From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:51086) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hH9VN-0006Dn-1V for qemu-devel@nongnu.org; Thu, 18 Apr 2019 12:03:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hH9VL-00033R-Cl for qemu-devel@nongnu.org; Thu, 18 Apr 2019 12:03:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53220) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hH9VL-00032r-4b for qemu-devel@nongnu.org; Thu, 18 Apr 2019 12:03:15 -0400 Date: Thu, 18 Apr 2019 17:03:00 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20190418160300.GI2984@work-vm> References: <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> <20190415113045.GI2852@work-vm> <612681555412465@iva6-8a76e93b6298.qloud-c.yandex.net> <20190418141956.GF2984@work-vm> <1285061555601789@iva6-8a76e93b6298.qloud-c.yandex.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <1285061555601789@iva6-8a76e93b6298.qloud-c.yandex.net> 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: Yury Kotov Cc: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , "qemu-devel@nongnu.org" , "yc-core@yandex-team.ru" , Juan Quintela * Yury Kotov (yury-kotov@yandex-team.ru) wrote: > 18.04.2019, 17:20, "Dr. David Alan Gilbert" : > > * Yury Kotov (yury-kotov@yandex-team.ru) wrote: > >> =A015.04.2019, 14:30, "Dr. David Alan Gilbert" = : > >> =A0> * Daniel P. Berrang=E9 (berrange@redhat.com) wrote: > >> =A0>> =A0On Mon, Apr 15, 2019 at 12:15:12PM +0100, Dr. David Alan Gi= lbert wrote: > >> =A0>> =A0> * Daniel P. Berrang=E9 (berrange@redhat.com) wrote: > >> =A0>> =A0> > On Mon, Apr 15, 2019 at 01:33:21PM +0300, Yury Kotov wr= ote: > >> =A0>> =A0> > > 15.04.2019, 13:25, "Daniel P. Berrang=E9" : > >> =A0>> =A0> > > > On Mon, Apr 15, 2019 at 01:17:06PM +0300, Yury Koto= v wrote: > >> =A0>> =A0> > > >> =A015.04.2019, 13:11, "Daniel P. Berrang=E9" : > >> =A0>> =A0> > > >> =A0> On Mon, Apr 15, 2019 at 12:50:08PM +0300, Yur= y Kotov wrote: > >> =A0>> =A0> > > >> =A0>> =A0Hi, > >> =A0>> =A0> > > >> =A0>> > >> =A0>> =A0> > > >> =A0>> =A0Just to clarify. I see two possible solut= ions: > >> =A0>> =A0> > > >> =A0>> > >> =A0>> =A0> > > >> =A0>> =A01) Since the migration code doesn't recei= ve fd, it isn't responsible for > >> =A0>> =A0> > > >> =A0>> =A0closing it. So, it may be better to use m= igrate_fd_param for both > >> =A0>> =A0> > > >> =A0>> =A0incoming/outgoing and add dupping for mig= rate_fd_param. Thus, clients must > >> =A0>> =A0> > > >> =A0>> =A0close the fd themselves. But existing cli= ents will have a leak. > >> =A0>> =A0> > > >> =A0> > >> =A0>> =A0> > > >> =A0> We can't break existing clients in this way a= s they are correctly > >> =A0>> =A0> > > >> =A0> using the monitor with its current semantics. > >> =A0>> =A0> > > >> =A0> > >> =A0>> =A0> > > >> =A0>> =A02) If we don't duplicate fd, then at leas= t we should remove fd from > >> =A0>> =A0> > > >> =A0>> =A0the corresponding list. Therefore, the so= lution is to fix qemu_close to find > >> =A0>> =A0> > > >> =A0>> =A0the list and remove fd from it. But qemu_= close is currently consistent with > >> =A0>> =A0> > > >> =A0>> =A0qemu_open (which opens/dups fd), so addin= g additional logic might not be > >> =A0>> =A0> > > >> =A0>> =A0a very good idea. > >> =A0>> =A0> > > >> =A0> > >> =A0>> =A0> > > >> =A0> qemu_close is not appropriate place to deal w= ith something speciifc > >> =A0>> =A0> > > >> =A0> to the montor. > >> =A0>> =A0> > > >> =A0> > >> =A0>> =A0> > > >> =A0>> =A0I don't see any other solution, but I mig= ht miss something. > >> =A0>> =A0> > > >> =A0>> =A0What do you think? > >> =A0>> =A0> > > >> =A0> > >> =A0>> =A0> > > >> =A0> All callers of monitor_get_fd() will close() = the FD they get back. > >> =A0>> =A0> > > >> =A0> Thus monitor_get_fd() should remove it from t= he list when it returns > >> =A0>> =A0> > > >> =A0> it, and we should add API docs to monitor_get= _fd() to explain this. > >> =A0>> =A0> > > >> =A0> > >> =A0>> =A0> > > >> =A0Ok, it sounds reasonable. But monitor_get_fd is= only about outgoing migration. > >> =A0>> =A0> > > >> =A0But