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=-17.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 98AE5C433B4 for ; Tue, 18 May 2021 16:14:18 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 5B886611CE for ; Tue, 18 May 2021 16:14:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5B886611CE Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.129431.242948 (Exim 4.92) (envelope-from ) id 1lj2MF-0001Es-6h; Tue, 18 May 2021 16:14:11 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 129431.242948; Tue, 18 May 2021 16:14:11 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lj2MF-0001El-3K; Tue, 18 May 2021 16:14:11 +0000 Received: by outflank-mailman (input) for mailman id 129431; Tue, 18 May 2021 16:14:10 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lj2ME-0001CC-3m for xen-devel@lists.xenproject.org; Tue, 18 May 2021 16:14:10 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 8495d333-d79c-45f0-994d-3ecf211878bc; Tue, 18 May 2021 16:14:09 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 68702ABED; Tue, 18 May 2021 16:14:08 +0000 (UTC) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 8495d333-d79c-45f0-994d-3ecf211878bc X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1621354448; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3Qh/UZ1VOm2y48tyKXzASGbqQVo3psCNIRYWaNH1KbM=; b=BBDARNgKmSrexkj1M/FtvHzFy3OiIqf5YV/0KY1P9OL4vf2FFYZfOnZKts8XQVPRj3Otce xY0bwqdrovRTCwslvfcOtSo+nQYLWkXTK/i+hl1XKuOc8zaB4wqzw30jKi6MXYm9x8WpVf rflxrlwLXkO7fLhkuJtOnbdmAgYZBv8= Subject: [PATCH v2 2/2] xen-pciback: reconfigure also from backend watch handler From: Jan Beulich To: "xen-devel@lists.xenproject.org" Cc: Juergen Gross , Boris Ostrovsky , Konrad Wilk References: <38774140-871d-59a4-cf49-9cb1cc78c381@suse.com> Message-ID: <2337cbd6-94b9-4187-9862-c03ea12e0c61@suse.com> Date: Tue, 18 May 2021 18:14:07 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <38774140-871d-59a4-cf49-9cb1cc78c381@suse.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit When multiple PCI devices get assigned to a guest right at boot, libxl incrementally populates the backend tree. The writes for the first of the devices trigger the backend watch. In turn xen_pcibk_setup_backend() will set the XenBus state to Initialised, at which point no further reconfigures would happen unless a device got hotplugged. Arrange for reconfigure to also get triggered from the backend watch handler. Signed-off-by: Jan Beulich Cc: stable@vger.kernel.org --- v2: Also move comment. Add a comment. --- I will admit that this isn't entirely race-free (with the guest actually attaching in parallel), but from the looks of it such a race ought to be benign (not the least thanks to the mutex). Ideally the tool stack wouldn't write num_devs until all devices had their information populated. I tried doing so in libxl, but xen_pcibk_setup_backend() calling xenbus_dev_fatal() when not being able to read that node prohibits such an approach (or else libxl and driver changes would need to go into use in lock-step). I wonder why what is being watched isn't just the num_devs node. Right now the watch triggers quite frequently without anything relevant actually having changed (I suppose in at least some cases in response to writes by the backend itself). --- a/drivers/xen/xen-pciback/xenbus.c +++ b/drivers/xen/xen-pciback/xenbus.c @@ -359,7 +359,8 @@ out: return err; } -static int xen_pcibk_reconfigure(struct xen_pcibk_device *pdev) +static int xen_pcibk_reconfigure(struct xen_pcibk_device *pdev, + enum xenbus_state state) { int err = 0; int num_devs; @@ -373,9 +374,7 @@ static int xen_pcibk_reconfigure(struct dev_dbg(&pdev->xdev->dev, "Reconfiguring device ...\n"); mutex_lock(&pdev->dev_lock); - /* Make sure we only reconfigure once */ - if (xenbus_read_driver_state(pdev->xdev->nodename) != - XenbusStateReconfiguring) + if (xenbus_read_driver_state(pdev->xdev->nodename) != state) goto out; err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename, "num_devs", "%d", @@ -500,6 +499,10 @@ static int xen_pcibk_reconfigure(struct } } + if (state != XenbusStateReconfiguring) + /* Make sure we only reconfigure once. */ + goto out; + err = xenbus_switch_state(pdev->xdev, XenbusStateReconfigured); if (err) { xenbus_dev_fatal(pdev->xdev, err, @@ -525,7 +528,7 @@ static void xen_pcibk_frontend_changed(s break; case XenbusStateReconfiguring: - xen_pcibk_reconfigure(pdev); + xen_pcibk_reconfigure(pdev, XenbusStateReconfiguring); break; case XenbusStateConnected: @@ -664,6 +667,15 @@ static void xen_pcibk_be_watch(struct xe xen_pcibk_setup_backend(pdev); break; + case XenbusStateInitialised: + /* + * We typically move to Initialised when the first device was + * added. Hence subsequent devices getting added may need + * reconfiguring. + */ + xen_pcibk_reconfigure(pdev, XenbusStateInitialised); + break; + default: break; }