From nobody Sat Apr 12 15:38:54 2025 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1694418712555980.1904435777265; Mon, 11 Sep 2023 00:51:52 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qfbh8-0004Ox-Mw; Mon, 11 Sep 2023 03:50:54 -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 1qfbgy-00047y-5F for qemu-devel@nongnu.org; Mon, 11 Sep 2023 03:50:45 -0400 Received: from gandalf.ozlabs.org ([150.107.74.76]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qfbgv-0008Ej-Sh for qemu-devel@nongnu.org; Mon, 11 Sep 2023 03:50:43 -0400 Received: from gandalf.ozlabs.org (gandalf.ozlabs.org [150.107.74.76]) by gandalf.ozlabs.org (Postfix) with ESMTP id 4Rkf5r4dzjz4xNG; Mon, 11 Sep 2023 17:50:40 +1000 (AEST) Received: from authenticated.ozlabs.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 mail.ozlabs.org (Postfix) with ESMTPSA id 4Rkf5p6JKtz4xM5; Mon, 11 Sep 2023 17:50:38 +1000 (AEST) From: =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= To: qemu-devel@nongnu.org Cc: Alex Williamson , Avihai Horon , Peter Xu , =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= Subject: [PULL 12/13] vfio/migration: Block VFIO migration with background snapshot Date: Mon, 11 Sep 2023 09:50:07 +0200 Message-ID: <20230911075008.462712-13-clg@redhat.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230911075008.462712-1-clg@redhat.com> References: <20230911075008.462712-1-clg@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=150.107.74.76; envelope-from=SRS0=GLJ6=E3=redhat.com=clg@ozlabs.org; helo=gandalf.ozlabs.org X-Spam_score_int: -16 X-Spam_score: -1.7 X-Spam_bar: - X-Spam_report: (-1.7 / 5.0 requ) BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.249, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no 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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZM-MESSAGEID: 1694418714377100001 From: Avihai Horon Background snapshot allows creating a snapshot of the VM while it's running and keeping it small by not including dirty RAM pages. The way it works is by first stopping the VM, saving the non-iterable devices' state and then starting the VM and saving the RAM while write protecting it with UFFD. The resulting snapshot represents the VM state at snapshot start. VFIO migration is not compatible with background snapshot. First of all, VFIO device state is not even saved in background snapshot because only non-iterable device state is saved. But even if it was saved, after starting the VM, a VFIO device could dirty pages without it being detected by UFFD write protection. This would corrupt the snapshot, as the RAM in it would not represent the RAM at snapshot start. To prevent this, block VFIO migration with background snapshot. Signed-off-by: Avihai Horon Reviewed-by: Peter Xu Signed-off-by: C=C3=A9dric Le Goater --- hw/vfio/migration.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c index 20994dc1d60b1606728415fec17c19cfd00c4dee..da43dcd2fe0734091960e3eb2ff= a26750073be72 100644 --- a/hw/vfio/migration.c +++ b/hw/vfio/migration.c @@ -340,7 +340,8 @@ static int vfio_save_prepare(void *opaque, Error **errp) VFIODevice *vbasedev =3D opaque; =20 /* - * Snapshot doesn't use postcopy, so allow snapshot even if postcopy i= s on. + * Snapshot doesn't use postcopy nor background snapshot, so allow sna= pshot + * even if they are on. */ if (runstate_check(RUN_STATE_SAVE_VM)) { return 0; @@ -353,6 +354,14 @@ static int vfio_save_prepare(void *opaque, Error **err= p) return -EOPNOTSUPP; } =20 + if (migrate_background_snapshot()) { + error_setg( + errp, + "%s: VFIO migration is not supported with background snapshot", + vbasedev->name); + return -EOPNOTSUPP; + } + return 0; } =20 --=20 2.41.0