From patchwork Thu Jan 12 16:43:55 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 13098378 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 98EE1C54EBC for ; Thu, 12 Jan 2023 16:45:22 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pG0gZ-0004CF-PL; Thu, 12 Jan 2023 11:44:15 -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 1pG0gV-0004Bg-8C for qemu-devel@nongnu.org; Thu, 12 Jan 2023 11:44:11 -0500 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 1pG0gT-0000cw-J7 for qemu-devel@nongnu.org; Thu, 12 Jan 2023 11:44:11 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1673541848; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=JuD+ydF57zYdJdsWwViUOHg05/IJZ6rpv+rPeAQxTOk=; b=HtjaTSu4edEydKlD7Ue473Zxuy8z5wcEx0LBTV8vZvnkLmVaiKAjBx7kUua8sWw4aQB0MK ciLLOYoilIOKsPa1yKZgc1Dnql1ZXGqZrpMfuPxpIM2dbXDoPLtgozesSO9EGPj1tPgIQZ N6Cknw4QFcZuluSBlLqADSW9AW2XA5A= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-301-0rzpsSO5MLWsLCli73E0Dw-1; Thu, 12 Jan 2023 11:44:06 -0500 X-MC-Unique: 0rzpsSO5MLWsLCli73E0Dw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 5239F380670E for ; Thu, 12 Jan 2023 16:44:06 +0000 (UTC) Received: from t480s.fritz.box (unknown [10.39.193.30]) by smtp.corp.redhat.com (Postfix) with ESMTP id 710A24078903; Thu, 12 Jan 2023 16:44:04 +0000 (UTC) From: David Hildenbrand To: qemu-devel@nongnu.org Cc: David Hildenbrand , "Dr . David Alan Gilbert" , Juan Quintela , Peter Xu , "Michael S . Tsirkin" , Michal Privoznik Subject: [PATCH v3 0/8] virtio-mem: Handle preallocation with migration Date: Thu, 12 Jan 2023 17:43:55 +0100 Message-Id: <20230112164403.105085-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Received-SPF: pass client-ip=170.10.129.124; envelope-from=david@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_H2=-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 While playing with migration of virtio-mem with an ordinary file backing, I realized that migration and prealloc doesn't currently work as expected for virtio-mem. Further, Jing Qi reported that setup issues (insufficient huge pages on the destination) result in QEMU getting killed with SIGBUS instead of failing gracefully. In contrast to ordinary memory backend preallocation, virtio-mem preallocates memory before plugging blocks to the guest. Consequently, when migrating we are not actually preallocating on the destination but "only" migrate pages. Fix that be migrating the bitmap early, before any RAM content, and use that information to preallocate memory early, before migrating any RAM. Postcopy needs some extra care, and I realized that prealloc+postcopy is shaky in general. Let's at least try to mimic what ordinary prealloc+postcopy does: temporarily allocate the memory, discard it, and cross fingers that we'll still have sufficient memory when postcopy actually tries placing pages. Cc: Dr. David Alan Gilbert Cc: Juan Quintela Cc: Peter Xu Cc: Michael S. Tsirkin Cc: Michal Privoznik v3 -> v4: - First 3 patches: -- Minimze code changes and simplify -- Save immutable device state during qemu_savevm_state_setup() -- Don't use vmsd priorities, use a new flag -- Split it logically up - "migration/ram: Factor out check for advised postcopy" -- Don't factor out postcopy_is_running() - "virtio-mem: Migrate immutable properties early" -- Adjust to changed vmsd interface - "virtio-mem: Proper support for preallocation with migration" -- Drop sanity check in virtio_mem_post_load_early() v2 -> v3: - New approach/rewrite, drop RB and TB of last patch v1 -> v2: - Added RBs and Tested-bys - "virtio-mem: Fail if a memory backend with "prealloc=on" is specified" -- Fail instead of warn -- Adjust subject/description David Hildenbrand (8): migration/savevm: Move more savevm handling into vmstate_save() migration/savevm: Prepare vmdesc json writer in qemu_savevm_state_setup() migration/savevm: Allow immutable device state to be migrated early (i.e., before RAM) migration/vmstate: Introduce VMSTATE_WITH_TMP_TEST() and VMSTATE_BITMAP_TEST() migration/ram: Factor out check for advised postcopy virtio-mem: Fail if a memory backend with "prealloc=on" is specified virtio-mem: Migrate immutable properties early virtio-mem: Proper support for preallocation with migration hw/core/machine.c | 4 +- hw/virtio/virtio-mem.c | 144 ++++++++++++++++++++++++++++++++- include/hw/virtio/virtio-mem.h | 8 ++ include/migration/misc.h | 4 +- include/migration/vmstate.h | 17 +++- migration/migration.c | 11 +++ migration/migration.h | 4 + migration/ram.c | 8 +- migration/savevm.c | 105 +++++++++++++----------- 9 files changed, 247 insertions(+), 58 deletions(-)