses the add-fd stash. Dave > Regards, > Daniel > --=20 > |: https://berrange.com -o- https://www.flickr.com/photos/dberr= ange :| > |: https://libvirt.org -o- https://fstop138.berrange= .com :| > |: https://entangle-photo.org -o- https://www.instagram.com/dberr= ange :| -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,T_HK_NAME_DR,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3B5BAC10F0E for ; Mon, 15 Apr 2019 11:31:50 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0906D20818 for ; Mon, 15 Apr 2019 11:31:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0906D20818 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([127.0.0.1]:48568 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hFzq1-0005VM-93 for qemu-devel@archiver.kernel.org; Mon, 15 Apr 2019 07:31:49 -0400 Received: from eggs.gnu.org ([209.51.188.92]:49528) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hFzp7-0005Bv-Mg for qemu-devel@nongnu.org; Mon, 15 Apr 2019 07:30:54 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hFzp6-0000df-Cl for qemu-devel@nongnu.org; Mon, 15 Apr 2019 07:30:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43900) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hFzp6-0000dA-3B for qemu-devel@nongnu.org; Mon, 15 Apr 2019 07:30:52 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 372573086201; Mon, 15 Apr 2019 11:30:51 +0000 (UTC) Received: from work-vm (ovpn-117-222.ams2.redhat.com [10.36.117.222]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 645A95D707; Mon, 15 Apr 2019 11:30:49 +0000 (UTC) Date: Mon, 15 Apr 2019 12:30:46 +0100 From: "Dr. David Alan Gilbert" To: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= Message-ID: <20190415113045.GI2852@work-vm> References: <20190411123911.GR3641@redhat.com> <226271554987011@iva6-8a76e93b6298.qloud-c.yandex.net> <243191555321803@vla1-1374b6242101.qloud-c.yandex.net> <20190415101101.GF5718@redhat.com> <251681555323421@vla1-1374b6242101.qloud-c.yandex.net> <20190415102520.GG5718@redhat.com> <259551555324396@vla1-1374b6242101.qloud-c.yandex.net> <20190415104725.GI5718@redhat.com> <20190415111511.GG2852@work-vm> <20190415111911.GK5718@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline In-Reply-To: <20190415111911.GK5718@redhat.com> User-Agent: Mutt/1.11.4 (2019-03-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.42]); Mon, 15 Apr 2019 11:30:51 +0000 (UTC) Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Yury Kotov , "qemu-devel@nongnu.org" , "yc-core@yandex-team.ru" , Juan Quintela Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Message-ID: <20190415113046.h3otAmCZCBOffF738maaUDIH3Wf-pt_mPOhnKf4l1UY@z> * Daniel P. Berrang=E9 (berrange@redhat.com) wrote: > On Mon, Apr 15, 2019 at 12:15:12PM +0100, Dr. David Alan Gilbert wrote: > > * Daniel P. Berrang=E9 (berrange@redhat.com) wrote: > > > On Mon, Apr 15, 2019 at 01:33:21PM +0300, Yury Kotov wrote: > > > > 15.04.2019, 13:25, "Daniel P. Berrang=E9" : > > > > > On Mon, Apr 15, 2019 at 01:17:06PM +0300, Yury Kotov wrote: > > > > >> =A015.04.2019, 13:11, "Daniel P. Berrang=E9" : > > > > >> =A0> On Mon, Apr 15, 2019 at 12:50:08PM +0300, Yury Kotov wrot= e: > > > > >> =A0>> =A0Hi, > > > > >> =A0>> > > > > >> =A0>> =A0Just to clarify. I see two possible solutions: > > > > >> =A0>> > > > > >> =A0>> =A01) Since the migration code doesn't receive fd, it is= n't responsible for > > > > >> =A0>> =A0closing it. So, it may be better to use migrate_fd_pa= ram for both > > > > >> =A0>> =A0incoming/outgoing and add dupping for migrate_fd_para= m. Thus, clients must > > > > >> =A0>> =A0close the fd themselves. But existing clients will ha= ve a leak. > > > > >> =A0> > > > > >> =A0> We can't break existing clients in this way as they are c= orrectly > > > > >> =A0> using the monitor with its current semantics. > > > > >> =A0> > > > > >> =A0>> =A02) If we don't duplicate fd, then at least we should = remove fd from > > > > >> =A0>> =A0the corresponding list. Therefore, the solution is to= fix qemu_close to find > > > > >> =A0>> =A0the list and remove fd from it. But qemu_close is cur= rently consistent with > > > > >> =A0>> =A0qemu_open (which opens/dups fd), so adding additional= logic might not be > > > > >> =A0>> =A0a very good idea. > > > > >> =A0> > > > > >> =A0> qemu_close is not appropriate place to deal with somethin= g speciifc > > > > >> =A0> to the montor. > > > > >> =A0> > > > > >> =A0>> =A0I don't see any other solution, but I might miss some= thing. > > > > >> =A0>> =A0What do you think? > > > > >> =A0> > > > > >> =A0> All callers of monitor_get_fd() will close() the FD they = get back. > > > > >> =A0> Thus monitor_get_fd() should remove it from the list when= it returns > > > > >> =A0> it, and we should add API docs to monitor_get_fd() to exp= lain this. > > > > >> =A0> > > > > >> =A0Ok, it sounds reasonable. But monitor_get_fd is only about = outgoing migration. > > > > >> =A0But what about the incoming migration? It doesn't use monit= or_get_fd but just > > > > >> =A0converts input string to int and use it as fd. > > > > > > > > > > The incoming migration expects the FD to be passed into QEMU by= the mgmt > > > > > app when it is exec'ing the QEMU binary. It doesn't interact wi= th the > > > > > monitor at all AFAIR. > > > > > > > > >=20 > > > > Oh, sorry. This use case is not obvious. We used add-fd to pass f= d for > > > > migrate-incoming and such way has described problems. > > >=20 > > > That's a bug in your usage of QEMU IMHO, as the incoming code is no= t > > > designed to use add-fd. > >=20 > > Hmm, that's true - although: > > a) It's very non-obvious > > b) Unfortunate, since it would go well with -incoming defer >=20 > Yeah I think this is a screw up on QMEU's part when introducing 'defer'= . >=20 > We should have mandated use of 'add-fd' when using 'defer', since FD > inheritance-over-execve() should only be used for command line args, > not monitor commands. >=20 > Not sure how to best fix this is QEMU though without breaking back > compat for apps using 'defer' already. We could add mon-fd: transports that has the same behaviour as now for outgoing, and for incoming uses the add-fd stash. Dave > Regards, > Daniel > --=20 > |: https://berrange.com -o- https://www.flickr.com/photos/dberr= ange :| > |: https://libvirt.org -o- https://fstop138.berrange= .com :| > |: https://entangle-photo.org -o- https://www.instagram.com/dberr= ange :| -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK