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=-7.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URG_BIZ,URIBL_BLOCKED,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 2DA47C35646 for ; Fri, 21 Feb 2020 15:17:00 +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 EAB9B206EF for ; Fri, 21 Feb 2020 15:16:59 +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="N7w9eJSa" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EAB9B206EF 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]:59562 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j5A31-0006F7-2T for qemu-devel@archiver.kernel.org; Fri, 21 Feb 2020 10:16:59 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:60872) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j5A1I-00052f-E9 for qemu-devel@nongnu.org; Fri, 21 Feb 2020 10:15:14 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1j5A1F-0000UV-OA for qemu-devel@nongnu.org; Fri, 21 Feb 2020 10:15:11 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:47927 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 1j5A1F-0000Te-J0 for qemu-devel@nongnu.org; Fri, 21 Feb 2020 10:15:09 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1582298108; 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=uTG4/15rK4FE9jhreYjIh+knHd/iEu3xJyJAukuG+Q4=; b=N7w9eJSajUgWaoe0wW8p4H+z7AhedTj7WhosDTALNcCTtzbi1xaB6W+Bq+yDcuMgR97bUN JqPun0YBQzTAu4AwdG2kUc42pu1aCT9Y167YNaa3gnJZU8SF28FYkZrPM5wJKsL6cH3OH0 X452HjzPEEgebkop/imiIqoTwcmAo9I= 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-107-zYzEfPX9NjG5jDXE6TyJ4A-1; Fri, 21 Feb 2020 10:15:05 -0500 X-MC-Unique: zYzEfPX9NjG5jDXE6TyJ4A-1 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 2784094DF3; Fri, 21 Feb 2020 15:15:00 +0000 (UTC) Received: from work-vm (unknown [10.36.118.1]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3CA996E3EE; Fri, 21 Feb 2020 15:14:49 +0000 (UTC) Date: Fri, 21 Feb 2020 15:14:47 +0000 From: "Dr. David Alan Gilbert" To: David Hildenbrand Subject: Re: [PATCH v1 05/13] migrate/ram: Handle RAM block resizes during precopy Message-ID: <20200221151447.GF2931@work-vm> References: <20200219161725.115218-1-david@redhat.com> <20200219161725.115218-6-david@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200219161725.115218-6-david@redhat.com> User-Agent: Mutt/1.13.3 (2020-01-12) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 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 , Juan Quintela , "Michael S. Tsirkin" , Richard Henderson , qemu-devel@nongnu.org, Peter Xu , Shannon Zhao , Igor Mammedov , Paolo Bonzini , Alex =?iso-8859-1?Q?Benn=E9e?= , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * David Hildenbrand (david@redhat.com) wrote: > Resizing while migrating is dangerous and does not work as expected. > The whole migration code works on the usable_length of ram blocks and doe= s > not expect this to change at random points in time. >=20 > In the case of precopy, the ram block size must not change on the source, > after syncing the RAM block list in ram_save_setup(), so as long as the > guest is still running on the source. >=20 > Resizing can be trigger *after* (but not during) a reset in > ACPI code by the guest > - hw/arm/virt-acpi-build.c:acpi_ram_update() > - hw/i386/acpi-build.c:acpi_ram_update() >=20 > Use the ram block notifier to get notified about resizes. Let's simply > cancel migration and indicate the reason. We'll continue running on the > source. No harm done. >=20 > Update the documentation. Postcopy will be handled separately. >=20 > Cc: "Dr. David Alan Gilbert" > Cc: Juan Quintela > Cc: Eduardo Habkost > Cc: Paolo Bonzini > Cc: Igor Mammedov > Cc: "Michael S. Tsirkin" > Cc: Richard Henderson > Cc: Shannon Zhao > Cc: Alex Benn=E9e > Cc: Peter Xu > Signed-off-by: David Hildenbrand > --- > exec.c | 5 +++-- > include/exec/memory.h | 10 ++++++---- > migration/migration.c | 9 +++++++-- > migration/migration.h | 1 + > migration/ram.c | 41 +++++++++++++++++++++++++++++++++++++++++ > 5 files changed, 58 insertions(+), 8 deletions(-) >=20 > diff --git a/exec.c b/exec.c > index b75250e773..8b015821d6 100644 > --- a/exec.c > +++ b/exec.c > @@ -2120,8 +2120,9 @@ static int memory_try_enable_merging(void *addr, si= ze_t len) > return qemu_madvise(addr, len, QEMU_MADV_MERGEABLE); > } > =20 > -/* Only legal before guest might have detected the memory size: e.g. on > - * incoming migration, or right after reset. > +/* > + * Resizing RAM while migrating can result in the migration being cancel= ed. > + * Care has to be taken if the guest might have already detected the mem= ory. > * > * As memory core