From patchwork Thu May 4 19:53:11 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 13231740 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 7B8A2C7EE21 for ; Thu, 4 May 2023 19:59:34 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1puf1T-0005oc-QO; Thu, 04 May 2023 15:53:51 -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 1puf1R-0005ni-KB for qemu-devel@nongnu.org; Thu, 04 May 2023 15:53:49 -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 1puf1P-0006Qd-Sp for qemu-devel@nongnu.org; Thu, 04 May 2023 15:53:49 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1683230027; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=4aDv9+T5dXOUzGaYXYbFqi/phBTNlR0gw0d5Reej/CE=; b=f5T7FVYRc03MbvRIlExe9gbKsoOETSHTzWU3Fzh6P/RfSEoPmI4FVU2AK+iYBXXgLKGFG4 bwYZPHocbuIaupDQxczb+Zq0BX+YePO3TuD7FhwDYi2FB9Mh+FLoqK+W5ZQKqzcbKhqi0R d4smbNtR8GA6pLiBMgPXxsEMYIB+wuQ= 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-270-GII9Yb4pMlSDS5YQk3vVsA-1; Thu, 04 May 2023 15:53:45 -0400 X-MC-Unique: GII9Yb4pMlSDS5YQk3vVsA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 145C8886064; Thu, 4 May 2023 19:53:44 +0000 (UTC) Received: from localhost (unknown [10.39.192.57]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6F9C31121331; Thu, 4 May 2023 19:53:43 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: Ronnie Sahlberg , Aarushi Mehta , qemu-block@nongnu.org, Paul Durrant , Anthony Perard , Peter Lieven , Stefan Weil , Xie Yongji , Kevin Wolf , Paolo Bonzini , "Michael S. Tsirkin" , Leonardo Bras , Peter Xu , Hanna Reitz , Stefano Stabellini , Richard Henderson , David Woodhouse , Coiby Xu , Eduardo Habkost , Stefano Garzarella , =?utf-8?q?Philippe_Mathieu-Daud?= =?utf-8?q?=C3=A9?= , =?utf-8?q?Daniel_P=2E_Berrang=C3=A9?= , Stefan Hajnoczi , 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: [PATCH v5 05/21] virtio-scsi: stop using aio_disable_external() during unplug Date: Thu, 4 May 2023 15:53:11 -0400 Message-Id: <20230504195327.695107-6-stefanha@redhat.com> In-Reply-To: <20230504195327.695107-1-stefanha@redhat.com> References: <20230504195327.695107-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 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=-0.161, 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 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 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 --- hw/scsi/virtio-scsi.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c index ae314af3de..c1a7ea9ae2 100644 --- a/hw/scsi/virtio-scsi.c +++ b/hw/scsi/virtio-scsi.c @@ -1091,7 +1091,6 @@ static void virtio_scsi_hotunplug(HotplugHandler *hotplug_dev, DeviceState *dev, VirtIODevice *vdev = VIRTIO_DEVICE(hotplug_dev); VirtIOSCSI *s = VIRTIO_SCSI(vdev); SCSIDevice *sd = SCSI_DEVICE(dev); - AioContext *ctx = s->ctx ?: qemu_get_aio_context(); VirtIOSCSIEventInfo info = { .event = VIRTIO_SCSI_T_TRANSPORT_RESET, .reason = VIRTIO_SCSI_EVT_RESET_REMOVED, @@ -1101,9 +1100,7 @@ static void virtio_scsi_hotunplug(HotplugHandler *hotplug_dev, DeviceState *dev, }, }; - aio_disable_external(ctx); qdev_simple_device_unplug_cb(hotplug_dev, dev, errp); - aio_enable_external(ctx); if (s->ctx) { virtio_scsi_acquire(s);