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 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 F2DDBC433EF for ; Tue, 5 Jul 2022 20:37:06 +0000 (UTC) Received: from localhost ([::1]:56560 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1o8pI9-0005MF-HJ for qemu-devel@archiver.kernel.org; Tue, 05 Jul 2022 16:37:05 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:59878) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1o8pHL-0004fW-LZ for qemu-devel@nongnu.org; Tue, 05 Jul 2022 16:36:15 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:11114 helo=mx0a-001b2d01.pphosted.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1o8pHI-0004XA-Q5 for qemu-devel@nongnu.org; Tue, 05 Jul 2022 16:36:15 -0400 Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 265JXHjL013672; Tue, 5 Jul 2022 20:36:07 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=from : to : cc : subject : date : message-id : content-transfer-encoding : mime-version; s=pp1; bh=wcA7qyUt6TFr52EqZ2LwShkFgWhZ0H7tJTyO/lP36fI=; b=NFw/cGYi2w8frAqCJB5Dgjy6NHoIiuvib/2Wjgw6I2xOuhbOT5sCh4aOZ0z6ow3uNYMs y/AY2IrOT8dgYtdVQ1V6EAsbco18UMLalNXAFUSkB2u/Y6EJRJJuW2XZJCz99n08xd3D IHjJUJic2AIizS5a3/abhWBfCr6TGD73vVCdxS78vDvybWhim+1kIzn4FVZG57Yargdl tlgIVASC4n3d9mbkrWQqXSP9PnY8l70tctL2Jyx64mHDq8QX8HiWjQxsGNivsbtyt5Qm uXR+iO/oJdXyhBYvy9//JnxFD67dDo58g3DKqqi+aUMjPYPUgJJ9UHyltbaQ8Ql0V0d5 LQ== Received: from pps.reinject (localhost [127.0.0.1]) by mx0b-001b2d01.pphosted.com (PPS) with ESMTPS id 3h4ujd1fsc-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 05 Jul 2022 20:36:07 +0000 Received: from m0098416.ppops.net (m0098416.ppops.net [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 265Ka6D2006668; Tue, 5 Jul 2022 20:36:06 GMT Received: from ppma06fra.de.ibm.com (48.49.7a9f.ip4.static.sl-reverse.com [159.122.73.72]) by mx0b-001b2d01.pphosted.com (PPS) with ESMTPS id 3h4ujd1frj-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 05 Jul 2022 20:36:06 +0000 Received: from pps.filterd (ppma06fra.de.ibm.com [127.0.0.1]) by ppma06fra.de.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 265KL7Wd032185; Tue, 5 Jul 2022 20:36:05 GMT Received: from b06cxnps4074.portsmouth.uk.ibm.com (d06relay11.portsmouth.uk.ibm.com [9.149.109.196]) by ppma06fra.de.ibm.com with ESMTP id 3h4ucy818r-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 05 Jul 2022 20:36:04 +0000 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 265Ka1Vb21692698 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 5 Jul 2022 20:36:01 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 52F5D11C050; Tue, 5 Jul 2022 20:36:01 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id F1D8211C04A; Tue, 5 Jul 2022 20:36:00 +0000 (GMT) Received: from heavy.ibmuc.com (unknown [9.171.47.233]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 5 Jul 2022 20:36:00 +0000 (GMT) From: Ilya Leoshkevich To: Juan Quintela , "Dr. David Alan Gilbert" Cc: qemu-devel@nongnu.org, Christian Borntraeger , Peter Maydell , Ilya Leoshkevich Subject: [PATCH v3] multifd: Copy pages before compressing them with zlib Date: Tue, 5 Jul 2022 22:35:59 +0200 Message-Id: <20220705203559.2960949-1-iii@linux.ibm.com> X-Mailer: git-send-email 2.35.3 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: mZr2pqyNhI1h1OX9t7Zt2xhktCdcnyde X-Proofpoint-GUID: RcS0hyHCuq_vf0OSwvZGU5bVbNzw6TPS Content-Transfer-Encoding: 8bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.883,Hydra:6.0.517,FMLib:17.11.122.1 definitions=2022-07-05_18,2022-06-28_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 bulkscore=0 lowpriorityscore=0 spamscore=0 priorityscore=1501 mlxscore=0 suspectscore=0 phishscore=0 clxscore=1015 malwarescore=0 impostorscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2206140000 definitions=main-2207050088 Received-SPF: pass client-ip=148.163.158.5; envelope-from=iii@linux.ibm.com; helo=mx0a-001b2d01.pphosted.com X-Spam_score_int: -19 X-Spam_score: -2.0 X-Spam_bar: -- X-Spam_report: (-2.0 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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" zlib_send_prepare() compresses