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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 502DEC4332F for ; Wed, 16 Nov 2022 11:28:31 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ovGaH-0001z0-Kq; Wed, 16 Nov 2022 06:28:01 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ovGaF-0001yo-Lj for qemu-devel@nongnu.org; Wed, 16 Nov 2022 06:27:59 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ovGaD-0001A6-5v for qemu-devel@nongnu.org; Wed, 16 Nov 2022 06:27:59 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1668598076; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=prWJVNrtdnQmExpy4Q79NlkkRUIXmPwZ6liRVvVGjIM=; b=FERZOgDXmS9t9lK31DGP9oXi/HCJ8D3VROSOCLUnw9GQpUnUFl2N57+hT+hcw3igf/jST9 1kdIVTodcoyabp2Pd8pziJh6Iz+DPEAi+3/St6DAz2o0ShJUjYHTl3Hr6cRSSLljjmQo8C /otNLvxWW0q9PYnihHdBkOnnA8KP1c0= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-221-UcLreBl2MXKBkbFoXdRh3g-1; Wed, 16 Nov 2022 06:27:52 -0500 X-MC-Unique: UcLreBl2MXKBkbFoXdRh3g-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 69F963810D56; Wed, 16 Nov 2022 11:27:52 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.81]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7D327492B1A; Wed, 16 Nov 2022 11:27:51 +0000 (UTC) Date: Wed, 16 Nov 2022 11:27:48 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: "manish.mishra" Cc: qemu-devel@nongnu.org, peterx@redhat.com, prerna.saxena@nutanix.com, quintela@redhat.com Subject: Re: [PATCH v2] migration: check magic value for deciding the mapping of channels Message-ID: References: <20221107165159.49534-1-manish.mishra@nutanix.com> <7a01e23c-3148-4a7d-4fa8-85ca9c0be6d3@nutanix.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <7a01e23c-3148-4a7d-4fa8-85ca9c0be6d3@nutanix.com> User-Agent: Mutt/2.2.7 (2022-08-07) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Wed, Nov 16, 2022 at 04:49:18PM +0530, manish.mishra wrote: > > On 16/11/22 12:20 am, Daniel P. Berrangé wrote: > > On Tue, Nov 15, 2022 at 06:11:30PM +0000, Daniel P. Berrangé wrote: > > > On Mon, Nov 07, 2022 at 04:51:59PM +0000, manish.mishra wrote: > > > > Current logic assumes that channel connections on the destination side are > > > > always established in the same order as the source and the first one will > > > > always be the main channel followed by the multifid or post-copy > > > > preemption channel. This may not be always true, as even if a channel has a > > > > connection established on the source side it can be in the pending state on > > > > the destination side and a newer connection can be established first. > > > > Basically causing out of order mapping of channels on the destination side. > > > > Currently, all channels except post-copy preempt send a magic number, this > > > > patch uses that magic number to decide the type of channel. This logic is > > > > applicable only for precopy(multifd) live migration, as mentioned, the > > > > post-copy preempt channel does not send any magic number. Also, tls live > > > > migrations already does tls handshake before creating other channels, so > > > > this issue is not possible with tls, hence this logic is avoided for tls > > > > live migrations. This patch uses MSG_PEEK to check the magic number of > > > > channels so that current data/control stream management remains > > > > un-effected. > > > > > > > > Suggested-by: Daniel P. Berrangé > > > > Signed-off-by: manish.mishra > > > > > > > > v2: > > > > TLS does not support MSG_PEEK, so V1 was broken for tls live > > > > migrations. For tls live migration, while initializing main channel > > > > tls handshake is done before we can create other channels, so this > > > > issue is not possible for tls live migrations. In V2 added a check > > > > to avoid checking magic number for tls live migration and fallback > > > > to older method to decide mapping of channels on destination side. > > > > --- > > > > include/io/channel.h | 25 +++++++++++++++++++++++ > > > > io/channel-socket.c | 27 ++++++++++++++++++++++++ > > > > io/channel.c | 39 +++++++++++++++++++++++++++++++++++ > > > > migration/migration.c | 44 +++++++++++++++++++++++++++++----------- > > > > migration/multifd.c | 12 ++++------- > > > > migration/multifd.h | 2 +- > > > > migration/postcopy-ram.c | 5 +---- > > > > migration/postcopy-ram.h | 2 +- > > > > 8 files changed, 130 insertions(+), 26 deletions(-) > > > This should be two commits, because the 'io' and 'migration' > > > code are two separate subsystems in QEMU. > > > > > > > diff --git a/include/io/channel.h b/include/io/channel.h > > > > index c680ee7480..74177aeeea 100644 > > > > --- a/include/io/channel.h > > > > +++ b/include/io/channel.h > > > > @@ -115,6 +115,10 @@ struct QIOChannelClass { > > > > int **fds, > > > > size_t *nfds, > > > > Error **errp); > > > > + ssize_t (*io_read_peek)(QIOChannel *ioc, > > > > + void *buf, > > > > + size_t nbytes, > > > > + Error **errp); > > > This API should be called "io_read_peekv" and use > > > "const struct iovec *iov", such that is matches the > > > design of 'io_readv'. > > > > > > There should also be a QIOChannelFeature flag > > > registered to indicate whether a given channel > > > impl supports peeking at data. > > > > > > > > > > @@ -475,6 +479,27 @@ int qio_channel_write_all(QIOChannel *ioc, > > > > size_t buflen, > > > > Error **errp); > > > > +/** > > > > + * qio_channel_read_peek_all: > > > > + * @ioc: the channel object > > > > + * @buf: the memory region to read in data > > > > + * @nbytes: the number of bytes to read > > > > + * @errp: pointer to a NULL-initialized error object > > > > + * > > > > + * Read given @nbytes data from peek of channel into > > > > + * memory region @buf. > > > > + * > > > > + * The function will be blocked until read size is > > > > + * equal to requested size. > > > > + * > > > > + * Returns: 1 if all bytes were read, 0 if end-of-file > > > > + * occurs without data, or -1 on error > > > > + */ > > > > +int qio_channel_read_peek_all(QIOChannel *ioc, > > > > + void* buf, > > > > + size_t nbytes, > > > > + Error **errp); > > > There should be qio_channel_read_peek, qio_channel_read_peekv, > > > qio_channel_read_peek_all and qio_channel_read_peekv_all. > > Actually ignore that. We should not add any new APIs at > > all. Instead the io_readv callback, and the qio_channel_read*all() > > methods should gain a 'int flags' parameter, in the same way that > > the write methods have one. Then there should be as > > QIO_CHANNEL_READ_FLAG_PEEK constant defined. > > Hi Daniel, As MSG_PEEK always reads from top even if there were > previos partial reads, so current |qio_channel_readv_all_eofmay > not work? I can keep things upto ||qio_channel_readv as common > for both with flags parameters but have separate > ||qio_channel_readv_peek_all_eof? Does something like that works.||| Simplest is probably to just not add 'flags' to the 'all' variants, just the non-'all' varants. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|