From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751623AbbALQuX (ORCPT ); Mon, 12 Jan 2015 11:50:23 -0500 Received: from mx1.redhat.com ([209.132.183.28]:55641 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750964AbbALQuW (ORCPT ); Mon, 12 Jan 2015 11:50:22 -0500 From: Vitaly Kuznetsov To: "K. Y. Srinivasan" , devel@linuxdriverproject.org Cc: Haiyang Zhang , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Dexuan Cui Subject: [PATCH v3] Drivers: hv: vmbus: prevent cpu offlining on newer hypervisors Date: Mon, 12 Jan 2015 17:50:11 +0100 Message-Id: <1421081411-5759-1-git-send-email-vkuznets@redhat.com> In-Reply-To: <1417431161-12845-1-git-send-email-vkuznets@redhat.com> References: <1417431161-12845-1-git-send-email-vkuznets@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When an SMP Hyper-V guest is running on top of 2012R2 Server and secondary cpus are sent offline (with echo 0 > /sys/devices/system/cpu/cpu$cpu/online) the system freeze is observed. This happens due to the fact that on newer hypervisors (Win8, WS2012R2, ...) vmbus channel handlers are distributed across all cpus (see init_vp_index() function in drivers/hv/channel_mgmt.c) and on cpu offlining nobody reassigns them to CPU0. Prevent cpu offlining when vmbus is loaded until the issue is fixed host-side. This patch also disables hibernation but it is OK as it is also broken (MCE error is hit on resume). Suspend still works. Tested with WS2008R2 and WS2012R2. Signed-off-by: Vitaly Kuznetsov --- Changes since v2: - repair the build when vmbus is builded as a module [Greg KH] by saving current cpu_disable pointer to previous_cpu_disable and restoring it on unload; - return -ENOSYS (same as native_cpu_disable when !CONFIG_HOTPLUG_CPU) instead of -1 in hyperv_cpu_disable(). Changes since v1: - introduce hv_cpu_hotplug_quirk() function to not spread #ifdefs [Greg KH]; - add pr_notice() message "hv_vmbus: CPU offlining is not supported by hypervisor". --- drivers/hv/vmbus_drv.c | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 4d6b269..233da0b 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -32,6 +32,7 @@ #include #include #include +#include #include #include #include @@ -671,6 +672,39 @@ static void vmbus_isr(void) tasklet_schedule(&msg_dpc); } +#ifdef CONFIG_HOTPLUG_CPU +static int hyperv_cpu_disable(void) +{ + return -ENOSYS; +} + +static void hv_cpu_hotplug_quirk(bool vmbus_loaded) +{ + static void *previous_cpu_disable; + + /* + * Offlining a CPU when running on newer hypervisors (WS2012R2, Win8, + * ...) is not supported at this moment as channel interrupts are + * distributed across all of them. + */ + + if ((vmbus_proto_version == VERSION_WS2008) || + (vmbus_proto_version == VERSION_WIN7)) + return; + + if (vmbus_loaded) { + previous_cpu_disable = smp_ops.cpu_disable; + smp_ops.cpu_disable = hyperv_cpu_disable; + pr_notice("CPU offlining is not supported by hypervisor\n"); + } else if (previous_cpu_disable) + smp_ops.cpu_disable = previous_cpu_disable; +} +#else +static void hv_cpu_hotplug_quirk(bool vmbus_loaded) +{ +} +#endif + /* * vmbus_bus_init -Main vmbus driver initialization routine. * @@ -711,6 +745,7 @@ static int vmbus_bus_init(int irq) if (ret) goto err_alloc; + hv_cpu_hotplug_quirk(true); vmbus_request_offers(); return 0; @@ -964,6 +999,7 @@ static void __exit vmbus_exit(void) bus_unregister(&hv_bus); hv_cleanup(); acpi_bus_unregister_driver(&vmbus_acpi_driver); + hv_cpu_hotplug_quirk(false); } -- 1.9.3