From nobody Mon Feb 9 19:07:35 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) client-ip=192.237.175.120; envelope-from=xen-devel-bounces@lists.xenproject.org; helo=lists.xenproject.org; Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; dmarc=pass(p=quarantine dis=none) header.from=suse.com ARC-Seal: i=1; a=rsa-sha256; t=1621354464; cv=none; d=zohomail.com; s=zohoarc; b=ZES9mkYQ7Ka6/4bRyWgHzy8+I4iqPbvPkilYzl4ieMuUugAxegFlok2SjHKynxYGw4fnbO+99lkrltAzxt+YzAkqioNwChPCiV4xG6dFvP5MYfqsTYHbv45FEfEb7zlG1ophD/lU3iq93O/pqAGmehu9jq8GfzFNJ91013ruGAI= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1621354464; h=Content-Type:Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To; bh=3Qh/UZ1VOm2y48tyKXzASGbqQVo3psCNIRYWaNH1KbM=; b=U0KNHPQO4TZh74cnHJS6yg6K82+JNHSabsdclHGqcAVxB4Em35qOkY+0j/I7Dms8ACIFhv6cxKvO6G7niCh5kJ/Qpt57oRANWTFg3rzQ8ECYBpFYRtHn/9IK1bAf9JfAyYyI4BDn+ysEWA2KXtkGyJDswQK5ezhum2JH/zKBiEQ= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; dmarc=pass header.from= (p=quarantine dis=none) header.from= Return-Path: Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) by mx.zohomail.com with SMTPS id 1621354464627939.2017873234383; Tue, 18 May 2021 09:14:24 -0700 (PDT) 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 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-Outflank-Mailman: Message body and most headers restored to incoming version 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-Language: en-US Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @suse.com) Content-Type: text/plain; charset="utf-8" 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 Reviewed-by: Boris Ostrovsky --- 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; } =20 -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 =3D 0; int num_devs; @@ -373,9 +374,7 @@ static int xen_pcibk_reconfigure(struct dev_dbg(&pdev->xdev->dev, "Reconfiguring device ...\n"); =20 mutex_lock(&pdev->dev_lock); - /* Make sure we only reconfigure once */ - if (xenbus_read_driver_state(pdev->xdev->nodename) !=3D - XenbusStateReconfiguring) + if (xenbus_read_driver_state(pdev->xdev->nodename) !=3D state) goto out; =20 err =3D xenbus_scanf(XBT_NIL, pdev->xdev->nodename, "num_devs", "%d", @@ -500,6 +499,10 @@ static int xen_pcibk_reconfigure(struct } } =20 + if (state !=3D XenbusStateReconfiguring) + /* Make sure we only reconfigure once. */ + goto out; + err =3D 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; =20 case XenbusStateReconfiguring: - xen_pcibk_reconfigure(pdev); + xen_pcibk_reconfigure(pdev, XenbusStateReconfiguring); break; =20 case XenbusStateConnected: @@ -664,6 +667,15 @@ static void xen_pcibk_be_watch(struct xe xen_pcibk_setup_backend(pdev); break; =20 + 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; }