pages of a running VM. zlib does not make any thread-safety guarantees with respect to changing deflate() input concurrently with deflate() [1]. One can observe problems due to this with the IBM zEnterprise Data Compression accelerator capable zlib [2]. When the hardware acceleration is enabled, migration/multifd/tcp/plain/zlib test fails intermittently [3] due to sliding window corruption. The accelerator's architecture explicitly discourages concurrent accesses [4]: Page 26-57, "Other Conditions": As observed by this CPU, other CPUs, and channel programs, references to the parameter block, first, second, and third operands may be multiple-access references, accesses to these storage locations are not necessarily block-concurrent, and the sequence of these accesses or references is undefined. Mark Adler pointed out that vanilla zlib performs double fetches under certain circumstances as well [5], therefore we need to copy data before passing it to deflate(). [1] https://zlib.net/manual.html [2] https://github.com/madler/zlib/pull/410 [3] https://lists.nongnu.org/archive/html/qemu-devel/2022-03/msg03988.html [4] http://publibfp.dhe.ibm.com/epubs/pdf/a227832c.pdf [5] https://lists.gnu.org/archive/html/qemu-devel/2022-07/msg00889.html Signed-off-by: Ilya Leoshkevich --- v1: https://lists.gnu.org/archive/html/qemu-devel/2022-03/msg06841.html v1 -> v2: Rebase, mention Mark Adler's reply in the commit message. v2: https://lists.gnu.org/archive/html/qemu-devel/2022-07/msg00627.html v2 -> v3: Get rid of pointer maths (David). Use a more relevant link to Mark Adler's comment (Peter). migration/multifd-zlib.c | 38 ++++++++++++++++++++++++++++++-------- 1 file changed, 30 insertions(+), 8 deletions(-) diff --git a/migration/multifd-zlib.c b/migration/multifd-zlib.c index 3a7ae44485..18213a9513 100644 --- a/migration/multifd-zlib.c +++ b/migration/multifd-zlib.c @@ -27,6 +27,8 @@ struct zlib_data { uint8_t *zbuff; /* size of compressed buffer */ uint32_t zbuff_len; + /* uncompressed buffer of size qemu_target_page_size() */ + uint8_t *buf; }; /* Multifd zlib compression */ @@ -45,26 +47,38 @@ static int zlib_send_setup(MultiFDSendParams *p, Error **errp) { struct zlib_data *z = g_new0(struct zlib_data, 1); z_stream *zs = &z->zs; + const char *err_msg; zs->zalloc = Z_NULL; zs->zfree = Z_NULL; zs->opaque = Z_NULL; if (deflateInit(zs, migrate_multifd_zlib_level()) != Z_OK) { - g_free(z); - error_setg(errp, "multifd %u: deflate init failed", p->id); - return -1; + err_msg = "deflate init failed"; + goto err_free_z; } /* This is the maxium size of the compressed buffer */ z->zbuff_len = compressBound(MULTIFD_PACKET_SIZE); z->zbuff = g_try_malloc(z->zbuff_len); if (!z->zbuff) { - deflateEnd(&z->zs); - g_free(z); - error_setg(errp, "multifd %u: out of memory for zbuff", p->id); - return -1; + err_msg = "out of memory for zbuff"; + goto err_deflate_end; + } + z->buf = g_try_malloc(qemu_target_page_size()); + if (!z->buf) { + err_msg = "out of memory for buf"; + goto err_free_zbuff; } p->data = z; return 0; + +err_free_zbuff: + g_free(z->zbuff); +err_deflate_end: + deflateEnd(&z->zs); +err_free_z: + g_free(z); + error_setg(errp, "multifd %u: %s", p->id, err_msg); + return -1; } /** @@ -82,6 +96,8 @@ static void zlib_send_cleanup(MultiFDSendParams *p, Error **errp) deflateEnd(&z->zs); g_free(z->zbuff); z->zbuff = NULL; + g_free(z->buf); + z->buf = NULL; g_free(p->data); p->data = NULL; } @@ -114,8 +130,14 @@ static int zlib_send_prepare(MultiFDSendParams *p, Error **errp) flush = Z_SYNC_FLUSH; } + /* + * Since the VM might be running, the page may be changing concurrently + * with compression. zlib does not guarantee that this is safe, + * therefore copy the page before calling deflate(). + */ + memcpy(z->buf, p->pages->block->host + p->normal[i], page_size); zs->avail_in = page_size; - zs->next_in = p->pages->block->host + p->normal[i]; + zs->next_in = z->buf; zs->avail_out = available; zs->next_out = z->zbuff + out_size; -- 2.35.3