From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:46773) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hFza3-0000ok-Fj for qemu-devel@nongnu.org; Mon, 15 Apr 2019 07:15:20 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hFza2-0008I8-AM for qemu-devel@nongnu.org; Mon, 15 Apr 2019 07:15:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46850) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hFza2-0008Hv-12 for qemu-devel@nongnu.org; Mon, 15 Apr 2019 07:15:18 -0400 Date: Mon, 15 Apr 2019 12:15:12 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20190415111511.GG2852@work-vm> References: <20190411120421.GP3641@redhat.com> <219131554985898@iva6-8a76e93b6298.qloud-c.yandex.net> <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> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20190415104725.GI5718@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 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 wrote: > > >> =A0>> =A0Hi, > > >> =A0>> > > >> =A0>> =A0Just to clarify. I see two possible solutions: > > >> =A0>> > > >> =A0>> =A01) Since the migration code doesn't receive fd, it isn't = responsible for > > >> =A0>> =A0closing it. So, it may be better to use migrate_fd_param = for both > > >> =A0>> =A0incoming/outgoing and add dupping for migrate_fd_param. T= hus, clients must > > >> =A0>> =A0close the fd themselves. But existing clients will have a= leak. > > >> =A0> > > >> =A0> We can't break existing clients in this way as they are corre= ctly > > >> =A0> using the monitor with its current semantics. > > >> =A0> > > >> =A0>> =A02) If we don't duplicate fd, then at least we should remo= ve 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 current= ly consistent with > > >> =A0>> =A0qemu_open (which opens/dups fd), so adding additional log= ic might not be > > >> =A0>> =A0a very good idea. > > >> =A0> > > >> =A0> qemu_close is not appropriate place to deal with something sp= eciifc > > >> =A0> to the montor. > > >> =A0> > > >> =A0>> =A0I don't see any other solution, but I might miss somethin= g. > > >> =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 explain= this. > > >> =A0> > > >> =A0Ok, it sounds reasonable. But monitor_get_fd is only about outg= oing migration. > > >> =A0But what about the incoming migration? It doesn't use monitor_g= et_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 with t= he > > > monitor at all AFAIR. > > > > >=20 > > Oh, sorry. This use case is not obvious. We used add-fd to pass fd fo= r > > migrate-incoming and such way has described problems. >=20 > That's a bug in your usage of QEMU IMHO, as the incoming code is not > designed to use add-fd. Hmm, that's true - although: a) It's very non-obvious b) Unfortunate, since it would go well with -incoming defer 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 990A9C10F0E for ; Mon, 15 Apr 2019 11:16:11 +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 6A8092073F for ; Mon, 15 Apr 2019 11:16:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6A8092073F 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]:48419 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hFzas-0001Dp-J7 for qemu-devel@archiver.kernel.org; Mon, 15 Apr 2019 07:16:10 -0400 Received: from eggs.gnu.org ([209.51.188.92]:46773) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hFza3-0000ok-Fj for qemu-devel@nongnu.org; Mon, 15 Apr 2019 07:15:20 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hFza2-0008I8-AM for qemu-devel@nongnu.org; Mon, 15 Apr 2019 07:15:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46850) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hFza2-0008Hv-12 for qemu-devel@nongnu.org; Mon, 15 Apr 2019 07:15:18 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 77B8730832C9; Mon, 15 Apr 2019 11:15:16 +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 D4BB219C4F; Mon, 15 Apr 2019 11:15:14 +0000 (UTC) Date: Mon, 15 Apr 2019 12:15:12 +0100 From: "Dr. David Alan Gilbert" To: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= Message-ID: <20190415111511.GG2852@work-vm> References: <20190411120421.GP3641@redhat.com> <219131554985898@iva6-8a76e93b6298.qloud-c.yandex.net> <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> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline In-Reply-To: <20190415104725.GI5718@redhat.com> User-Agent: Mutt/1.11.4 (2019-03-13) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.44]); Mon, 15 Apr 2019 11:15:16 +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: <20190415111512.8kGDSA4DF8fN8iCpZ6UoeL3-LfHy4ROwAK3u6r7NmLY@z> * 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 wrote: > > >> =A0>> =A0Hi, > > >> =A0>> > > >> =A0>> =A0Just to clarify. I see two possible solutions: > > >> =A0>> > > >> =A0>> =A01) Since the migration code doesn't receive fd, it isn't = responsible for > > >> =A0>> =A0closing it. So, it may be better to use migrate_fd_param = for both > > >> =A0>> =A0incoming/outgoing and add dupping for migrate_fd_param. T= hus, clients must > > >> =A0>> =A0close the fd themselves. But existing clients will have a= leak. > > >> =A0> > > >> =A0> We can't break existing clients in this way as they are corre= ctly > > >> =A0> using the monitor with its current semantics. > > >> =A0> > > >> =A0>> =A02) If we don't duplicate fd, then at least we should remo= ve 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 current= ly consistent with > > >> =A0>> =A0qemu_open (which opens/dups fd), so adding additional log= ic might not be > > >> =A0>> =A0a very good idea. > > >> =A0> > > >> =A0> qemu_close is not appropriate place to deal with something sp= eciifc > > >> =A0> to the montor. > > >> =A0> > > >> =A0>> =A0I don't see any other solution, but I might miss somethin= g. > > >> =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 explain= this. > > >> =A0> > > >> =A0Ok, it sounds reasonable. But monitor_get_fd is only about outg= oing migration. > > >> =A0But what about the incoming migration? It doesn't use monitor_g= et_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 with t= he > > > monitor at all AFAIR. > > > > >=20 > > Oh, sorry. This use case is not obvious. We used add-fd to pass fd fo= r > > migrate-incoming and such way has described problems. >=20 > That's a bug in your usage of QEMU IMHO, as the incoming code is not > designed to use add-fd. Hmm, that's true - although: a) It's very non-obvious b) Unfortunate, since it would go well with -incoming defer 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