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 DA4EEC4828F for ; Wed, 7 Feb 2024 21:01:26 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rXp20-0001of-GE; Wed, 07 Feb 2024 16:00:33 -0500 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 1rXp1x-0001kw-1t for qemu-devel@nongnu.org; Wed, 07 Feb 2024 16:00:29 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rXp1s-0006WH-QX for qemu-devel@nongnu.org; Wed, 07 Feb 2024 16:00:28 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1707339622; 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=O9cmddD6dLiAsM8y/+mXhCRMf1feQHqzcgr8TfDsDvo=; b=WjK6jdEbTOL4JmkVnGetEkO+TpZsgmmIin3eXlmiCU9dvpzMXXzYSl95GyPtuFEX5UyDTB qL6gMlCLNQ9qdiQC8lU7BwOtbKUoZ15gMQZcnODT6WnUNN9JKYoM6bcmd3BhS3C7D58QuT DAg+RRxTEo5bZejtFXqz3vgp2QuQdXA= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-237-h8uieEJDML6RRii9Ce2L7g-1; Wed, 07 Feb 2024 16:00:20 -0500 X-MC-Unique: h8uieEJDML6RRii9Ce2L7g-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id D0B1388F5A3; Wed, 7 Feb 2024 21:00:19 +0000 (UTC) Received: from redhat.com (unknown [10.39.192.31]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DF76D111F9; Wed, 7 Feb 2024 21:00:17 +0000 (UTC) Date: Wed, 7 Feb 2024 22:00:12 +0100 From: Kevin Wolf To: Stefan Hajnoczi Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, qemu-stable@nongnu.org, "Michael S. Tsirkin" , Hanna Reitz Subject: Re: [PATCH] virtio-blk: avoid using ioeventfd state in irqfd conditional Message-ID: References: <20240122172625.415386-1-stefanha@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240122172625.415386-1-stefanha@redhat.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.5 Received-SPF: pass client-ip=170.10.129.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.106, 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=unavailable 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 Am 22.01.2024 um 18:26 hat Stefan Hajnoczi geschrieben: > Requests that complete in an IOThread use irqfd to notify the guest > while requests that complete in the main loop thread use the traditional > qdev irq code path. The reason for this conditional is that the irq code > path requires the BQL: > > if (s->ioeventfd_started && !s->ioeventfd_disabled) { > virtio_notify_irqfd(vdev, req->vq); > } else { > virtio_notify(vdev, req->vq); > } > > There is a corner case where the conditional invokes the irq code path > instead of the irqfd code path: > > static void virtio_blk_stop_ioeventfd(VirtIODevice *vdev) > { > ... > /* > * Set ->ioeventfd_started to false before draining so that host notifiers > * are not detached/attached anymore. > */ > s->ioeventfd_started = false; > > /* Wait for virtio_blk_dma_restart_bh() and in flight I/O to complete */ > blk_drain(s->conf.conf.blk); > > During blk_drain() the conditional produces the wrong result because > ioeventfd_started is false. > > Use qemu_in_iothread() instead of checking the ioeventfd state. > > Buglink: https://issues.redhat.com/browse/RHEL-15394 > Signed-off-by: Stefan Hajnoczi Thanks, applied to the block branch. Kevin