From patchwork Mon Aug 31 15:01:15 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Maxim Levitsky X-Patchwork-Id: 11746431 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id DE070109B for ; Mon, 31 Aug 2020 15:04:24 +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 AF89E207EA for ; Mon, 31 Aug 2020 15:04:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="aVyeELYj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AF89E207EA 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+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Received: from localhost ([::1]:40532 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kClM7-0001wr-TM for patchwork-qemu-devel@patchwork.kernel.org; Mon, 31 Aug 2020 11:04:23 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:44150) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kClJS-00069l-3R for qemu-devel@nongnu.org; Mon, 31 Aug 2020 11:01:39 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:23409) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kClJP-0004Tt-6t for qemu-devel@nongnu.org; Mon, 31 Aug 2020 11:01:37 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1598886093; 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: content-transfer-encoding:content-transfer-encoding; bh=RJRT4zHeLM58IQVPnpfioQsjElJ0yxpdl4WV4GBXRK8=; b=aVyeELYjFDv0xPTDUezewVkP3bUHjgRcMDtr3DGUuJR7cqyuw+NO0QZ+bSQjanck9LvriC ZPIHRGQ72L+i3T3+F+wWylT5aHuvM8XJWFjCRX4sRmCnCrtw5Uc0hG3QfB/r9at6fiLyaq Hvhjxa3sgzrTMSm7CWQHtGyStmIiCOU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-490-ti5QzDIzPgym0fOGj2x3PA-1; Mon, 31 Aug 2020 11:01:31 -0400 X-MC-Unique: ti5QzDIzPgym0fOGj2x3PA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7F2D118A2242; Mon, 31 Aug 2020 15:01:30 +0000 (UTC) Received: from localhost.localdomain (unknown [10.35.206.190]) by smtp.corp.redhat.com (Postfix) with ESMTP id 729BE19C4F; Mon, 31 Aug 2020 15:01:25 +0000 (UTC) From: Maxim Levitsky To: qemu-devel@nongnu.org Subject: [PATCH v4 0/9] Fix scsi devices plug/unplug races w.r.t virtio-scsi iothread Date: Mon, 31 Aug 2020 18:01:15 +0300 Message-Id: <20200831150124.206267-1-mlevitsk@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mlevitsk@redhat.com X-Mimecast-Spam-Score: 0.003 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=63.128.21.124; envelope-from=mlevitsk@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/31 03:02:42 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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: Fam Zheng , =?utf-8?q?Daniel_P=2E_Berrang=C3=A9?= , Eduardo Habkost , "Michael S. Tsirkin" , Maxim Levitsky , Paolo Bonzini Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" Hi! This is a patch series that is a result of my discussion with Paulo on how to correctly fix the root cause of the BZ #1812399. The root cause of this bug is the fact that IO thread is running mostly unlocked versus main thread on which device hotplug is done. qdev_device_add first creates the device object, then places it on the bus, and only then realizes it. However some drivers and currently only virtio-scsi enumerate its child bus devices on each request that is received from the guest and that can happen on the IO thread. Thus we have a window when new device is on the bus but not realized and can be accessed by the virtio-scsi driver in that state. Fix that by doing two things: 1. Add partial RCU protection to the list of a bus's child devices. This allows the scsi IO thread to safely enumerate the child devices while it races with the hotplug placing the device on the bus. 2. Let scsi_device_find not return devices that are on the bus but not realized Note that in the particular bug report the issue wasn't a race but rather due to combination of things, the .realize code in the middle managed to trigger IO on the virtqueue which caused the virtio-scsi driver to access the half realized device. However since this can happen as well with real IO thread, this patch series was done, which fixes this as well. Changes from V3: * Rebased to latest qemu * Added a new patch to fix related race in scsi_target_emulate_report_luns * Moved the non-realized device check to scsi core, since there is no way a device driver will want to see non realized devices on a scsi bus. (scsi-bus still needs this and can using an internal function) * Splitted patch that added drain_rcu and used it, to patch that only adds it, and one that uses it (no other changes so I kept Reviewed-by) *Some tweaks to commits This series was tested by adding a virtio-scsi drive with iothread, then running fio stress job in the guest in a loop, and then adding/removing the scsi drive on the host in the loop. This test was failing usually on 1st iteration withouth this patch series, and now it seems to work smoothly. Best regards, Maxim Levitsky Maxim Levitsky (9): scsi/scsi_bus: switch search direction in scsi_device_find rcu: Implement drain_call_rcu device_core: use drain_call_rcu in in hmp_device_del/qmp_device_add device-core: use RCU for list of childs of a bus device-core: use atomic_set on .realized property scsi/scsi-bus: scsi_device_find: don't return unrealized devices scsi/scsi_bus: Add scsi_device_get virtio-scsi: use scsi_device_get scsi/scsi_bus: fix races in REPORT LUNS hw/core/bus.c | 28 +++++--- hw/core/qdev.c | 56 +++++++++++---- hw/scsi/scsi-bus.c | 151 ++++++++++++++++++++++++++--------------- hw/scsi/virtio-scsi.c | 27 +++++--- include/hw/qdev-core.h | 11 +++ include/hw/scsi/scsi.h | 1 + include/qemu/rcu.h | 1 + qdev-monitor.c | 22 ++++++ util/rcu.c | 55 +++++++++++++++ 9 files changed, 265 insertions(+), 87 deletions(-)