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 25DCFC61DA4 for ; Thu, 16 Feb 2023 09:48:17 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pSaot-000851-NY; Thu, 16 Feb 2023 04:44:51 -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 1pSaos-00083F-3F for qemu-devel@nongnu.org; Thu, 16 Feb 2023 04:44:50 -0500 Received: from casper.infradead.org ([2001:8b0:10b:1236::1]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pSaoo-0006J4-Ln for qemu-devel@nongnu.org; Thu, 16 Feb 2023 04:44:49 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Sender:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description; bh=Brn84Bd/KTpVkrNFiD99D3sEym3orojn0xO+CrA41rM=; b=sVlbls3DctqUW0WKOXOG87z350 BT3IYr7mDcr1jzEw+/3FYvLvqXm54+U+FdRzdA9PsPWM990ln7gwpjpM4HEEooGRLJeXO+O55G1I+ wkWF2F1cMzl9Q53rthLVAv0y2f3X7FGe/qiBeRcIjCAALq1iD/IPA7akF51l0APFwn+FR7ZoAfHDz lwSaiiFDC42uMWNs7dqCaI0NLlw9ajm0u8+/wDXKxpi4jfD+MXrlRn3XnB5NA2MYOcHJ5uK/UAf28 SvFsZH0dVaVdit1CIB19o1heatRHlXHq85epwnhwfHD6ZEtESgJC7pI0EdLRxChvRaPUqKO6x333z qR5QuqfQ==; Received: from i7.infradead.org ([2001:8b0:10b:1:21e:67ff:fecb:7a92]) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1pSaoj-008IbC-Ih; Thu, 16 Feb 2023 09:44:42 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1pSaoj-0090CN-1o; Thu, 16 Feb 2023 09:44:41 +0000 From: David Woodhouse To: Peter Maydell , qemu-devel@nongnu.org Cc: Paolo Bonzini , Paul Durrant , Joao Martins , Ankur Arora , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , Thomas Huth , =?UTF-8?q?Alex=20Benn=C3=A9e?= , Juan Quintela , "Dr . David Alan Gilbert" , Claudio Fontana , Julien Grall , "Michael S. Tsirkin" , Marcel Apfelbaum , armbru@redhat.com, Stefano Stabellini , vikram.garhwal@amd.com Subject: [RFC PATCH v11bis 18/26] hw/xen: Avoid crash when backend watch fires too early Date: Thu, 16 Feb 2023 09:44:28 +0000 Message-Id: <20230216094436.2144978-19-dwmw2@infradead.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230216094436.2144978-1-dwmw2@infradead.org> References: <20230216094436.2144978-1-dwmw2@infradead.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Received-SPF: none client-ip=2001:8b0:10b:1236::1; envelope-from=BATV+33d3adc5578b079b0cf9+7116+infradead.org+dwmw2@casper.srs.infradead.org; helo=casper.infradead.org X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_NONE=0.001 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 From: Paul Durrant The xen-block code ends up calling aio_poll() through blkconf_geometry(), which means we see watch events during the indirect call to xendev_class->realize() in xen_device_realize(). Unfortunately this call is made before populating the initial frontend and backend device nodes in xenstore and hence xen_block_frontend_changed() (which is called from a watch event) fails to read the frontend's 'state' node, and hence believes the device is being torn down. This in-turn sets the backend state to XenbusStateClosed and causes the device to be deleted before it is fully set up, leading to the crash. By simply moving the call to xendev_class->realize() after the initial xenstore nodes are populated, this sorry state of affairs is avoided. Reported-by: David Woodhouse Signed-off-by: Paul Durrant Signed-off-by: David Woodhouse --- hw/xen/xen-bus.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c index e8d9adeb3e..83121c5a43 100644 --- a/hw/xen/xen-bus.c +++ b/hw/xen/xen-bus.c @@ -1031,13 +1031,6 @@ static void xen_device_realize(DeviceState *dev, Error **errp) goto unrealize; } - if (xendev_class->realize) { - xendev_class->realize(xendev, errp); - if (*errp) { - goto unrealize; - } - } - xen_device_backend_printf(xendev, "frontend", "%s", xendev->frontend_path); xen_device_backend_printf(xendev, "frontend-id", "%u", @@ -1056,6 +1049,13 @@ static void xen_device_realize(DeviceState *dev, Error **errp) xen_device_frontend_set_state(xendev, XenbusStateInitialising, true); } + if (xendev_class->realize) { + xendev_class->realize(xendev, errp); + if (*errp) { + goto unrealize; + } + } + xendev->exit.notify = xen_device_exit; qemu_add_exit_notifier(&xendev->exit); return; -- 2.39.0