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 5D059C433FE for ; Wed, 23 Nov 2022 16:20:24 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oxsTF-000737-0C; Wed, 23 Nov 2022 11:19:34 -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 1oxsTD-00072a-3k for qemu-devel@nongnu.org; Wed, 23 Nov 2022 11:19:31 -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 1oxsTA-0005iE-Tj for qemu-devel@nongnu.org; Wed, 23 Nov 2022 11:19:30 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1669220367; 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=/H2u6a69ticqBa17yNdaEiMNfIgrZSPYXmIQEndMmzs=; b=TdZFk7GbhnH7DE59q9Psw4mdvPs46koXXQKeQw2TpqGWHBeaSsOxoTEPuaJK14+3i7/+Gs VeqPZhB5O2VbQDEUOoiFMnudt40ghh/fFR/B9u9DmcbIvb6u/szrd8sesOcfFZEgX6wDE8 sxiCWe8s6WYATx3D4L8jd6vomSxQWOY= 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-467-kA-rxFSROPGD0ZoPfmH9Wg-1; Wed, 23 Nov 2022 11:19:26 -0500 X-MC-Unique: kA-rxFSROPGD0ZoPfmH9Wg-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 1ACA53C01DE7; Wed, 23 Nov 2022 16:19:26 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.56]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C939F492B07; Wed, 23 Nov 2022 16:19:24 +0000 (UTC) Date: Wed, 23 Nov 2022 16:19:20 +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, dgilbert@redhat.com, lsoaresp@redhat.com Subject: Re: [PATCH v4 2/2] migration: check magic value for deciding the mapping of channels Message-ID: References: <20221123150527.24608-1-manish.mishra@nutanix.com> <20221123150527.24608-3-manish.mishra@nutanix.com> <9cdace7b-7fd2-7c9a-01a2-14bef1473136@nutanix.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <9cdace7b-7fd2-7c9a-01a2-14bef1473136@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 23, 2022 at 09:34:35PM +0530, manish.mishra wrote: > > On 23/11/22 9:28 pm, Daniel P. Berrangé wrote: > > On Wed, Nov 23, 2022 at 03:05:27PM +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 read peek to check the magic number of > > > channels so that current data/control stream management remains > > > un-effected. > > > > > > Reviewed-by: Peter Xu > > > Reviewed-by: Daniel P. Berrangé > > Suggested-by: Daniel P. Berrangé > > Signed-off-by: manish.mishra > > > --- > > > migration/channel.c | 46 ++++++++++++++++++++++++++++++++++++++++ > > > migration/channel.h | 5 +++++ > > > migration/migration.c | 45 ++++++++++++++++++++++++++++----------- > > > migration/multifd.c | 12 ++++------- > > > migration/multifd.h | 2 +- > > > migration/postcopy-ram.c | 5 +---- > > > migration/postcopy-ram.h | 2 +- > > > 7 files changed, 91 insertions(+), 26 deletions(-) > > > > > > diff --git a/migration/channel.c b/migration/channel.c > > > index 1b0815039f..a4600f52c5 100644 > > > --- a/migration/channel.c > > > +++ b/migration/channel.c > > > @@ -92,3 +92,49 @@ void migration_channel_connect(MigrationState *s, > > > migrate_fd_connect(s, error); > > > error_free(error); > > > } > > > + > > > + > > > +/** > > > + * @migration_channel_read_peek - Read from the peek of migration channel, > > > + * without actually removing it from channel buffer. > > > + * > > > + * @ioc: the channel object > > > + * @buf: the memory region to read data into > > > + * @buflen: the number of bytes to read in @buf > > > + * @errp: pointer to a NULL-initialized error object > > > + * > > > + * Returns 0 if successful, returns -1 and sets @errp if fails. > > > + */ > > > +int migration_channel_read_peek(QIOChannel *ioc, > > > + const char *buf, > > > + const size_t buflen, > > > + Error **errp) > > > +{ > > > + ssize_t len = 0; > > > + struct iovec iov = { .iov_base = (char *)buf, .iov_len = buflen }; > > > + > > > + while (len < buflen) { > > > + len = qio_channel_readv_full(ioc, &iov, 1, NULL, > > > + NULL, QIO_CHANNEL_READ_FLAG_MSG_PEEK, errp); > > > + > > > + if (len == QIO_CHANNEL_ERR_BLOCK) { > > > + if (qemu_in_coroutine()) { > > > + /* 1ms sleep. */ > > > + qemu_co_sleep_ns(QEMU_CLOCK_REALTIME, 1000000); > > > + } else { > > > + qio_channel_wait(ioc, G_IO_IN); > > > + } > > > + continue; > > > + } > > > + if (len == 0) { > > > + error_setg(errp, > > > + "Unexpected end-of-file on channel"); > > > + return -1; > > > + } > > > + if (len < 0) { > > > + return -1; > > > + } > > > + } > > This busy waits when len > 0 and < buflen > > > > > > With regards, > > Daniel > > Sorry,   Daniel, may be i misunderstood something from earlier > discussions. I thought we discussed we may not prevent it from > looping multiple times but we can  qemu_co_sleep_ns after every > retry to deal with busy wait? You're only calling qemu_co_sleep_ns when you get ERR_BLOCK though. That will happen the first time when 0 bytes are pending. Once 2 bytes arrive and we're waiting for 2 more, this code will busy wait instead of calling qemu_co_sleep_ns again, because len==2 in that case. 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 :|