what about the incoming migration? It doesn= 't use monitor_get_fd but just > >> =A0>> =A0> > > >> =A0converts input string to int and use it as fd. > >> =A0>> =A0> > > > > >> =A0>> =A0> > > > The incoming migration expects the FD to be passed = into QEMU by the mgmt > >> =A0>> =A0> > > > app when it is exec'ing the QEMU binary. It doesn't= interact with the > >> =A0>> =A0> > > > monitor at all AFAIR. > >> =A0>> =A0> > > > > >> =A0>> =A0> > > > >> =A0>> =A0> > > Oh, sorry. This use case is not obvious. We used add-= fd to pass fd for > >> =A0>> =A0> > > migrate-incoming and such way has described problems. > >> =A0>> =A0> > > >> =A0>> =A0> > That's a bug in your usage of QEMU IMHO, as the incomin= g code is not > >> =A0>> =A0> > designed to use add-fd. > >> =A0>> =A0> > >> =A0>> =A0> Hmm, that's true - although: > >> =A0>> =A0> a) It's very non-obvious > >> =A0>> =A0> b) Unfortunate, since it would go well with -incoming def= er > >> =A0>> > >> =A0>> =A0Yeah I think this is a screw up on QMEU's part when introdu= cing 'defer'. > >> =A0>> > >> =A0>> =A0We should have mandated use of 'add-fd' when using 'defer',= since FD > >> =A0>> =A0inheritance-over-execve() should only be used for command l= ine args, > >> =A0>> =A0not monitor commands. > >> =A0>> > >> =A0>> =A0Not sure how to best fix this is QEMU though without breaki= ng back > >> =A0>> =A0compat for apps using 'defer' already. > >> =A0> > >> =A0> We could add mon-fd: transports that has the same behaviour as = now for > >> =A0> outgoing, and for incoming uses the add-fd stash. > >> =A0> > >> > >> =A0Oh, I'm sorry again. I think my suggestion about monitor_fd_param= wasn't > >> =A0relevant to this issue. If migrate-incoming + "fd:" + add-fd is a= n invalid use > >> =A0case, should we disallow this? > >> =A0I may add a check to fd_start_incoming_migration if fd is in mon = fds list. > >> =A0But I'm afraid there are users like me who are already using this= wrong use case. > >> =A0Because currently nothing in QEMU's docs disallow this. > >> > >> =A0So which solution is better in your opinion? > >> =A01) Disallow fd's from mon fds list in fd_start_incoming_migration > > > > I'm surprised anything could be doing that - how would a user know wh= at > > the correct fd index was? > > >=20 > Hmm, add-fd returns correct fd value. Maybe I din't catch you question.= .. I don't understand, where does it return it? > >> =A02) Allow these fds, but dup them or close them correctly > > > > I think I'd leave the current (confusing) fd: as it is, maybe put a n= ote > > in the manual. > > >=20 > So, using fd from fdset will be an undefined behavior, right? For incoming, yes. > >> =A0And how to migrate-incoming defer through fd correctly? > >> =A01) Add "mon-fd:" protocol to work with fds passed by "add-fd/remo= ve-fd" commands > >> =A0as suggested by Dave > > > > That's my preference; it's explicitly named and consistent, and it > > doesn't touch the existing fd code. > > >=20 > Ok, but please tell me what you think of my suggestion (2) about using = fd added > by the "getfd" command for incoming migration. It doesn't requires intr= oducing > new protocol and will be consistent with outgoing migration through fd. I worry how qemu knows whether the command means it comes from the getfd command or is actually a normal fd like now? Can you give an example. Dave > > > >> =A02) My suggestion about monitor_fd_param and make "fd:" for > >> =A0migrate/migrate-incoming consistent. So user will be able to use > >> =A0getfd + migrate-incoming > >> =A03) Both of them or something else > >> >=20 > Regards, > Yury >=20 -- 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 92A19C10F0E for ; Thu, 18 Apr 2019 16:04:43 +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 03DC020693 for ; Thu, 18 Apr 2019 16:04:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 03DC020693 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]:43736 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hH9Wk-0006qU-3G for qemu-devel@archiver.kernel.org; Thu, 18 Apr 2019 12:04:42 -0400 Received: from eggs.gnu.org ([209.51.188.92]:51086) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hH9VN-0006Dn-1V for qemu-devel@nongnu.org; Thu, 18 Apr 2019 12:03:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hH9VL-00033R-Cl for qemu-devel@nongnu.org; Thu, 18 Apr 2019 12:03:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53220) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hH9VL-00032r-4b for qemu-devel@nongnu.org; Thu, 18 Apr 2019 12:03:15 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A36A7307D771; Thu, 18 Apr 2019 16:03:05 +0000 (UTC) Received: from work-vm (ovpn-117-54.ams2.redhat.com [10.36.117.54]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5605160BE5; Thu, 18 Apr 2019 16:03:03 +0000 (UTC) Date: Thu, 18 Apr 2019 17:03:00 +0100 From: "Dr. David Alan Gilbert" To: Yury Kotov Message-ID: <20190418160300.GI2984@work-vm> References: <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> <20190415113045.GI2852@work-vm> <612681555412465@iva6-8a76e93b6298.qloud-c.yandex.net> <20190418141956.GF2984@work-vm> <1285061555601789@iva6-8a76e93b6298.qloud-c.yandex.net> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline In-Reply-To: <1285061555601789@iva6-8a76e93b6298.qloud-c.yandex.net> User-Agent: Mutt/1.11.4 (2019-03-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Thu, 18 Apr 2019 16:03:13 +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: "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: <20190418160300.p5eelEB1yk_PxTuo4ZDWC39RAVYKUCJv74xzfVtOMck@z> * Yury Kotov (yury-kotov@yandex-team.ru) wrote: > 18.04.2019, 17:20, "Dr. David Alan Gilbert" : > > * Yury Kotov (yury-kotov@yandex-team.ru) wrote: > >> =A015.04.2019, 14:30, "Dr. David Alan Gilbert" = : > >> =A0> * Daniel P. Berrang=E9 (berrange@redhat.com) wrote: > >> =A0>> =A0On Mon, Apr 15, 2019 at 12:15:12PM +0100, Dr. David Alan Gi= lbert wrote: > >> =A0>> =A0> * Daniel P. Berrang=E9 (berrange@redhat.com) wrote: > >> =A0>> =A0> > On Mon, Apr 15, 2019 at 01:33:21PM +0300, Yury Kotov wr= ote: > >> =A0>> =A0> > > 15.04.2019, 13:25, "Daniel P. Berrang=E9" : > >> =A0>> =A0> > > > On Mon, Apr 15, 2019 at 01:17:06PM +0300, Yury Koto= v wrote: > >> =A0>> =A0> > > >> =A015.04.2019, 13:11, "Daniel P. Berrang=E9" : > >> =A0>> =A0> > > >> =A0> On Mon, Apr 15, 2019 at 12:50:08PM +0300, Yur= y Kotov wrote: > >> =A0>> =A0> > > >> =A0>> =A0Hi, > >> =A0>> =A0> > > >> =A0>> > >> =A0>> =A0> > > >> =A0>> =A0Just to clarify. I see two possible solut= ions: > >> =A0>> =A0> > > >> =A0>> > >> =A0>> =A0> > > >> =A0>> =A01) Since the migration code doesn't recei= ve fd, it isn't responsible for > >> =A0>> =A0> > > >> =A0>> =A0closing it. So, it may be better to use m= igrate_fd_param for both > >> =A0>> =A0> > > >> =A0>> =A0incoming/outgoing and add dupping for mig= rate_fd_param. Thus, clients must > >> =A0>> =A0> > > >> =A0>> =A0close the fd themselves. But existing cli= ents will have a leak. > >> =A0>> =A0> > > >> =A0> > >> =A0>> =A0> > > >> =A0> We can't break existing clients in this way a= s they are correctly > >> =A0>> =A0> > > >> =A0> using the monitor with its current semantics. > >> =A0>> =A0> > > >> =A0> > >> =A0>> =A0> > > >> =A0>> =A02) If we don't duplicate fd, then at leas= t we should remove fd from > >> =A0>> =A0> > > >> =A0>> =A0the corresponding list. Therefore, the so= lution is to fix qemu_close to find > >> =A0>> =A0> > > >> =A0>> =A0the list and remove fd from it. But qemu_= close is currently consistent with > >> =A0>> =A0> > > >> =A0>> =A0qemu_open (which opens/dups fd), so addin= g additional logic might not be > >> =A0>> =A0> > > >> =A0>> =A0a very good idea. > >> =A0>> =A0> > > >> =A0> > >> =A0>> =A0> > > >> =A0> qemu_close is not appropriate place to deal w= ith something speciifc > >> =A0>> =A0> > > >> =A0> to the montor. > >> =A0>> =A0> > > >> =A0> > >> =A0>> =A0> > > >> =A0>> =A0I don't see any other solution, but I mig= ht miss something. > >> =A0>> =A0> > > >> =A0>> =A0What do you think? > >> =A0>> =A0> > > >> =A0> > >> =A0>> =A0> > > >> =A0> All callers of monitor_get_fd() will