Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030327AbcDLSIb (ORCPT ); Tue, 12 Apr 2016 14:08:31 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:49133 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030241AbcDLSI0 (ORCPT ); Tue, 12 Apr 2016 14:08:26 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Vitaly Kuznetsov , "K. Y. Srinivasan" , Greg Kroah-Hartman , Chas Williams <3chas3@gmail.com>, Luis Henriques Subject: [PATCH 3.16.y-ckt 17/17] Drivers: hv: vmbus: prevent cpu offlining on newer hypervisors Date: Tue, 12 Apr 2016 19:08:04 +0100 Message-Id: <1460484484-22395-18-git-send-email-luis.henriques@canonical.com> In-Reply-To: <1460484484-22395-1-git-send-email-luis.henriques@canonical.com> References: <1460484484-22395-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3036 Lines: 99 3.16.7-ckt27 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Vitaly Kuznetsov commit e513229b4c386e6c9f66298c13fde92f73e6e1ac upstream. 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 Signed-off-by: K. Y. Srinivasan Signed-off-by: Greg Kroah-Hartman Cc: Chas Williams <3chas3@gmail.com> [ luis: backported to 3.16: adjusted context ] Signed-off-by: Luis Henriques --- 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 4d6b26979fbd..233da0b9f4b9 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); }