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 10406C43334 for ; Tue, 26 Jul 2022 08:46:30 +0000 (UTC) Received: from localhost ([::1]:33698 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oGGCy-00064v-TQ for qemu-devel@archiver.kernel.org; Tue, 26 Jul 2022 04:46:28 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:52594) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oGGBA-0004nJ-2L for qemu-devel@nongnu.org; Tue, 26 Jul 2022 04:44:36 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:40056) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oGGB6-0008Cx-EI for qemu-devel@nongnu.org; Tue, 26 Jul 2022 04:44:33 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1658825071; 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=jqedxUlUnrbHMRPpLrfcDt66W0YkSUCxzzENrK/g79s=; b=Tub0pS7jsMEyrRxaY2cCSO2Cl3+CEST0NGtfv1VoiJPACAmc/h1x9t1lkRgxnHPHLGSxqu gOPnCvuej+se/vTOWxt9Tm4HIew/mFLrIch6/KhVd/jNBQL1o6841lkgivc9f1cc25VxS8 +OjQNjoyqC92cLrWzjS8Urcm+y887Ro= 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-333-D5htmdXaNN-GkSXaR85Hjw-1; Tue, 26 Jul 2022 04:44:30 -0400 X-MC-Unique: D5htmdXaNN-GkSXaR85Hjw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 1CC9C1C06ED5 for ; Tue, 26 Jul 2022 08:44:30 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.211]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 01972400F8F0; Tue, 26 Jul 2022 08:44:27 +0000 (UTC) Date: Tue, 26 Jul 2022 09:44:25 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: marcandre.lureau@redhat.com Cc: qemu-devel@nongnu.org, "reviewer:Incompatible changes" , kraxel@redhat.com, Paolo Bonzini Subject: Re: [PATCH] RFC: char: deprecate usage of bidirectional pipe Message-ID: References: <20220726083232.2567756-1-marcandre.lureau@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220726083232.2567756-1-marcandre.lureau@redhat.com> User-Agent: Mutt/2.2.6 (2022-06-05) X-Scanned-By: MIMEDefang 2.84 on 10.11.54.2 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: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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" On Tue, Jul 26, 2022 at 12:32:32PM +0400, marcandre.lureau@redhat.com wrote: > From: Marc-André Lureau > > As Ed Swierk explained back in 2006: > https://lists.nongnu.org/archive/html/qemu-devel/2006-12/msg00160.html > > "When qemu writes into the pipe, it immediately reads back what it just > wrote and treats it as a monitor command, endlessly breathing its own > exhaust." > > This is similarly confusing when using the chardev with a serial device, > as reported in https://bugzilla.redhat.com/show_bug.cgi?id=2106975. > > It seems we have kept the support for bidirectional pipes for historical > reasons and odd systems, however it's not documented in qemu -chardev > options. I suggest to stop supporting it, for portability reasons. Hmm, I always assumed that in this scenario the pipe was operating in output-only mode. Obviously not the case with the code as it exists, but perhaps this would be useful ? eg its good as a serial console logging mechanism at least. > > Signed-off-by: Marc-André Lureau > --- > docs/about/deprecated.rst | 6 ++++++ > chardev/char-pipe.c | 4 ++++ > 2 files changed, 10 insertions(+) > > diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst > index 7ee26626d5cf..dd5ca30d527b 100644 > --- a/docs/about/deprecated.rst > +++ b/docs/about/deprecated.rst > @@ -45,6 +45,12 @@ transmit audio through the VNC protocol. > ``tty`` and ``parport`` are aliases that will be removed. Instead, the > actual backend names ``serial`` and ``parallel`` should be used. > > +``-chardev pipe`` support for bidirectional pipes (since 7.1) > +'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' > + > +For portability reasons, the support for bidirectional ``pipe`` will > +be removed. Instead, use ``file.in`` & ``file.out`` unidirectional pipes. > + > Short-form boolean options (since 6.0) > '''''''''''''''''''''''''''''''''''''' > > diff --git a/chardev/char-pipe.c b/chardev/char-pipe.c > index 66d3b8509183..7db963035e7d 100644 > --- a/chardev/char-pipe.c > +++ b/chardev/char-pipe.c > @@ -27,6 +27,7 @@ > #include "qemu/main-loop.h" > #include "qemu/module.h" > #include "qemu/option.h" > +#include "qemu/error-report.h" > #include "chardev/char.h" > > #ifdef _WIN32 > @@ -142,6 +143,9 @@ static void qemu_chr_open_pipe(Chardev *chr, > if (fd_out >= 0) { > close(fd_out); > } > + warn_report("Support for bidirectional pipe is deprecated,"); > + warn_report("please use portable one-way pipes instead (%s.in & %s.out).", > + filename, filename); > TFR(fd_in = fd_out = qemu_open_old(filename, O_RDWR | O_BINARY)); > if (fd_in < 0) { > error_setg_file_open(errp, errno, filename); > -- > 2.37.0.rc0 > 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 :|