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 X-Spam-Level: X-Spam-Status: No, score=-5.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 05A13C2BA83 for ; Fri, 14 Feb 2020 15:15:50 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id C53A02465D for ; Fri, 14 Feb 2020 15:15:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="cHhYHvjy" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C53A02465D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:40082 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j2ch2-0005ob-U7 for qemu-devel@archiver.kernel.org; Fri, 14 Feb 2020 10:15:48 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:45937) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j2cgM-0005Kl-0H for qemu-devel@nongnu.org; Fri, 14 Feb 2020 10:15:07 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1j2cgK-00036j-NY for qemu-devel@nongnu.org; Fri, 14 Feb 2020 10:15:05 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:35035 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1j2cgK-00035D-JP for qemu-devel@nongnu.org; Fri, 14 Feb 2020 10:15:04 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1581693303; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=aS1PTaXFbNpyQStsTenstqpl8hqHDWaeVDu9BEVRlac=; b=cHhYHvjyV2jxqU4yq57CyxnnNwOaUx4zhl4iKT9RcgYk8k4fEiLaBRC1SKkPhK0B8JXjXO Dt/lZ6kOXOGrAJW8YhcN1r8zCFP3M4TvtaTLXVFHttPPMHCddJvmxnUQKNUKys2q4pu36J TXceqGxUylsMlcCizVGdYQMw2uDHuMc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-4-C-zw-bI8PKSRuOWHSJe7JQ-1; Fri, 14 Feb 2020 10:15:01 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D87F7800D4E; Fri, 14 Feb 2020 15:14:59 +0000 (UTC) Received: from work-vm (unknown [10.36.118.141]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 09D6217DC8; Fri, 14 Feb 2020 15:14:52 +0000 (UTC) Date: Fri, 14 Feb 2020 15:14:50 +0000 From: "Dr. David Alan Gilbert" To: David Hildenbrand Subject: Re: [PATCH RFC] memory: Don't allow to resize RAM while migrating Message-ID: <20200214151450.GI3283@work-vm> References: <20200213172016.196609-1-david@redhat.com> <20200214102514.GB3283@work-vm> <30a66b1d-184e-a684-d0d2-c3921366b478@redhat.com> <20200214104230.GC3283@work-vm> <20200214110226.GD3283@work-vm> <9a15fd0e-77d1-b3a0-4824-665f85f79c71@redhat.com> <87k14pgwud.fsf@secure.laptop> <60ddcc66-2744-c131-f876-5a7e27a04ba8@redhat.com> MIME-Version: 1.0 In-Reply-To: <60ddcc66-2744-c131-f876-5a7e27a04ba8@redhat.com> User-Agent: Mutt/1.13.3 (2020-01-12) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-MC-Unique: C-zw-bI8PKSRuOWHSJe7JQ-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Eduardo Habkost , "Michael S. Tsirkin" , quintela@redhat.com, Richard Henderson , qemu-devel@nongnu.org, Shameerali Kolothum Thodi , Shannon Zhao , Igor Mammedov , Paolo Bonzini , Alex =?iso-8859-1?Q?Benn=E9e?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * David Hildenbrand (david@redhat.com) wrote: >=20 > >> diff --git a/migration/ram.c b/migration/ram.c > >> index ed23ed1c7c..f86f32b453 100644 > >> --- a/migration/ram.c > >> +++ b/migration/ram.c > >> @@ -52,6 +52,7 @@ > >> #include "migration/colo.h" > >> #include "block.h" > >> #include "sysemu/sysemu.h" > >> +#include "sysemu/runstate.h" > >> #include "savevm.h" > >> #include "qemu/iov.h" > >> #include "multifd.h" > >> @@ -3710,8 +3711,49 @@ static SaveVMHandlers savevm_ram_handlers =3D { > >> .resume_prepare =3D ram_resume_prepare, > >> }; > >> =20 > >> +static void ram_mig_ram_block_resized(RAMBlockNotifier *n, void *host= , > >> + size_t old_size, size_t new_siz= e) > >> +{ > >> + /* > >> + * We don't care about resizes triggered on incoming migration (w= hen > >> + * syncing ram blocks), or of course, when no migration is going = on. > >> + */ > >> + if (migration_is_idle() || !runstate_is_running()) { > >> + return; > >> + } > >> + > >> + if (!postcopy_is_running()) { > >> + Error *err =3D NULL; > >> + > >> + /* > >> + * Precopy code cannot deal with the size of ram blocks chang= ing at > >> + * random points in time. We're still running on the source, = abort > >> + * the migration and continue running here. Make sure to wait= until > >> + * migration was canceled. > >> + */ > >> + error_setg(&err, "RAM resized during precopy."); > >> + migrate_set_error(migrate_get_current(), err); > >> + error_free(err); > >> + migration_cancel(); > >=20 > > If we can't do anything else, this is reasonable. > >=20 > > But as discussed before, it is still not fully clear to me _why_ are > > ramblocks changing if we have disabled add/remove memory during migrati= on. >=20 >=20 > Ramblock add/remove is ties to device add/remove, which we block. >=20 > Resize, however, it not. Here, the resize happens while the guest is > booting up. The content/size of the ram block depends also on previous > guest action AFAIK. There is no way from stopping the guest from doing > that. It's required for the guest to continue booting (with ACPI). >=20 > I'm currently working on a project which reuses resizable ram blocks in > different context. There, I can simply defer/avoid resizing when > migration is active. In the ACPI case, however, we cannot avoid it. >=20 > Hope that answers your question >=20 > >=20 > >> + } else { > >> + /* > >> + * Postcopy code cannot deal with the size of ram blocks chan= ging at > >> + * random points in time. We're running on the target. Fail h= ard. > >> + * > >> + * TODO: How to handle this in a better way? > >> + */ > >> + error_report("RAM resized during postcopy."); > >> + exit(-1); > >=20 > > Idea is good, but we also need to exit destination, not only source, no= ? >=20 > @Dave, any idea what could be the right thing to do here? I think that's OK; postcopy_is_running() will return true on the destination (e.g. see it's use in ram_load()) and should work. I'd really appreciate if you could print hte RAMBlock or something at this point - when we hit this error we're going to want to try and figure out why. Dave > >=20 > >> + } > >> +} > >=20 > >=20 > >=20 > >> +static RAMBlockNotifier ram_mig_ram_notifier =3D { > >> + .ram_block_resized =3D ram_mig_ram_block_resized, > >> +}; > >> + > >> void ram_mig_init(void) > >> { > >> qemu_mutex_init(&XBZRLE.lock); > >> register_savevm_live("ram", 0, 4, &savevm_ram_handlers, &ram_stat= e); > >> + ram_block_notifier_add(&ram_mig_ram_notifier); > >> } > >=20 > > Shouldn't we remove the notifier when we finish the migration. >=20 > It's called from main() unconditionally (so not when migration starts), > so the notifier remains active the whole QEMU lifetime (which should be > fine AFAIKT). >=20 > --=20 > Thanks, >=20 > David / dhildenb -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK