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 513BAC77B75 for ; Tue, 9 May 2023 18:55:52 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.532457.828688 (Exim 4.92) (envelope-from ) id 1pwSUm-0006X0-3j; Tue, 09 May 2023 18:55:32 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 532457.828688; Tue, 09 May 2023 18:55:32 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1pwSUm-0006Wt-0h; Tue, 09 May 2023 18:55:32 +0000 Received: by outflank-mailman (input) for mailman id 532457; Tue, 09 May 2023 18:55:30 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1pwSUk-0006Wj-9V for xen-devel@lists.xenproject.org; Tue, 09 May 2023 18:55:30 +0000 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id 10881ce9-ee9b-11ed-b229-6b7b168915f2; Tue, 09 May 2023 20:55:29 +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-347-hns5wC0vOUi9L7gWVTn1Ow-1; Tue, 09 May 2023 14:55:21 -0400 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id D4CC2811E7C; Tue, 9 May 2023 18:55:20 +0000 (UTC) Received: from redhat.com (unknown [10.39.194.192]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 34EDC492B00; Tue, 9 May 2023 18:55:16 +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: 10881ce9-ee9b-11ed-b229-6b7b168915f2 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1683658528; 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=4IcDDuIOaLXI9DAvceuatjdKsKxdhTRUwJDbKrSPK+8=; b=cVm5IPHZ9zfSUzvLTAnc3nRSJ46HzZwOY23l70Bodl/CeednPytYyKsF86y+BIsfjj1Axp M7WpacPKGpvQba4FBQ16jUF58yBqSg1M5AUh8JhhzMPtoYtKbELvYeU5qCLQjKbkTs+tnZ SkvflBg5vHCHMkRizq+do6hlEANa0kM= X-MC-Unique: hns5wC0vOUi9L7gWVTn1Ow-1 Date: Tue, 9 May 2023 20:55:14 +0200 From: Kevin Wolf To: Stefan Hajnoczi Cc: qemu-devel@nongnu.org, Ronnie Sahlberg , Aarushi Mehta , qemu-block@nongnu.org, Paul Durrant , Anthony Perard , Peter Lieven , Stefan Weil , Xie Yongji , Paolo Bonzini , "Michael S. Tsirkin" , Leonardo Bras , Peter Xu , Hanna Reitz , Stefano Stabellini , Richard Henderson , David Woodhouse , Coiby Xu , Eduardo Habkost , Stefano Garzarella , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , Julia Suvorova , xen-devel@lists.xenproject.org, eesposit@redhat.com, Juan Quintela , "Richard W.M. Jones" , Fam Zheng , Marcel Apfelbaum , Zhengui Li , Daniil Tatianin Subject: Re: [PATCH v5 05/21] virtio-scsi: stop using aio_disable_external() during unplug Message-ID: References: <20230504195327.695107-1-stefanha@redhat.com> <20230504195327.695107-6-stefanha@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230504195327.695107-6-stefanha@redhat.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 Am 04.05.2023 um 21:53 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. > > 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. > > Ensure virtio_scsi_hotunplug() is safe as follows: > > 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=false. > > 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! > > 2. scsi_device_unrealize() already contains a call to I think you mean scsi_qdev_unrealize(). Can be fixed while applying. > scsi_device_purge_requests() so that in-flight requests are cancelled > synchronously. This ensures that no in-flight requests remain once > qdev_simple_device_unplug_cb() returns. > > Thanks to these two conditions we don't need aio_disable_external() > anymore. > > Cc: Zhengui Li > Reviewed-by: Paolo Bonzini > Reviewed-by: Daniil Tatianin > Signed-off-by: Stefan Hajnoczi Kevin