doesn't know how is memory accessed, it is up to > * resize callback to update device state and/or add assertions to detec= t > diff --git a/include/exec/memory.h b/include/exec/memory.h > index e85b7de99a..de111347e8 100644 > --- a/include/exec/memory.h > +++ b/include/exec/memory.h > @@ -113,7 +113,7 @@ typedef struct IOMMUNotifier IOMMUNotifier; > #define RAM_SHARED (1 << 1) > =20 > /* Only a portion of RAM (used_length) is actually used, and migrated. > - * This used_length size can change across reboots. > + * Resizing RAM while migrating can result in the migration being cancel= ed. > */ > #define RAM_RESIZEABLE (1 << 2) > =20 > @@ -843,7 +843,9 @@ void memory_region_init_ram_shared_nomigrate(MemoryRe= gion *mr, > * RAM. Accesses into the region wi= ll > * modify memory directly. Only an = initial > * portion of this RAM is actually u= sed. > - * The used size can change across r= eboots. > + * Changing the size while migrating > + * can result in the migration being > + * canceled. > * > * @mr: the #MemoryRegion to be initialized. > * @owner: the object that tracks the region's reference count > @@ -1464,8 +1466,8 @@ void *memory_region_get_ram_ptr(MemoryRegion *mr); > =20 > /* memory_region_ram_resize: Resize a RAM region. > * > - * Only legal before guest might have detected the memory size: e.g. on > - * incoming migration, or right after reset. > + * Resizing RAM while migrating can result in the migration being cancel= ed. > + * Care has to be taken if the guest might have already detected the mem= ory. > * > * @mr: a memory region created with @memory_region_init_resizeable_ram. > * @newsize: the new size the region > diff --git a/migration/migration.c b/migration/migration.c > index 8fb68795dc..ac9751dbe5 100644 > --- a/migration/migration.c > +++ b/migration/migration.c > @@ -175,13 +175,18 @@ void migration_object_init(void) > } > } > =20 > +void migration_cancel(void) > +{ > + migrate_fd_cancel(current_migration); > +} > + > void migration_shutdown(void) > { > /* > * Cancel the current migration - that will (eventually) > * stop the migration using this structure > */ > - migrate_fd_cancel(current_migration); > + migration_cancel(); > object_unref(OBJECT(current_migration)); > } > =20 > @@ -2019,7 +2024,7 @@ void qmp_migrate(const char *uri, bool has_blk, boo= l blk, > =20 > void qmp_migrate_cancel(Error **errp) > { > - migrate_fd_cancel(migrate_get_current()); > + migration_cancel(); > } > =20 > void qmp_migrate_continue(MigrationStatus state, Error **errp) > diff --git a/migration/migration.h b/migration/migration.h > index 8473ddfc88..79fd74afa5 100644 > --- a/migration/migration.h > +++ b/migration/migration.h > @@ -343,5 +343,6 @@ int foreach_not_ignored_block(RAMBlockIterFunc func, = void *opaque); > void migration_make_urgent_request(void); > void migration_consume_urgent_request(void); > bool migration_rate_limit(void); > +void migration_cancel(void); > =20 > #endif > diff --git a/migration/ram.c b/migration/ram.c > index ed23ed1c7c..57f32011a3 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 +3711,48 @@ 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_size) > +{ > + ram_addr_t offset; > + Error *err =3D NULL; > + RAMBlock *rb =3D qemu_ram_block_from_host(host, false, &offset); > + > + if (ramblock_is_ignored(rb)) { > + return; > + } > + > + /* > + * Some resizes are triggered on the migration target by precopy cod= e, > + * when synchronizing RAM block sizes. In these cases, the VM is not > + * running and migration is not idle. We have to ignore these resize= s, > + * as we only care about resizes during precopy on the migration sou= rce. > + * This handler is always registered, so ignore when migration is id= le. > + */ > + if (migration_is_idle() || !runstate_is_running() || > + postcopy_is_running()) { > + return; > + } > + > + /* > + * Precopy code cannot deal with the size of ram blocks changing 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 block '%s' resized during precopy.", rb->idstr= ); > + migrate_set_error(migrate_get_current(), err); > + error_free(err); > + migration_cancel(); > +} > + > +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_state); > + ram_block_notifier_add(&ram_mig_ram_notifier); Can we avoid the question of the 'is_idle' checks by doing this registration in save_setup/load_setup and unregistering in save_cleanup/load_cleanup? That means if we land in the handler we know we're in either an incoming or outgoing migration and then you just have to check which? Dave > } > --=20 > 2.24.1 >=20 -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK