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 A3177CA0EE4 for ; Wed, 20 Aug 2025 14:43:29 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uok1X-0004UH-GQ; Wed, 20 Aug 2025 10:42:48 -0400 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 1uok1S-0004Te-Fl for qemu-devel@nongnu.org; Wed, 20 Aug 2025 10:42:42 -0400 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 1uok1P-0001S7-Gx for qemu-devel@nongnu.org; Wed, 20 Aug 2025 10:42:42 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1755700956; 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=SKnS7joAat6C+x95tT//zwXeO8Am03pn+XmO3KRRz+Q=; b=FjDzUkW1pPnt4zJnPT464qYqJF7Zs+bf6jgx5DImh+J2YP3NF4zB5lMpNaof94meTP+Y1q uZSguyXum/ZqnIG9LlrywXfl/OQdCc6WpF3NUW6qohMjsyMAhAIhhKvoetTxiunno7iBhB KovPapNfDDfj6mMQojYFlxb237s42QI= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-587-Fdo2RvAvO12gb9sKlxQ-UQ-1; Wed, 20 Aug 2025 10:42:33 -0400 X-MC-Unique: Fdo2RvAvO12gb9sKlxQ-UQ-1 X-Mimecast-MFC-AGG-ID: Fdo2RvAvO12gb9sKlxQ-UQ_1755700952 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 4B997195608A; Wed, 20 Aug 2025 14:42:31 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.164]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 6DCB3180044F; Wed, 20 Aug 2025 14:42:24 +0000 (UTC) Date: Wed, 20 Aug 2025 15:42:21 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Peter Xu Cc: Vladimir Sementsov-Ogievskiy , mst@redhat.com, farosas@suse.de, raphael@enfabrica.net, sgarzare@redhat.com, marcandre.lureau@redhat.com, pbonzini@redhat.com, kwolf@redhat.com, hreitz@redhat.com, eblake@redhat.com, armbru@redhat.com, qemu-devel@nongnu.org, qemu-block@nongnu.org, steven.sistare@oracle.com, den-plotnikov@yandex-team.ru Subject: Re: [PATCH 26/33] io/channel-socket: introduce qio_channel_socket_keep_nonblock() Message-ID: References: <20250813164856.950363-1-vsementsov@yandex-team.ru> <20250813164856.950363-27-vsementsov@yandex-team.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-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, Aug 20, 2025 at 10:37:41AM -0400, Peter Xu wrote: > On Wed, Aug 20, 2025 at 02:43:54PM +0100, Daniel P. Berrangé wrote: > > On Wed, Aug 20, 2025 at 09:27:09AM -0400, Peter Xu wrote: > > > On Wed, Aug 13, 2025 at 07:48:47PM +0300, Vladimir Sementsov-Ogievskiy wrote: > > > > Add a possibility to keep socket non-block status when passing > > > > through qio channel. We need this to support migration of open > > > > fds through migration channel. > > > > > > > > Signed-off-by: Vladimir Sementsov-Ogievskiy > > > > --- > > > > include/io/channel-socket.h | 3 +++ > > > > io/channel-socket.c | 16 ++++++++++++---- > > > > 2 files changed, 15 insertions(+), 4 deletions(-) > > > > > > > > diff --git a/include/io/channel-socket.h b/include/io/channel-socket.h > > > > index a88cf8b3a9..0a4327d745 100644 > > > > --- a/include/io/channel-socket.h > > > > +++ b/include/io/channel-socket.h > > > > @@ -49,6 +49,7 @@ struct QIOChannelSocket { > > > > socklen_t remoteAddrLen; > > > > ssize_t zero_copy_queued; > > > > ssize_t zero_copy_sent; > > > > + bool keep_nonblock; > > > > }; > > > > > > > > > > > > @@ -275,4 +276,6 @@ int qio_channel_socket_set_send_buffer(QIOChannelSocket *ioc, > > > > size_t size, > > > > Error **errp); > > > > > > > > +void qio_channel_socket_keep_nonblock(QIOChannel *ioc); > > > > + > > > > #endif /* QIO_CHANNEL_SOCKET_H */ > > > > diff --git a/io/channel-socket.c b/io/channel-socket.c > > > > index 3b7ca924ff..cd93d7f180 100644 > > > > --- a/io/channel-socket.c > > > > +++ b/io/channel-socket.c > > > > @@ -462,9 +462,16 @@ static void qio_channel_socket_finalize(Object *obj) > > > > } > > > > > > > > > > > > +void qio_channel_socket_keep_nonblock(QIOChannel *ioc) > > > > +{ > > > > + QIOChannelSocket *sioc = QIO_CHANNEL_SOCKET(ioc); > > > > + sioc->keep_nonblock = true; > > > > +} > > > > + > > > > + > > > > #ifndef WIN32 > > > > static void qio_channel_socket_copy_fds(struct msghdr *msg, > > > > - int **fds, size_t *nfds) > > > > + int **fds, size_t *nfds, bool set_block) > > > > { > > > > struct cmsghdr *cmsg; > > > > > > > > @@ -497,8 +504,9 @@ static void qio_channel_socket_copy_fds(struct msghdr *msg, > > > > continue; > > > > } > > > > > > > > - /* O_NONBLOCK is preserved across SCM_RIGHTS so reset it */ > > > > - qemu_socket_set_block(fd); > > > > + if (set_block) { > > > > + qemu_socket_set_block(fd); > > > > + } > > > > > > "keep_nonblock" as a feature in iochannel is slightly hard to digest. It > > > can also be read as "keep the fd to be always nonblocking". > > > > > > Is this feature required, or can this also be done in a get() or > > > post_load() on the other side to set nonblock to whatever it should be > > > (that dest QEMU should be aware of)? > > > > Either we preserve state of the flag when receiving the FD, > > or every QEMU backend that we're receiving FDs on behalf of > > needs to reset the flag when migration passes over the FD. > > > > The latter might actually be a more robust scheme. If we're > > migrating across QEMU versions, there is not a strict > > guarantee that the new QEMU version's backend will want the > > O_NONBLOCK flag in the same state as the old QEMU version. > > The code might have been re-written to work in a different > > way than previously. > > Good point. > > Do you remember why we reset that in the very initial git commit? Historical needs to receive FDs in QEMU have been in relation to external non-QEMU processes. We reset the blocking state to ensure that all FDs we receive have a well defined initial state, and the QEMU backends consuming the FDs can then alter that as required. 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 :|