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 49127C48285 for ; Thu, 25 Jan 2024 09:44:43 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rSwGu-0003Fk-MP; Thu, 25 Jan 2024 04:43:44 -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 1rSwGt-0003FO-20; Thu, 25 Jan 2024 04:43:43 -0500 Received: from proxmox-new.maurer-it.com ([94.136.29.106]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rSwGq-0005Ft-VH; Thu, 25 Jan 2024 04:43:42 -0500 Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id B71FE49259; Thu, 25 Jan 2024 10:43:38 +0100 (CET) Message-ID: <49b2548e-a9e7-47af-bc1f-6bc0c2879220@proxmox.com> Date: Thu, 25 Jan 2024 10:43:37 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] virtio: Keep notifications disabled during drain Content-Language: en-US To: Hanna Czenczek , qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, Stefan Hajnoczi , Paolo Bonzini , Kevin Wolf , "Michael S . Tsirkin" , Fam Zheng References: <20240124173834.66320-1-hreitz@redhat.com> <20240124173834.66320-3-hreitz@redhat.com> From: Fiona Ebner In-Reply-To: <20240124173834.66320-3-hreitz@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=94.136.29.106; envelope-from=f.ebner@proxmox.com; helo=proxmox-new.maurer-it.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, 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 Am 24.01.24 um 18:38 schrieb Hanna Czenczek: > During drain, we do not care about virtqueue notifications, which is why > we remove the handlers on it. When removing those handlers, whether vq > notifications are enabled or not depends on whether we were in polling > mode or not; if not, they are enabled (by default); if so, they have > been disabled by the io_poll_start callback. > > Because we do not care about those notifications after removing the > handlers, this is fine. However, we have to explicitly ensure they are > enabled when re-attaching the handlers, so we will resume receiving > notifications. We do this in virtio_queue_aio_attach_host_notifier*(). > If such a function is called while we are in a polling section, > attaching the notifiers will then invoke the io_poll_start callback, > re-disabling notifications. > > Because we will always miss virtqueue updates in the drained section, we > also need to poll the virtqueue once after attaching the notifiers. > > Buglink: https://issues.redhat.com/browse/RHEL-3934 > Signed-off-by: Hanna Czenczek Tested-by: Fiona Ebner Reviewed-by: Fiona Ebner