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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT 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 C31C9C31E59 for ; Mon, 17 Jun 2019 12:03:03 +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 9F50321655 for ; Mon, 17 Jun 2019 12:03:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9F50321655 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]:46384 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hcqLm-0008Tg-SB for qemu-devel@archiver.kernel.org; Mon, 17 Jun 2019 08:03:02 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:57574) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hcq5Z-00077T-Ae for qemu-devel@nongnu.org; Mon, 17 Jun 2019 07:46:21 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hcq5X-0002rV-Dq for qemu-devel@nongnu.org; Mon, 17 Jun 2019 07:46:17 -0400 Received: from mx1.redhat.com ([209.132.183.28]:18046) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hcq5N-0002PS-1s; Mon, 17 Jun 2019 07:46:06 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 02C6C30BB54B; Mon, 17 Jun 2019 11:45:49 +0000 (UTC) Received: from linux.fritz.box (ovpn-117-99.ams2.redhat.com [10.36.117.99]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 495627D65D; Mon, 17 Jun 2019 11:45:46 +0000 (UTC) Date: Mon, 17 Jun 2019 13:45:44 +0200 From: Kevin Wolf To: Andrey Shinkevich Message-ID: <20190617114544.GE7397@linux.fritz.box> References: <1560276131-683243-1-git-send-email-andrey.shinkevich@virtuozzo.com> <1560276131-683243-8-git-send-email-andrey.shinkevich@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1560276131-683243-8-git-send-email-andrey.shinkevich@virtuozzo.com> User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Mon, 17 Jun 2019 11:45:54 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH v2 7/7] iotests: new file to suppress Valgrind errors 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: vsementsov@virtuozzo.com, berrange@redhat.com, qemu-block@nongnu.org, qemu-devel@nongnu.org, mreitz@redhat.com, rkagan@virtuozzo.com, den@openvz.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 11.06.2019 um 20:02 hat Andrey Shinkevich geschrieben: > The Valgrind tool reports about an uninitialised memory usage when the > initialization is actually not needed. For example, the buffer 'buf' > instantiated on a stack of the function guess_disk_lchs(). I would be careful with calling initialisation "not needed". It means that the test case may not behave entirely determinstic because the uninitialised memory can vary between runs. In this specific case, I assume that guess_disk_lchs() is called for a null block node, for which .bdrv_co_preadv by default returns without actually writing to the buffer. Instead of ignoring the valgrind error, we could instead pass read-zeroes=on to the null block driver to make the test deterministic. (Unfortunately, while adding the read-zeroes option, we didn't add it to the QAPI schema, so it's not available yet in -blockdev. I'm going to send a fix for that, but most of the problematic test cases probably don't even use -blockdev.) Kevin