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 C8E20C001E0 for ; Mon, 23 Oct 2023 15:03:47 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1quwSj-0001A9-Pc; Mon, 23 Oct 2023 11:03:25 -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 1quwSe-00018x-B1 for qemu-devel@nongnu.org; Mon, 23 Oct 2023 11:03:21 -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 1quwSc-000524-9A for qemu-devel@nongnu.org; Mon, 23 Oct 2023 11:03:20 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1698073397; 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=ur4OhFk/SSrt5Pk1EGPmBChfmE074rgrKaMwV3t41YQ=; b=K75hbPIB8sfx7xlw6VqaWn9wdFcw+4rs7VUsKGAT0jFwCBvu4p7E01F7Zs9tTh0pPKmogn 0sM9cHKQW4PjR9Z2C5748P7O4HsShEDAGDGudS/9bdfLjhSfGz4eUS2W4w2IRY+EWzOL3Q 3IpPdhWS3lPDwWpKEfz2ocfIkIPxt6c= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-329-1gxkFSejMYK-C-2gSwb_IA-1; Mon, 23 Oct 2023 11:02:57 -0400 X-MC-Unique: 1gxkFSejMYK-C-2gSwb_IA-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 08EA2811E7B; Mon, 23 Oct 2023 15:02:57 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.124]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0EBA7492BFC; Mon, 23 Oct 2023 15:02:55 +0000 (UTC) Date: Mon, 23 Oct 2023 16:02:54 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Steven Sistare Cc: qemu-devel@nongnu.org, Juan Quintela , Peter Xu , Fabiano Rosas , Leonardo Bras Subject: Re: [PATCH V1 2/4] migration: per-mode blockers Message-ID: References: <1697748466-373230-1-git-send-email-steven.sistare@oracle.com> <1697748466-373230-3-git-send-email-steven.sistare@oracle.com> <61ccb916-e50f-4b05-a5bd-5fcf8bf0177f@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <61ccb916-e50f-4b05-a5bd-5fcf8bf0177f@oracle.com> User-Agent: Mutt/2.2.9 (2022-11-12) X-Scanned-By: MIMEDefang 3.4.1 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_H4=0.001, RCVD_IN_MSPIKE_WL=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 Mon, Oct 23, 2023 at 10:37:59AM -0400, Steven Sistare wrote: > On 10/23/2023 8:46 AM, Daniel P. Berrangé wrote: > > On Thu, Oct 19, 2023 at 01:47:44PM -0700, Steve Sistare wrote: > >> Extend the blocker interface so that a blocker can be registered for > >> one or more migration modes. The existing interfaces register a > >> blocker for all modes, and the new interfaces take a varargs list > >> of modes. > >> > >> Internally, maintain a separate blocker list per mode. The same Error > >> object may be added to multiple lists. When a block is deleted, it is > >> removed from every list, and the Error is freed. > > > > I'm not sure that assocating blockers with migration modes is > > the optimal way to model this. > > > > IIUC, some of the migration blockers exist because the feature > > relies on state that only exists on the current host. > > > > This isn't a problem with CPR since the migration is within > > the same host. At the time though, these blockers should > > likely be redundant for a normal migration that uses "localhost". > > > > We can't express the distinction between localhost-migrate > > and cross-host-migrate historically, but we should have done. > > This new patch largely enables that I think which is good. > > > > What I think this means is that we shouldn't tie blockers > > to modes, but rather have different types of blockers as > > a bit set > > > > enum MigrationBlockerType { > > MIGRATION_BLOCKER_LOCAL_HOST = (1 << 0), > > MIGRATION_BLOCKER_CROSS_HOST = (1 << 1), > > }; > > > > #define MIGRATION_BLOCKER_ALL 0xff > > > > > > Cpr would check for blockers with MIGRATION_BLOCKER_LOCAL_HOST > > set only. > > > > Normal migration within localhost only would similarly only > > check MIGRATION_BLOCKER_LOCAL_HOST > > > > Normal migration between arbitrary host would check for > > MIGRATION_BLOCKER_LOCAL_HOST and MIGRATION_BLOCKER_CROSS_HOST > > Or, we could define MIG_MODE_LOCAL to relax the blockers for local migrations. > The user would add mode explicitly to the migrate command, or we could > implicitly switch from normal mode to local mode if we infer that the src > and target are the same node. MIG_MODE_LOCAL and MIG_MODE_CPR_REBOOT would > relax the same blockers for now, but conceivably that could change. > > When I add cpr-exec mode, it will have its own mode-specific blockers. > But, in your scheme, it could map to a new MigrationBlockerType. Yes, there could be further types of blocker. Do you have an example of something that would be a CPR blocker only ? I was thinking that migration blockers have a functional classification which motivates their existance. The different migration modes are describing particular usage scenarios, and a given usage scenario will imply blockers for one or more functional reasons. > I do prefer mode as the way of specifying the type of migration. Sure, I didn't mean to suggest "mode" as an input to 'migrate' is bad. Just that I see migration blockers classification as being distinct from the 'mode'. So a user could specify 'mode' with 'migrate' and that ends up mapping to certain types of blocker. > The question is whether we map mode directly to blockers, or map mode > plus other criteria such as locality to MigrationBlockerType(s) which > map to blockers. > > One consideration is, how will the user specify the equivalent of only-migratable > on the command line? I was thinking of adding -only-migratable > in a future patch, but if additional criteria maps to blockers, then we need > additional options or syntax. I guess I could see wanting to use --only-migratable to express that I want a guest that can do a localhost-migration, and CPR, but don't care about cross-host-migration, which would point towards blocker types being exposed. 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 :|