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=-6.6 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 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 4E3D6C4BA13 for ; Wed, 26 Feb 2020 15:58:33 +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 1B40D2467B for ; Wed, 26 Feb 2020 15:58:32 +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="dmTUIhqj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1B40D2467B 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]:46268 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j6z4y-0002QF-4r for qemu-devel@archiver.kernel.org; Wed, 26 Feb 2020 10:58:32 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:34149) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j6z0g-0003OP-Jh for qemu-devel@nongnu.org; Wed, 26 Feb 2020 10:54:08 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1j6z0f-00036Q-4R for qemu-devel@nongnu.org; Wed, 26 Feb 2020 10:54:06 -0500 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:40110 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1j6z0f-00036E-0H for qemu-devel@nongnu.org; Wed, 26 Feb 2020 10:54:05 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1582732444; 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=jMU92ageiju/KM9IcMJHHwrw+bCHKXRrCpa6R63pejE=; b=dmTUIhqjcjUwWuO1hSMsO08zDLH1aU+jw/C2n4eN8AjMfxnu7pmHE412BH8oJxmL21NBZj 7cYonWrtFNMDwtHdnEbkMRRFwboC1Ih0eJPbIN5tlbNc0/qW3o1ic7IXdvlzfZV3cUPJTA j9xrj95w1ofn03tSms0yBahcHVZpLO8= 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-289-N2FJ90KnPH-zi3hoxDSi9g-1; Wed, 26 Feb 2020 10:54:03 -0500 X-MC-Unique: N2FJ90KnPH-zi3hoxDSi9g-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 89B94107ACC4; Wed, 26 Feb 2020 15:54:01 +0000 (UTC) Received: from t480s.redhat.com (ovpn-117-196.ams2.redhat.com [10.36.117.196]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8C4651001B2C; Wed, 26 Feb 2020 15:53:56 +0000 (UTC) From: David Hildenbrand To: qemu-devel@nongnu.org Subject: [PATCH v3 10/13] migration/ram: Handle RAM block resizes during postcopy Date: Wed, 26 Feb 2020 16:53:01 +0100 Message-Id: <20200226155304.60219-11-david@redhat.com> In-Reply-To: <20200226155304.60219-1-david@redhat.com> References: <20200226155304.60219-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 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 , David Hildenbrand , Richard Henderson , "Dr . David Alan Gilbert" , Peter Xu , "Michael S. Tsirkin" , Shannon Zhao , Igor Mammedov , Paolo Bonzini , =?UTF-8?q?Alex=20Benn=C3=A9e?= , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Resizing while migrating is dangerous and does not work as expected. The whole migration code works on the usable_length of ram blocks and does not expect this to change at random points in time. In the case of postcopy, relying on used_length is racy as soon as the guest is running. Also, when used_length changes we might leave the uffd handler registered for some memory regions, reject valid pages when migrating and fail when sending the recv bitmap to the source. 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() Let's remember the original used_length in a separate variable and use it in relevant postcopy code. Make sure to update it when we resize during precopy, when synchronizing the RAM block sizes with the source. Reviewed-by: Peter Xu 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=C3=A9e Cc: Peter Xu Signed-off-by: David Hildenbrand --- include/exec/ramblock.h | 10 ++++++++++ migration/postcopy-ram.c | 15 ++++++++++++--- migration/ram.c | 11 +++++++++-- 3 files changed, 31 insertions(+), 5 deletions(-) diff --git a/include/exec/ramblock.h b/include/exec/ramblock.h index 07d50864d8..664701b759 100644 --- a/include/exec/ramblock.h +++ b/include/exec/ramblock.h @@ -59,6 +59,16 @@ struct RAMBlock { */ unsigned long *clear_bmap; uint8_t clear_bmap_shift; + + /* + * RAM block length that corresponds to the used_length