close() = the FD they get back. > >> =A0>> =A0> > > >> =A0> Thus monitor_get_fd() should remove it from t= he list when it returns > >> =A0>> =A0> > > >> =A0> it, and we should add API docs to monitor_get= _fd() to explain this. > >> =A0>> =A0> > > >> =A0> > >> =A0>> =A0> > > >> =A0Ok, it sounds reasonable. But monitor_get_fd is= only about outgoing migration. > >> =A0>> =A0> > > >> =A0But what about the incoming migration? It doesn= 't use monitor_get_fd but just > >> =A0>> =A0> > > >> =A0converts input string to int and use it as fd. > >> =A0>> =A0> > > > > >> =A0>> =A0> > > > The incoming migration expects the FD to be passed = into QEMU by the mgmt > >> =A0>> =A0> > > > app when it is exec'ing the QEMU binary. It doesn't= interact with the > >> =A0>> =A0> > > > monitor at all AFAIR. > >> =A0>> =A0> > > > > >> =A0>> =A0> > > > >> =A0>> =A0> > > Oh, sorry. This use case is not obvious. We used add-= fd to pass fd for > >> =A0>> =A0> > > migrate-incoming and such way has described problems. > >> =A0>> =A0> > > >> =A0>> =A0> > That's a bug in your usage of QEMU IMHO, as the incomin= g code is not > >> =A0>> =A0> > designed to use add-fd. > >> =A0>> =A0> > >> =A0>> =A0> Hmm, that's true - although: > >> =A0>> =A0> a) It's very non-obvious > >> =A0>> =A0> b) Unfortunate, since it would go well with -incoming def= er > >> =A0>> > >> =A0>> =A0Yeah I think this is a screw up on QMEU's part when introdu= cing 'defer'. > >> =A0>> > >> =A0>> =A0We should have mandated use of 'add-fd' when using 'defer',= since FD > >> =A0>> =A0inheritance-over-execve() should only be used for command l= ine args, > >> =A0>> =A0not monitor commands. > >> =A0>> > >> =A0>> =A0Not sure how to best fix this is QEMU though without breaki= ng back > >> =A0>> =A0compat for apps using 'defer' already. > >> =A0> > >> =A0> We could add mon-fd: transports that has the same behaviour as = now for > >> =A0> outgoing, and for incoming uses the add-fd stash. > >> =A0> > >> > >> =A0Oh, I'm sorry again. I think my suggestion about monitor_fd_param= wasn't > >> =A0relevant to this issue. If migrate-incoming + "fd:" + add-fd is a= n invalid use > >> =A0case, should we disallow this? > >> =A0I may add a check to fd_start_incoming_migration if fd is in mon = fds list. > >> =A0But I'm afraid there are users like me who are already using this= wrong use case. > >> =A0Because currently nothing in QEMU's docs disallow this. > >> > >> =A0So which solution is better in your opinion? > >> =A01) Disallow fd's from mon fds list in fd_start_incoming_migration > > > > I'm surprised anything could be doing that - how would a user know wh= at > > the correct fd index was? > > >=20 > Hmm, add-fd returns correct fd value. Maybe I din't catch you question.= .. I don't understand, where does it return it? > >> =A02) Allow these fds, but dup them or close them correctly > > > > I think I'd leave the current (confusing) fd: as it is, maybe put a n= ote > > in the manual. > > >=20 > So, using fd from fdset will be an undefined behavior, right? For incoming, yes. > >> =A0And how to migrate-incoming defer through fd correctly? > >> =A01) Add "mon-fd:" protocol to work with fds passed by "add-fd/remo= ve-fd" commands > >> =A0as suggested by Dave > > > > That's my preference; it's explicitly named and consistent, and it > > doesn't touch the existing fd code. > > >=20 > Ok, but please tell me what you think of my suggestion (2) about using = fd added > by the "getfd" command for incoming migration. It doesn't requires intr= oducing > new protocol and will be consistent with outgoing migration through fd. I worry how qemu knows whether the command means it comes from the getfd command or is actually a normal fd like now? Can you give an example. Dave > > > >> =A02) My suggestion about monitor_fd_param and make "fd:" for > >> =A0migrate/migrate-incoming consistent. So user will be able to use > >> =A0getfd + migrate-incoming > >> =A03) Both of them or something else > >> >=20 > Regards, > Yury >=20 -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK