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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 7C7F7C3A5A6 for ; Thu, 19 Sep 2019 13:43:31 +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 4EE0021D56 for ; Thu, 19 Sep 2019 13:43:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4EE0021D56 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]:44282 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iAwiX-0006Tn-Pr for qemu-devel@archiver.kernel.org; Thu, 19 Sep 2019 09:43:29 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:43244) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iAw2o-0000RM-JG for qemu-devel@nongnu.org; Thu, 19 Sep 2019 09:00:24 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iAw2m-0006eC-I0 for qemu-devel@nongnu.org; Thu, 19 Sep 2019 09:00:22 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41550) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iAw2l-0006dW-Ra for qemu-devel@nongnu.org; Thu, 19 Sep 2019 09:00:20 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id EBA1630833BE; Thu, 19 Sep 2019 13:00:18 +0000 (UTC) Received: from localhost.localdomain (unknown [10.36.116.255]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 41E005C1D4; Thu, 19 Sep 2019 13:00:07 +0000 (UTC) Date: Thu, 19 Sep 2019 15:00:05 +0200 From: Kevin Wolf To: Pavel Dovgalyuk Message-ID: <20190919130005.GF10163@localhost.localdomain> References: <20190918091831.GD5207@localhost.localdomain> <001201d56e02$9d88b5f0$d89a21d0$@ru> <20190918093305.GF5207@localhost.localdomain> <001401d56e04$b93c02a0$2bb407e0$@ru> <20190918094436.GG5207@localhost.localdomain> <001501d56e06$bbd7aa30$3386fe90$@ru> <20190919085302.GA10163@localhost.localdomain> <001901d56ec9$620ae260$2620a720$@ru> <20190919112702.GC10163@localhost.localdomain> <001a01d56ee3$4354a530$c9fdef90$@ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <001a01d56ee3$4354a530$c9fdef90$@ru> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.44]); Thu, 19 Sep 2019 13:00:19 +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] [for-4.2 PATCH 3/6] replay: update docs for record/replay with block devices 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: peter.maydell@linaro.org, pavel.dovgaluk@ispras.ru, quintela@redhat.com, ciro.santilli@gmail.com, jasowang@redhat.com, crosthwaite.peter@gmail.com, qemu-devel@nongnu.org, armbru@redhat.com, alex.bennee@linaro.org, maria.klimushenkova@ispras.ru, mst@redhat.com, kraxel@redhat.com, boost.lists@gmail.com, thomas.dullien@googlemail.com, pbonzini@redhat.com, mreitz@redhat.com, artem.k.pisarenko@gmail.com, dgilbert@redhat.com, rth@twiddle.net Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 19.09.2019 um 14:10 hat Pavel Dovgalyuk geschrieben: > > From: Kevin Wolf [mailto:kwolf@redhat.com] > > Am 19.09.2019 um 11:05 hat Pavel Dovgalyuk geschrieben: > > > > From: Kevin Wolf [mailto:kwolf@redhat.com] > > > > > > > > > > > > However, global -snapshot is just a convenient shortcut for specifying > > > > > > snapshot=on for all -drive arguments. So if -snapshot is incompatible > > > > > > with replay, shouldn't manually marking all drives as snapshot=on be > > > > > > incompatible as well? > > > > > > > > > > > > Maybe you're really interested in some specific drive not having > > > > > > snapshot=on? But then it might be better to check that specific drive > > > > > > instad of forbidding just the shortcut for setting it. > > > > > > > > > > -snapshot adds the flag for top-level drive, making driver operations > > > > > dependent on temporary file structure. > > > > > > > > > > Moving this overlay beneath blkreplay driver makes drive operations > > > > > deterministic for the top-level device. > > > > > > > > So the real requirement is that blkreplay is the top-level node of any > > > > guest device, right? And only because of this, you can't use -snapshot > > > > (or snapshot=on on the blkreplay driver). > > > > > > > > If we instead check e.g. in blk_insert_bs() or blk_attach_dev() that in > > > > record/replay mode, the root node of the BlockBackend is blkreplay, > > > > wouldn't we catch many more incorrect setups? > > > > > > That sounds interesting. > > > Will it help to check that every backend is connected to blkreplay? > > > > Yes, it would return an error when you try to attach a non-blkreplay > > node to a BlockBackend (and every guest device uses a BlockBackend). > > > > Note that this restriction would currently make block jobs unavailable > > on non-blkreplay nodes as they also use BlockBackends internally (though > > this is going to change in the long run). I believe this restriction is > > harmless and the typical replay use case doesn't involve any block jobs, > > but if you do think it's a problem, blk_attach_dev() would be the place > > that affects only devices. > > > > > How then this check has to be done? > > > > Only compile-tested, but maybe something like below? > > > > Kevin > > > > diff --git a/include/block/block_int.h b/include/block/block_int.h > > index 0422acdf1c..9fa72bea51 100644 > > --- a/include/block/block_int.h > > +++ b/include/block/block_int.h > > @@ -955,6 +955,7 @@ static inline BlockDriverState *backing_bs(BlockDriverState *bs) > > extern BlockDriver bdrv_file; > > extern BlockDriver bdrv_raw; > > extern BlockDriver bdrv_qcow2; > > +extern BlockDriver bdrv_blkreplay; > > > > int coroutine_fn bdrv_co_preadv(BdrvChild *child, > > int64_t offset, unsigned int bytes, QEMUIOVector *qiov, > > diff --git a/block/blkreplay.c b/block/blkreplay.c > > index 2b7931b940..16a4f1df6a 100644 > > --- a/block/blkreplay.c > > +++ b/block/blkreplay.c > > @@ -126,7 +126,7 @@ static int coroutine_fn blkreplay_co_flush(BlockDriverState *bs) > > return ret; > > } > > > > -static BlockDriver bdrv_blkreplay = { > > +BlockDriver bdrv_blkreplay = { > > .format_name = "blkreplay", > > .instance_size = 0, > > > > diff --git a/block/block-backend.c b/block/block-backend.c > > index 1c605d5444..c57d3d9fdf 100644 > > --- a/block/block-backend.c > > +++ b/block/block-backend.c > > @@ -17,6 +17,7 @@ > > #include "block/throttle-groups.h" > > #include "hw/qdev-core.h" > > #include "sysemu/blockdev.h" > > +#include "sysemu/replay.h" > > #include "sysemu/runstate.h" > > #include "qapi/error.h" > > #include "qapi/qapi-events-block.h" > > @@ -808,6 +809,12 @@ void blk_remove_bs(BlockBackend *blk) > > int blk_insert_bs(BlockBackend *blk, BlockDriverState *bs, Error **errp) > > { > > ThrottleGroupMember *tgm = &blk->public.throttle_group_member; > > + > > + if (replay_mode != REPLAY_MODE_NONE && bs->drv != &bdrv_blkreplay) { > > + error_setg(errp, "Root node must be blkreplay"); > > + return -ENOTSUP; > > + } > > I guess this is opposite direction - bs->drv is bdrv_file. > And we should check its parent. If bs->drv is bdrv_file, you want this to fail because only bdrv_blkreplay should be able to be attached to devices. bs doesn't have any parents here in the common case, it's the root node of the BlockBackend. Kevin