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 042F4E7717D for ; Mon, 9 Dec 2024 20:56:32 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tKknk-0007AI-MB; Mon, 09 Dec 2024 15:56:20 -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 1tKkni-00072s-UI for qemu-devel@nongnu.org; Mon, 09 Dec 2024 15:56:18 -0500 Received: from smtp-out1.suse.de ([195.135.223.130]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1tKknh-00056b-G9 for qemu-devel@nongnu.org; Mon, 09 Dec 2024 15:56:18 -0500 Received: from imap1.dmz-prg2.suse.org (unknown [10.150.64.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 001B621160; Mon, 9 Dec 2024 20:56:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1733777776; h=from:from:reply-to: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=PIxO94mbL+2zIie3MWQXfyi9U4gIDYk6LId1H78G+WA=; b=Sa0+OyHFGtNPoOM0nbgTtkKS6b90nHa/GxRr7/6utglUsPzN5EjgXTvgDsz6JWvMBiUal2 oDrSFzpawEgOdW36RYRg8hrx1QFx8eW5w7Du81T7pBxkJzBcMXD5Asac3cFYY1sRDulwwm uuKGn+TI7w8N/eJKQD370skVyRYf8DE= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1733777776; h=from:from:reply-to: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=PIxO94mbL+2zIie3MWQXfyi9U4gIDYk6LId1H78G+WA=; b=AukuxWYc+G0GVa/I+DqmNF3ACDgM6pRUONT6xD7bgTI1gmg2qQVQUtYSJuetuMgnLZD1jX KYzVQ/6YYudG6gCw== Authentication-Results: smtp-out1.suse.de; none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1733777776; h=from:from:reply-to: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=PIxO94mbL+2zIie3MWQXfyi9U4gIDYk6LId1H78G+WA=; b=Sa0+OyHFGtNPoOM0nbgTtkKS6b90nHa/GxRr7/6utglUsPzN5EjgXTvgDsz6JWvMBiUal2 oDrSFzpawEgOdW36RYRg8hrx1QFx8eW5w7Du81T7pBxkJzBcMXD5Asac3cFYY1sRDulwwm uuKGn+TI7w8N/eJKQD370skVyRYf8DE= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1733777776; h=from:from:reply-to: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=PIxO94mbL+2zIie3MWQXfyi9U4gIDYk6LId1H78G+WA=; b=AukuxWYc+G0GVa/I+DqmNF3ACDgM6pRUONT6xD7bgTI1gmg2qQVQUtYSJuetuMgnLZD1jX KYzVQ/6YYudG6gCw== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 7969B138D2; Mon, 9 Dec 2024 20:56:15 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id PYioD29ZV2dtcgAAD6G6ig (envelope-from ); Mon, 09 Dec 2024 20:56:15 +0000 From: Fabiano Rosas To: Peter Xu , qemu-devel@nongnu.org Cc: Prasad Pandit , "Maciej S . Szmigiero" , =?utf-8?Q?C=C3=A9dric?= Le Goater , Alex Williamson , peterx@redhat.com, Avihai Horon Subject: Re: [PATCH v3 7/7] migration/multifd: Document the reason to sync for save_setup() In-Reply-To: <20241206224755.1108686-8-peterx@redhat.com> References: <20241206224755.1108686-1-peterx@redhat.com> <20241206224755.1108686-8-peterx@redhat.com> Date: Mon, 09 Dec 2024 17:56:12 -0300 Message-ID: <87r06ga843.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[99.99%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-0.999]; MIME_GOOD(-0.10)[text/plain]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; MISSING_XM_UA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_SEVEN(0.00)[8]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FUZZY_BLOCKED(0.00)[rspamd.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email,suse.de:mid] Received-SPF: pass client-ip=195.135.223.130; envelope-from=farosas@suse.de; helo=smtp-out1.suse.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=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: , 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: > It's not straightforward to see why src QEMU needs to sync multifd during > setup() phase. After all, there's no page queued at that point. > > For old QEMUs, there's a solid reason: EOS requires it to work. While it's > clueless on the new QEMUs which do not take EOS message as sync requests. > > One will figure that out only when this is conditionally removed. In fact, > the author did try it out. Logically we could still avoid doing this on > new machine types, however that needs a separate compat field and that can > be an overkill in some trivial overhead in setup() phase. > > Let's instead document it completely, to avoid someone else tries this > again and do the debug one more time, or anyone confused on why this ever > existed. > > Signed-off-by: Peter Xu Reviewed-by: Fabiano Rosas