From patchwork Sun Jul 12 10:00:34 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Claudio Fontana X-Patchwork-Id: 278029 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=-8.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 2F2E6C433E1 for ; Sun, 12 Jul 2020 10:01:33 +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 EF162206F0 for ; Sun, 12 Jul 2020 10:01:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EF162206F0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:58328 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1juYnc-0003za-2x for qemu-devel@archiver.kernel.org; Sun, 12 Jul 2020 06:01:32 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:38482) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1juYmm-0003Xm-JK for qemu-devel@nongnu.org; Sun, 12 Jul 2020 06:00:40 -0400 Received: from mx2.suse.de ([195.135.220.15]:40908) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1juYmk-0004rT-BD for qemu-devel@nongnu.org; Sun, 12 Jul 2020 06:00:40 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 7A11AAE84; Sun, 12 Jul 2020 10:00:36 +0000 (UTC) To: Juan Quintela , "Dr. David Alan Gilbert" From: Claudio Fontana Subject: migration: broken snapshot saves appear on s390 when small fields in migration stream removed Message-ID: <8bbafdec-836d-b7de-cab8-7a325b6e238d@suse.de> Date: Sun, 12 Jul 2020 12:00:34 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 Content-Language: en-US Received-SPF: pass client-ip=195.135.220.15; envelope-from=cfontana@suse.de; helo=mx2.suse.de X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/12 04:51:37 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x (no timestamps) [generic] X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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: "Jason J. Herne" , Fam Zheng , Thomas Huth , Peter Maydell , Cornelia Huck , qemu-devel , Stefan Hajnoczi , Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hello all, during unrelated work for splitting QTest from the TCG instruction counting module, I encountered what seems to be a migration stream issue, which is apparent only on s390, and only shows in block test 267. ./check -qcow2 267 when it comes to snapshot save and load using backing file. Here is a minimal reproducer patch that causes the issue on s390 only. --------------------------------------------cut------------------------------------------- ----------------------cut-------------------------- Do any of you with better understanding of migration/, block and s390 have a suggestion on what could be the issue here, and what could be the next step in the investigation? Is the fact that migration/ram.c always does fflush after writing the EOS have any relevance here? why does it do it, and should s390 code also follow the same pattern? Thanks, Claudio diff --git a/cpus.c b/cpus.c index 41d1c5099f..443b88697a 100644 --- a/cpus.c +++ b/cpus.c @@ -643,7 +643,7 @@ static void qemu_account_warp_timer(void) static bool icount_state_needed(void *opaque) { - return use_icount; + return 0; } static bool warp_timer_state_needed(void *opaque) --------------------------------------------cut------------------------------------------- config.status configure line: exec '/home/cfontana/qemu-build/../qemu/configure' '--enable-tcg' '--disable-kvm' '--disable-hax' '--target-list=s390x-softmmu' '--enable-debug' $ make check-block TEST iotest-qcow2: 267 [fail] QEMU -- "/home/cfontana/qemu-build/tests/qemu-iotests/../../s390x-softmmu/qemu-system-s390x" -nodefaults -display none -accel qtest QEMU_IMG -- "/home/cfontana/qemu-build/tests/qemu-iotests/../../qemu-img" QEMU_IO -- "/home/cfontana/qemu-build/tests/qemu-iotests/../../qemu-io" --cache writeback --aio threads -f qcow2 QEMU_NBD -- "/home/cfontana/qemu-build/tests/qemu-iotests/../../qemu-nbd" IMGFMT -- qcow2 (compat=1.1) IMGPROTO -- file PLATFORM -- Linux/s390x s390zp13 5.3.18-21-default TEST_DIR -- /home/cfontana/qemu-build/tests/qemu-iotests/scratch SOCK_DIR -- /tmp/tmp.bLJcJVtzk5 SOCKET_SCM_HELPER -- /home/cfontana/qemu-build/tests/qemu-iotests/socket_scm_helper --- /home/cfontana/qemu/tests/qemu-iotests/267.out 2020-07-12 05:10:07.948262675 -0400 +++ /home/cfontana/qemu-build/tests/qemu-iotests/267.out.bad 2020-07-12 05:27:03.358362781 -0400 @@ -137,6 +137,9 @@ ID TAG VM SIZE DATE VM CLOCK -- snap0 SIZE yyyy-mm-dd hh:mm:ss 00:00:00.000 (qemu) loadvm snap0 +Unexpected storage key flag data: 0 +error while loading state for instance 0x0 of device 's390-skeys' +Error: Error -22 while loading VM state (qemu) quit ----------- Not run: 172 186 192 259 287 Failures: 267 Failed 1 of 115 iotests make: *** [/home/cfontana/qemu/tests/Makefile.include:880: check-tests/check-block.sh] Error 1 ----------- Note: only the === -blockdev with a backing file === part of test 267 fails. -blockdev with NBD is ok, like all the rest. Interesting facts about s390 in particular: its save/load code includes the transfer of "storage keys", which include a buffer of 32768 bytes of keydata in the stream. The code (hw/s390x/s390-skeys.c), is modeled similarly to RAM transfer (like in migration/ram.c), with an EOS (end of stream) marker. Countrary to RAM transfer code though, after qemu_put_be64(f, EOS), the s390 code does not qemu_fflush(f). ---------- Observation: the migration/qemu-file.c shows an IO_BUF_SIZE of 32768. -- The following workarounds hide the problem (make the test pass): 1) always including the icount field in the (unrelated) timers field that are sent before in the migration stream (ie not applying the reproducer patch). 2) increasing the IO_BUF_SIZE also hides the problem: ----------------------cut-------------------------- diff --git a/migration/qemu-file.c b/migration/qemu-file.c index be21518c57..f81d1272eb 100644 --- a/migration/qemu-file.c +++ b/migration/qemu-file.c @@ -30,7 +30,7 @@ #include "trace.h" #include "qapi/error.h" -#define IO_BUF_SIZE 32768 +#define IO_BUF_SIZE 65536 #define MAX_IOV_SIZE MIN_CONST(IOV_MAX, 64) struct QEMUFile { ----------------------cut-------------------------- 3) adding a qemu_fflush in hw/s390x/s390-skeys.c after EOS also "fixes" the problem: ----------------------cut-------------------------- diff --git a/hw/s390x/s390-skeys.c b/hw/s390x/s390-skeys.c index 1e036cc602..47c9a015af 100644 --- a/hw/s390x/s390-skeys.c +++ b/hw/s390x/s390-skeys.c @@ -252,6 +252,8 @@ static const TypeInfo qemu_s390_skeys_info = { .class_size = sizeof(S390SKeysClass), }; +extern void qemu_fflush(QEMUFile *f); + static void s390_storage_keys_save(QEMUFile *f, void *opaque) { S390SKeysState *ss = S390_SKEYS(opaque); @@ -302,6 +304,7 @@ static void s390_storage_keys_save(QEMUFile *f, void *opaque) g_free(buf); end_stream: qemu_put_be64(f, eos); + qemu_fflush(f); } static int s390_storage_keys_load(QEMUFile *f, void *opaque, int version_id)