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 4D5C0C77B73 for ; Mon, 1 May 2023 15:10:44 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ptVAC-0006so-W9; Mon, 01 May 2023 11:10:05 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ptVAB-0006s3-1N for qemu-devel@nongnu.org; Mon, 01 May 2023 11:10:03 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ptVA8-0001aT-N6 for qemu-devel@nongnu.org; Mon, 01 May 2023 11:10:02 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1682953798; 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: in-reply-to:in-reply-to:references:references; bh=QPwbHvw4ANoG38uZDcwsHmZDGENhR6tztyBUqhJj/1o=; b=R4QyT/8U5jqNI10T1vqIMASjo9OAbp6WBNS5eh9PQWoqt/GpaQ2ujWFmZEDadrIxXQiooj pLXdp6Qg5p4P/uDPfmgiR9709ti6dPzjEUobCqSzM31hq780dxw61Bz8zqey445nkxmqZz ICyY9oMn5NjkGyT1ySz1wJgLdHZFtLM= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-650-aITlDNxzPOCmk1dkEKuuzA-1; Mon, 01 May 2023 11:09:45 -0400 X-MC-Unique: aITlDNxzPOCmk1dkEKuuzA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 32042381459C; Mon, 1 May 2023 15:09:38 +0000 (UTC) Received: from localhost (unknown [10.39.192.118]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3B641405DBBC; Mon, 1 May 2023 15:09:35 +0000 (UTC) Date: Mon, 1 May 2023 11:09:34 -0400 From: Stefan Hajnoczi To: Kevin Wolf Cc: qemu-devel@nongnu.org, Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , Juan Quintela , Julia Suvorova , xen-devel@lists.xenproject.org, eesposit@redhat.com, Richard Henderson , Fam Zheng , "Michael S. Tsirkin" , Coiby Xu , David Woodhouse , Marcel Apfelbaum , Peter Lieven , Paul Durrant , "Richard W.M. Jones" , qemu-block@nongnu.org, Stefano Garzarella , Anthony Perard , Stefan Weil , Xie Yongji , Paolo Bonzini , Aarushi Mehta , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , Eduardo Habkost , Stefano Stabellini , Hanna Reitz , Ronnie Sahlberg , Zhengui Li , Daniil Tatianin Subject: Re: [PATCH v4 04/20] virtio-scsi: stop using aio_disable_external() during unplug Message-ID: <20230501150934.GA14869@fedora> References: <20230425172716.1033562-1-stefanha@redhat.com> <20230425172716.1033562-5-stefanha@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="afWx/qHB+Kz1LRw/" Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 Received-SPF: pass client-ip=170.10.133.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -22 X-Spam_score: -2.3 X-Spam_bar: -- X-Spam_report: (-2.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.171, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, 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-bounces+qemu-devel=archiver.kernel.org@nongnu.org --afWx/qHB+Kz1LRw/ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Apr 28, 2023 at 04:22:55PM +0200, Kevin Wolf wrote: > Am 25.04.2023 um 19:27 hat Stefan Hajnoczi geschrieben: > > This patch is part of an effort to remove the aio_disable_external() > > API because