From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754724AbbDTK27 (ORCPT ); Mon, 20 Apr 2015 06:28:59 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38419 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753949AbbDTK25 (ORCPT ); Mon, 20 Apr 2015 06:28:57 -0400 From: Vitaly Kuznetsov To: "K. Y. Srinivasan" Cc: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, devel@linuxdriverproject.org, olaf@aepfle.de, apw@canonical.com, jasowang@redhat.com Subject: Re: [PATCH 5/5] Drivers: hv: vmbus: Implement the protocol for tearing down vmbus state References: <1429515878-13710-1-git-send-email-kys@microsoft.com> <1429515905-13749-1-git-send-email-kys@microsoft.com> <1429515905-13749-5-git-send-email-kys@microsoft.com> <87twwbcf4h.fsf@vitty.brq.redhat.com> Date: Mon, 20 Apr 2015 12:28:41 +0200 In-Reply-To: <87twwbcf4h.fsf@vitty.brq.redhat.com> (Vitaly Kuznetsov's message of "Mon, 20 Apr 2015 11:39:58 +0200") Message-ID: <878udnccva.fsf@vitty.brq.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Vitaly Kuznetsov writes: > "K. Y. Srinivasan" writes: > >> Implement the protocol for tearing down the monitor state established with >> the host. >> >> Signed-off-by: K. Y. Srinivasan > > Unfortunatelly this patch leads to the following crash: > > pre-udev:/# modprobe hv_vmbus > modprobe hv_vmbus > [ 14.832334] hv_vmbus: Hyper-V Host Build:9600-6.3-17-0.17039; Vmbus version:3.0 > [ 14.834179] hv_vmbus: CPU offlining is not supported by hypervisor > pre-udev:/# modprobe -r hv_vmbus > modprobe -r hv_vmbus > [ 20.640893] BUG: unable to handle kernel NULL pointer dereference at (null) > [ 20.641104] IP: [< (null)>] (null) > > I'll try to investigate. > The problem is that we call vmbus_disconnect() too late in vmbus_exit(). We need to call it: 1) Before hv_cleanup() call as we free hypercall page there (that's what you see in my crash) 2) Before hv_remove_vmbus_irq() as we're waiting for the hypervisor to reply. This simple patch fixes the issue: diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 7870a90..2b56260 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -1106,6 +1106,7 @@ static void __exit vmbus_exit(void) vmbus_connection.conn_state = DISCONNECTED; hv_synic_clockevents_cleanup(); + vmbus_disconnect(); hv_remove_vmbus_irq(); vmbus_free_channels(); if (ms_hyperv.features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) { @@ -1118,7 +1119,6 @@ static void __exit vmbus_exit(void) smp_call_function_single(cpu, hv_synic_cleanup, NULL, 1); acpi_bus_unregister_driver(&vmbus_acpi_driver); hv_cpu_hotplug_quirk(false); - vmbus_disconnect(); } I suggest we incorporate it into your PATCH 5/5. -- Vitaly