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 X-Spam-Level: X-Spam-Status: No, score=-19.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1EA51C433B4 for ; Mon, 19 Apr 2021 20:50:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EAB326135F for ; Mon, 19 Apr 2021 20:50:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238515AbhDSUul (ORCPT ); Mon, 19 Apr 2021 16:50:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:54616 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242091AbhDSUss (ORCPT ); Mon, 19 Apr 2021 16:48:48 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id D70AC613BC; Mon, 19 Apr 2021 20:46:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1618865161; bh=84fEXRoir9ZD96qpuD0HzoQzv/MQfRsgEFL6wgpLaVs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bovD9TbPz4fToghmomQ8kN8P2iR20mw7lUdwxCWVz3uMRga7LcjffHIVDy1+kWfH6 mTXuUOa8c/PJ2NfddB2moA1i1I/o9KC1ynwohPsM1z50EulRuU+QTPzUzF/8aMaYsj NFf4XI550QfRmnlgVVFz33ICh04xuXCoxzfB9SOcpsq43U37ogbRiqHYeOjmqQGK/u Jso9SgebJfKW6QnrzT8mu89ju0mYtPxRN7eoF2OuORy+AtcywXGsGc0AZszM2AQaKa xhPW7CS2Vggab9ln7S4GdHyFdpzV7GpF/iZSxZwdVO3dNkNbwYzldyFIUcGxRW6is5 BWYEm/sRZlgtA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Michael Brown , Paul Durrant , "David S . Miller" , Sasha Levin , xen-devel@lists.xenproject.org, netdev@vger.kernel.org Subject: [PATCH AUTOSEL 4.9 4/8] xen-netback: Check for hotplug-status existence before watching Date: Mon, 19 Apr 2021 16:45:50 -0400 Message-Id: <20210419204554.7071-4-sashal@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210419204554.7071-1-sashal@kernel.org> References: <20210419204554.7071-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Michael Brown [ Upstream commit 2afeec08ab5c86ae21952151f726bfe184f6b23d ] The logic in connect() is currently written with the assumption that xenbus_watch_pathfmt() will return an error for a node that does not exist. This assumption is incorrect: xenstore does allow a watch to be registered for a nonexistent node (and will send notifications should the node be subsequently created). As of commit 1f2565780 ("xen-netback: remove 'hotplug-status' once it has served its purpose"), this leads to a failure when a domU transitions into XenbusStateConnected more than once. On the first domU transition into Connected state, the "hotplug-status" node will be deleted by the hotplug_status_changed() callback in dom0. On the second or subsequent domU transition into Connected state, the hotplug_status_changed() callback will therefore never be invoked, and so the backend will remain stuck in InitWait. This failure prevents scenarios such as reloading the xen-netfront module within a domU, or booting a domU via iPXE. There is unfortunately no way for the domU to work around this dom0 bug. Fix by explicitly checking for existence of the "hotplug-status" node, thereby creating the behaviour that was previously assumed to exist. Signed-off-by: Michael Brown Reviewed-by: Paul Durrant Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- drivers/net/xen-netback/xenbus.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c index 78788402edd8..e6646c8a7bdb 100644 --- a/drivers/net/xen-netback/xenbus.c +++ b/drivers/net/xen-netback/xenbus.c @@ -1040,11 +1040,15 @@ static void connect(struct backend_info *be) xenvif_carrier_on(be->vif); unregister_hotplug_status_watch(be); - err = xenbus_watch_pathfmt(dev, &be->hotplug_status_watch, NULL, - hotplug_status_changed, - "%s/%s", dev->nodename, "hotplug-status"); - if (!err) + if (xenbus_exists(XBT_NIL, dev->nodename, "hotplug-status")) { + err = xenbus_watch_pathfmt(dev, &be->hotplug_status_watch, + NULL, hotplug_status_changed, + "%s/%s", dev->nodename, + "hotplug-status"); + if (err) + goto err; be->have_hotplug_status_watch = 1; + } netif_tx_wake_all_queues(be->vif->dev); -- 2.30.2