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 9B74BC25B74 for ; Mon, 27 May 2024 10:54:01 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sBXyu-0006ks-Th; Mon, 27 May 2024 06:53:32 -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 1sBXys-0006jl-AJ for qemu-devel@nongnu.org; Mon, 27 May 2024 06:53:30 -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 1sBXyq-000237-LI for qemu-devel@nongnu.org; Mon, 27 May 2024 06:53:30 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1716807208; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=06/efgP++cvCr9aQmle2exNHgKBPrQtzUEN3DA3ZL/Q=; b=AZJHZQ4Y5GDTY3+EkkcDkvZR025KMRhm9dHTq8+h9hhAijMhx1bVlkqw6KqPhYUQ74mKZn n6A2wXMEE1Rw3GpHbUr6NYG8gEVU+3T0wxwnciFNtEvXC4mYt/KSqFl9xw8/Q7nkksuXYr qjnJiY5euGmzGMtPN+GEq1XrE96Fb/k= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-417-2YSbDu33MIilaWnXzi9_qQ-1; Mon, 27 May 2024 06:53:23 -0400 X-MC-Unique: 2YSbDu33MIilaWnXzi9_qQ-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (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 mimecast-mx02.redhat.com (Postfix) with ESMTPS id 3577629AA39D; Mon, 27 May 2024 10:53:23 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.193.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 147D9491032; Mon, 27 May 2024 10:53:23 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 070D421E6757; Mon, 27 May 2024 12:53:22 +0200 (CEST) From: Markus Armbruster To: Peter Xu Cc: qemu-devel@nongnu.org, philmd@linaro.org, fam@euphon.net, kwolf@redhat.com, hreitz@redhat.com, marcandre.lureau@redhat.com, farosas@suse.de, pbonzini@redhat.com, richard.henderson@linaro.org, qemu-block@nongnu.org Subject: Re: [PATCH 5/6] migration: Rephrase message on failure to save / load Xen device state In-Reply-To: (Peter Xu's message of "Thu, 23 May 2024 15:43:32 -0400") References: <20240513141703.549874-1-armbru@redhat.com> <20240513141703.549874-6-armbru@redhat.com> Date: Mon, 27 May 2024 12:53:22 +0200 Message-ID: <87wmnfcyql.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@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=-0.034, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Peter Xu writes: > On Mon, May 13, 2024 at 04:17:02PM +0200, Markus Armbruster wrote: >> Functions that use an Error **errp parameter to return errors should >> not also report them to the user, because reporting is the caller's >> job. When the caller does, the error is reported twice. When it >> doesn't (because it recovered from the error), there is no error to >> report, i.e. the report is bogus. >> >> qmp_xen_save_devices_state() and qmp_xen_load_devices_state() violate >> this principle: they call qemu_save_device_state() and >> qemu_loadvm_state(), which call error_report_err(). >> >> I wish I could clean this up now, but migration's error reporting is >> too complicated (confused?) for me to mess with it. > > :-( If I understood how it's *supposed* to work, I might have a chance... I can see a mixture of reporting errors directly (with error_report() & friends), passing them to callers (via Error **errp), and storing them in / retrieving them from MigrationState member @error. This can't be right. I think a necessary first step towards getting it right is a shared understanding how errors are to be handled in migration code. This includes how error data should flow from error source to error sink, and what the possible sinks are. >> Instead, I'm merely improving the error reported by >> qmp_xen_load_devices_state() and qmp_xen_load_devices_state() to the >> QMP core from >> >> An IO error has occurred >> >> to >> saving Xen device state failed >> >> and >> >> loading Xen device state failed >> >> respectively. >> >> Signed-off-by: Markus Armbruster > > Acked-by: Peter Xu Thanks!