on the migrati= on + * source (after RAM block sizes were synchronized). Especially, after + * starting to run the guest, used_length and postcopy_length can diff= er. + * Used to register/unregister uffd handlers and as the size of the re= ceived + * bitmap. Receiving any page beyond this length will bail out, as it + * could not have been valid on the source. + */ + ram_addr_t postcopy_length; }; #endif #endif diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c index a36402722b..c68caf4e42 100644 --- a/migration/postcopy-ram.c +++ b/migration/postcopy-ram.c @@ -17,6 +17,7 @@ */ =20 #include "qemu/osdep.h" +#include "qemu/rcu.h" #include "exec/target_page.h" #include "migration.h" #include "qemu-file.h" @@ -31,6 +32,7 @@ #include "qemu/error-report.h" #include "trace.h" #include "hw/boards.h" +#include "exec/ramblock.h" =20 /* Arbitrary limit on size of each discard command, * keeps them around ~200 bytes @@ -456,6 +458,13 @@ static int init_range(RAMBlock *rb, void *opaque) ram_addr_t length =3D qemu_ram_get_used_length(rb); trace_postcopy_init_range(block_name, host_addr, offset, length); =20 + /* + * Save the used_length before running the guest. In case we have to + * resize RAM blocks when syncing RAM block sizes from the source duri= ng + * precopy, we'll update it manually via the ram block notifier. + */ + rb->postcopy_length =3D length; + /* * We need the whole of RAM to be truly empty for postcopy, so things * like ROMs and any data tables built during init must be zero'd @@ -478,7 +487,7 @@ static int cleanup_range(RAMBlock *rb, void *opaque) const char *block_name =3D qemu_ram_get_idstr(rb); void *host_addr =3D qemu_ram_get_host_addr(rb); ram_addr_t offset =3D qemu_ram_get_offset(rb); - ram_addr_t length =3D qemu_ram_get_used_length(rb); + ram_addr_t length =3D rb->postcopy_length; MigrationIncomingState *mis =3D opaque; struct uffdio_range range_struct; trace_postcopy_cleanup_range(block_name, host_addr, offset, length); @@ -600,7 +609,7 @@ static int nhp_range(RAMBlock *rb, void *opaque) const char *block_name =3D qemu_ram_get_idstr(rb); void *host_addr =3D qemu_ram_get_host_addr(rb); ram_addr_t offset =3D qemu_ram_get_offset(rb); - ram_addr_t length =3D qemu_ram_get_used_length(rb); + ram_addr_t length =3D rb->postcopy_length; trace_postcopy_nhp_range(block_name, host_addr, offset, length); =20 /* @@ -644,7 +653,7 @@ static int ram_block_enable_notify(RAMBlock *rb, void *= opaque) struct uffdio_register reg_struct; =20 reg_struct.range.start =3D (uintptr_t)qemu_ram_get_host_addr(rb); - reg_struct.range.len =3D qemu_ram_get_used_length(rb); + reg_struct.range.len =3D rb->postcopy_length; reg_struct.mode =3D UFFDIO_REGISTER_MODE_MISSING; =20 /* Now tell our userfault_fd that it's responsible for this area */ diff --git a/migration/ram.c b/migration/ram.c index 1a5ff07997..ee5c3d5784 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -244,7 +244,7 @@ int64_t ramblock_recv_bitmap_send(QEMUFile *file, return -1; } =20 - nbits =3D block->used_length >> TARGET_PAGE_BITS; + nbits =3D block->postcopy_length >> TARGET_PAGE_BITS; =20 /* * Make sure the tmp bitmap buffer is big enough, e.g., on 32bit @@ -3160,7 +3160,13 @@ static int ram_load_postcopy(QEMUFile *f) break; } =20 - if (!offset_in_ramblock(block, addr)) { + /* + * Relying on used_length is racy and can result in false posi= tives. + * We might place pages beyond used_length in case RAM was shr= unk + * while in postcopy, which is fine - trying to place via + * UFFDIO_COPY/UFFDIO_ZEROPAGE will never segfault. + */ + if (!block->host || addr >=3D block->postcopy_length) { error_report("Illegal RAM offset " RAM_ADDR_FMT, addr); ret =3D -EINVAL; break; @@ -3757,6 +3763,7 @@ static void ram_mig_ram_block_resized(RAMBlockNotifie= r *n, void *host, rb->idstr); } } + rb->postcopy_length =3D new_size; break; case POSTCOPY_INCOMING_NONE: case POSTCOPY_INCOMING_RUNNING: --=20 2.24.1