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.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 A9502C77B73 for ; Tue, 2 May 2023 20:03:21 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.528802.822405 (Exim 4.92) (envelope-from ) id 1ptwD9-0002UO-T7; Tue, 02 May 2023 20:02:55 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 528802.822405; Tue, 02 May 2023 20:02:55 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1ptwD9-0002UH-Pt; Tue, 02 May 2023 20:02:55 +0000 Received: by outflank-mailman (input) for mailman id 528802; Tue, 02 May 2023 20:02:54 +0000 Received: from se1-gles-flk1-in.inumbo.com ([94.247.172.50] helo=se1-gles-flk1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1ptwD8-0002UB-MN for xen-devel@lists.xenproject.org; Tue, 02 May 2023 20:02:54 +0000 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by se1-gles-flk1.inumbo.com (Halon) with ESMTPS id 506a762f-e924-11ed-8611-37d641c3527e; Tue, 02 May 2023 22:02:50 +0200 (CEST) Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-551-8i9sxkcoOrucqmHkxzDdSA-1; Tue, 02 May 2023 16:02:47 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id C708A101A531; Tue, 2 May 2023 20:02:46 +0000 (UTC) Received: from localhost (unknown [10.39.192.230]) by smtp.corp.redhat.com (Postfix) with ESMTP id B65FF63F5B; Tue, 2 May 2023 20:02:45 +0000 (UTC) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 506a762f-e924-11ed-8611-37d641c3527e DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1683057769; 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=7lfhqttiODmbNxuxzmQIGPLL6DVlwheJNNJYYd5PHZI=; b=AGFtq8/EGGpm3JUeI6/CRMExUZ6AnZ5zcqDaOdxHzwxRxLC1k41BXmbB7V/2ZQznGsWuQ2 6UXIAgqnPhyJc54mAl82el0Q/+FQQv8R22QPGyAhZPHmsL7on8f/869spz1FFVqXnORij1 f1cRVtmlXDbCO5FcsKSFWKc88FvPOTE= X-MC-Unique: 8i9sxkcoOrucqmHkxzDdSA-1 Date: Tue, 2 May 2023 16:02:43 -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: <20230502200243.GD535070@fedora> References: <20230425172716.1033562-1-stefanha@redhat.com> <20230425172716.1033562-5-stefanha@redhat.com> <20230501150934.GA14869@fedora> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="KLJLJshWTSqDDVpb" Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 --KLJLJshWTSqDDVpb Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, May 02, 2023 at 03:19:52PM +0200, Kevin Wolf wrote: > Am 01.05.2023 um 17:09 hat Stefan Hajnoczi geschrieben: > > 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 sc= si > > > > 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 exc= lude > > > > 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 aga= inst > > > > 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 lo= oks > > > like a use-after-free error of some kind. > > >=20 > > > (gdb) bt > > > #0 0x000055b6e3e1f31c in job_type (job=3D0xe3e3e3e3e3e3e3e3) at ../j= ob.c:238 > > > #1 0x000055b6e3e1cee5 in is_block_job (job=3D0xe3e3e3e3e3e3e3e3) at = =2E./blockjob.c:41 > > > #2 0x000055b6e3e1ce7d in block_job_next_locked (bjob=3D0x55b6e72b757= 0) at ../blockjob.c:54 > > > #3 0x000055b6e3df6370 in blockdev_mark_auto_del (blk=3D0x55b6e74af0a= 0) at ../blockdev.c:157 > > > #4 0x000055b6e393e23b in scsi_qdev_unrealize (qdev=3D0x55b6e7c04d40)= at ../hw/scsi/scsi-bus.c:303 > > > #5 0x000055b6e3db0d0e in device_set_realized (obj=3D0x55b6e7c04d40, = value=3Dfalse, errp=3D0x55b6e497c918 ) at ../hw/core/qdev.c:599 > > > #6 0x000055b6e3dba36e in property_set_bool (obj=3D0x55b6e7c04d40, v= =3D0x55b6e7d7f290, name=3D0x55b6e41bd6d8 "realized", opaque=3D0x55b6e7246d2= 0, errp=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=3D0x55b6e7= c04d40, name=3D0x55b6e41bd6d8 "realized", value=3D0x55b6e74c1890, errp=3D0x= 55b6e497c918 ) > > > at ../qom/qom-qobject.c:28 > > > #9 0x000055b6e3db8570 in object_property_set_bool (obj=3D0x55b6e7c04= d40, 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= =3D0x55b6e81c3630, dev=3D0x55b6e7c04d40, errp=3D0x7ffec5519200) at ../hw/co= re/qdev-hotplug.c:72 > > > #12 0x000055b6e3c520f9 in virtio_scsi_hotunplug (hotplug_dev=3D0x55b6= e81c3630, dev=3D0x55b6e7c04d40, errp=3D0x7ffec5519200) at ../hw/scsi/virtio= -scsi.c:1065 > > > #13 0x000055b6e3db4dec in hotplug_handler_unplug (plug_handler=3D0x55= b6e81c3630, plugged_dev=3D0x55b6e7c04d40, errp=3D0x7ffec5519200) at ../hw/c= ore/hotplug.c:56 > > > #14 0x000055b6e3a28f84 in qdev_unplug (dev=3D0x55b6e7c04d40, errp=3D0= x7ffec55192e0) at ../softmmu/qdev-monitor.c:935 > > > #15 0x000055b6e3a290fa in qmp_device_del (id=3D0x55b6e74c1760 "scsi0"= , errp=3D0x7ffec55192e0) at ../softmmu/qdev-monitor.c:955 > > > #16 0x000055b6e3fb0a5f in qmp_marshal_device_del (args=3D0x7f61cc005e= b0, ret=3D0x7f61d5a8ae38, errp=3D0x7f61d5a8ae40) at qapi/qapi-commands-qdev= =2Ec:114 > > > #17 0x000055b6e3fd52e1 in do_qmp_dispatch_bh (opaque=3D0x7f61d5a8ae08= ) at ../qapi/qmp-dispatch.c:128 > > > #18 0x000055b6e4007b9e in aio_bh_call (bh=3D0x55b6e7dea730) at ../uti= l/async.c:155 > > > #19 0x000055b6e4007d2e in aio_bh_poll (ctx=3D0x55b6e72447c0) at ../ut= il/async.c:184 > > > #20 0x000055b6e3fe3b45 in aio_dispatch (ctx=3D0x55b6e72447c0) at ../u= til/aio-posix.c:421 > > > #21 0x000055b6e4009544 in aio_ctx_dispatch (source=3D0x55b6e72447c0, = callback=3D0x0, user_data=3D0x0) at ../util/async.c:326 > > > #22 0x00007f61ddc14c7f in g_main_dispatch (context=3D0x55b6e7244b20) = at ../glib/gmain.c:3454 > > > #23 g_main_context_dispatch (context=3D0x55b6e7244b20) at ../glib/gma= in.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= /main-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 = =2E./softmmu/main.c:48 > > > (gdb) p jobs > > > $4 =3D {lh_first =3D 0x0} > >=20 > > I wasn't able to reproduce this with gcc 13.1.1 or clang 16.0.1: > >=20 > > $ tests/qemu-iotests/check -qcow2 040 > >=20 > > Any suggestions on how to reproduce the issue? >=20 > It happens consistently for me with the same command line, both with gcc > and clang. >=20 > gcc (GCC) 12.2.1 20221121 (Red Hat 12.2.1-4) > clang version 15.0.7 (Fedora 15.0.7-2.fc37) >=20 > Maybe there is a semantic merge conflict? I have applied the series on > top of master (05d50ba2d4) and my block branch (88f81f7bc8). I can't find 88f81f7bc8 but rebased on repo.or.cz/qemu/kevin.git block (4514dac7f2e9) and the test passes here. I rebased on qemu.git/master (05d50ba2d4) and it also passes. Please let me know if the following tree (a0ff680a72f6) works on your machine: https://gitlab.com/stefanha/qemu/-/tree/remove-aio_disable_external Thanks, Stefan --KLJLJshWTSqDDVpb Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmRRbGMACgkQnKSrs4Gr c8iL5Af+MRYfwim9BEWCQ+OFF9rPydT4E+bBnTgMftUJz8XcaxXz5sDzpq3sXhvM UXDSMHg1/RY38aMEGGT1kPtlxI3zUO3pwNckFeU3rpqa22dI1yxMwI92Rn29LLIk 8txmNTd4eG89Vgvvl3zrqV/budvInTRmy7ZtMgMnNJ+SGAMxWWtakCZlBQzw7WBh 946sfiub2lvQKnvBgQJJLCOfVs3drSqV9+4IdzkpGwjN5fruVe3WhKC98Ha88ACF L4cpa9MvlMyJvrxmPdB2uL8Eyn1mV3uLVi8Z0nRwiy4/mtahrGMZ3jkEJNi3Zn12 qpT/iMyl9DjsAj5nh2ElduicM7QFgw== =9x4Q -----END PGP SIGNATURE----- --KLJLJshWTSqDDVpb--