it does not fit in a multi-queue block layer world where > > many AioContexts may be submitting requests to the same disk. > >=20 > > The SCSI emulation code is already in good shape to stop using > > aio_disable_external(). It was only used by commit 9c5aad84da1c > > ("virtio-scsi: fixed virtio_scsi_ctx_check failed when detaching scsi > > disk") to ensure that virtio_scsi_hotunplug() works while the guest > > driver is submitting I/O. > >=20 > > Ensure virtio_scsi_hotunplug() is safe as follows: > >=20 > > 1. qdev_simple_device_unplug_cb() -> qdev_unrealize() -> > > device_set_realized() calls qatomic_set(&dev->realized, false) so > > that future scsi_device_get() calls return NULL because they exclude > > SCSIDevices with realized=3Dfalse. > >=20 > > That means virtio-scsi will reject new I/O requests to this > > SCSIDevice with VIRTIO_SCSI_S_BAD_TARGET even while > > virtio_scsi_hotunplug() is still executing. We are protected against > > new requests! > >=20 > > 2. Add a call to scsi_device_purge_requests() from scsi_unrealize() so > > that in-flight requests are cancelled synchronously. This ensures > > that no in-flight requests remain once qdev_simple_device_unplug_cb() > > returns. > >=20 > > Thanks to these two conditions we don't need aio_disable_external() > > anymore. > >=20 > > Cc: Zhengui Li > > Reviewed-by: Paolo Bonzini > > Reviewed-by: Daniil Tatianin > > Signed-off-by: Stefan Hajnoczi >=20 > qemu-iotests 040 starts failing for me after this patch, with what looks > like a use-after-free error of some kind. >=20 > (gdb) bt > #0 0x000055b6e3e1f31c in job_type (job=3D0xe3e3e3e3e3e3e3e3) at ../job.c= :238 > #1 0x000055b6e3e1cee5 in is_block_job (job=3D0xe3e3e3e3e3e3e3e3) at ../b= lockjob.c:41 > #2 0x000055b6e3e1ce7d in block_job_next_locked (bjob=3D0x55b6e72b7570) a= t ../blockjob.c:54 > #3 0x000055b6e3df6370 in blockdev_mark_auto_del (blk=3D0x55b6e74af0a0) a= t ../blockdev.c:157 > #4 0x000055b6e393e23b in scsi_qdev_unrealize (qdev=3D0x55b6e7c04d40) at = =2E./hw/scsi/scsi-bus.c:303 > #5 0x000055b6e3db0d0e in device_set_realized (obj=3D0x55b6e7c04d40, valu= e=3Dfalse, errp=3D0x55b6e497c918 ) at ../hw/core/qdev.c:599 > #6 0x000055b6e3dba36e in property_set_bool (obj=3D0x55b6e7c04d40, v=3D0x= 55b6e7d7f290, name=3D0x55b6e41bd6d8 "realized", opaque=3D0x55b6e7246d20, er= rp=3D0x55b6e497c918 ) > at ../qom/object.c:2285 > #7 0x000055b6e3db7e65 in object_property_set (obj=3D0x55b6e7c04d40, name= =3D0x55b6e41bd6d8 "realized", v=3D0x55b6e7d7f290, errp=3D0x55b6e497c918 ) at ../qom/object.c:1420 > #8 0x000055b6e3dbd84a in object_property_set_qobject (obj=3D0x55b6e7c04d= 40, name=3D0x55b6e41bd6d8 "realized", value=3D0x55b6e74c1890, errp=3D0x55b6= e497c918 ) > at ../qom/qom-qobject.c:28 > #9 0x000055b6e3db8570 in object_property_set_bool (obj=3D0x55b6e7c04d40,= name=3D0x55b6e41bd6d8 "realized", value=3Dfalse, errp=3D0x55b6e497c918 ) at ../qom/object.c:1489 > #10 0x000055b6e3daf2b5 in qdev_unrealize (dev=3D0x55b6e7c04d40) at ../hw/= core/qdev.c:306 > #11 0x000055b6e3db509d in qdev_simple_device_unplug_cb (hotplug_dev=3D0x5= 5b6e81c3630, dev=3D0x55b6e7c04d40, errp=3D0x7ffec5519200) at ../hw/core/qde= v-hotplug.c:72 > #12 0x000055b6e3c520f9 in virtio_scsi_hotunplug (hotplug_dev=3D0x55b6e81c= 3630, dev=3D0x55b6e7c04d40, errp=3D0x7ffec5519200) at ../hw/scsi/virtio-scs= i.c:1065 > #13 0x000055b6e3db4dec in hotplug_handler_unplug (plug_handler=3D0x55b6e8= 1c3630, plugged_dev=3D0x55b6e7c04d40, errp=3D0x7ffec5519200) at ../hw/core/= hotplug.c:56 > #14 0x000055b6e3a28f84 in qdev_unplug (dev=3D0x55b6e7c04d40, errp=3D0x7ff= ec55192e0) at ../softmmu/qdev-monitor.c:935 > #15 0x000055b6e3a290fa in qmp_device_del (id=3D0x55b6e74c1760 "scsi0", er= rp=3D0x7ffec55192e0) at ../softmmu/qdev-monitor.c:955 > #16 0x000055b6e3fb0a5f in qmp_marshal_device_del (args=3D0x7f61cc005eb0, = ret=3D0x7f61d5a8ae38, errp=3D0x7f61d5a8ae40) at qapi/qapi-commands-qdev.c:1= 14 > #17 0x000055b6e3fd52e1 in do_qmp_dispatch_bh (opaque=3D0x7f61d5a8ae08) at= ../qapi/qmp-dispatch.c:128 > #18 0x000055b6e4007b9e in aio_bh_call (bh=3D0x55b6e7dea730) at ../util/as= ync.c:155 > #19 0x000055b6e4007d2e in aio_bh_poll (ctx=3D0x55b6e72447c0) at ../util/a= sync.c:184 > #20 0x000055b6e3fe3b45 in aio_dispatch (ctx=3D0x55b6e72447c0) at ../util/= aio-posix.c:421 > #21 0x000055b6e4009544 in aio_ctx_dispatch (source=3D0x55b6e72447c0, call= back=3D0x0, user_data=3D0x0) at ../util/async.c:326 > #22 0x00007f61ddc14c7f in g_main_dispatch (context=3D0x55b6e7244b20) at .= =2E/glib/gmain.c:3454 > #23 g_main_context_dispatch (context=3D0x55b6e7244b20) at ../glib/gmain.c= :4172 > #24 0x000055b6e400a7e8 in glib_pollfds_poll () at ../util/main-loop.c:290 > #25 0x000055b6e400a0c2 in os_host_main_loop_wait (timeout=3D0) at ../util= /main-loop.c:313 > #26 0x000055b6e4009fa2 in main_loop_wait (nonblocking=3D0) at ../util/mai= n-loop.c:592 > #27 0x000055b6e3a3047b in qemu_main_loop () at ../softmmu/runstate.c:731 > #28 0x000055b6e3dab27d in qemu_default_main () at ../softmmu/main.c:37 > #29 0x000055b6e3dab2b8 in main (argc=3D24, argv=3D0x7ffec55196a8) at ../s= oftmmu/main.c:48 > (gdb) p jobs > $4 =3D {lh_first =3D 0x0} I wasn't able to reproduce this with gcc 13.1.1 or clang 16.0.1: $ tests/qemu-iotests/check -qcow2 040 Any suggestions on how to reproduce the issue? Thanks, Stefan --afWx/qHB+Kz1LRw/ Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmRP1i4ACgkQnKSrs4Gr c8jU8gf7Bsg/kploFAmdPvcQ5QvmehPNQbyu4ORQkGh9WjEiJ4fROi0dXYB9yyU6 EZMpHv+mxn82F2lSoWcqD6HuuxeUJn+LVEHUzrDgcy4z9KWY8pNQmC5tijEAWnh3 0Q9G6WC9F+3GFly99ED34Ip8UJhz7IetXKMlZ+/cD8rm8YNa17cXEzZ/nHq8+aa0 SUAcymqkoOEQ9fRPQKx5TK2PW5AsZmgQE8dlmWh2c4zaWyjmZdLjE6Dap5e4l5U8 +fR9RbHAl9hMd/+SZNGzkVvZDSYMnZ8qdoEbvQ8YaxlXXaXP9gh4Mv4UBxHlOIAS Af2CAk1ye+2jhy7jM1N0qxVg5pu/oQ== =v+9M -----END PGP SIGNATURE----- --afWx/qHB+Kz1LRw/--