From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755270AbbAZKjK (ORCPT ); Mon, 26 Jan 2015 05:39:10 -0500 Received: from mx1.redhat.com ([209.132.183.28]:48826 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754679AbbAZKjG (ORCPT ); Mon, 26 Jan 2015 05:39:06 -0500 From: Vitaly Kuznetsov To: Greg Kroah-Hartman Cc: "K. Y. Srinivasan" , devel@linuxdriverproject.org, Haiyang Zhang , linux-kernel@vger.kernel.org, Dexuan Cui Subject: Re: [PATCH v3] Drivers: hv: vmbus: prevent cpu offlining on newer hypervisors References: <1417431161-12845-1-git-send-email-vkuznets@redhat.com> <1421081411-5759-1-git-send-email-vkuznets@redhat.com> <20150125133659.GA21552@kroah.com> Date: Mon, 26 Jan 2015 11:38:54 +0100 In-Reply-To: <20150125133659.GA21552@kroah.com> (Greg Kroah-Hartman's message of "Sun, 25 Jan 2015 21:36:59 +0800") Message-ID: <87k309g729.fsf@vitty.brq.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="=-=-=" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=-=-= Content-Type: text/plain Greg Kroah-Hartman writes: > On Mon, Jan 12, 2015 at 05:50:11PM +0100, Vitaly Kuznetsov wrote: >> 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 >> --- >> 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(+) > > Doesn't apply to my char-misc-test branch at all :( Another mid-air collision with K.Y's "Drivers: hv: vmbus: Implement a clockevent device", please use the attached version. No functional changes are required, I just fixed the merge conflict (includes). Othere than that (and sorry for meddling), would it it be better if you switch to 'pull requests' workflow with K.Y? There is a lot of ongoing work in hyperv nowdays and such collisions seem otherwise inevitable ... -- Vitaly --=-=-= Content-Type: text/x-patch Content-Disposition: inline; filename=0001-Drivers-hv-vmbus-prevent-cpu-offlining-on-newer-hype.patch >>From 95f9b0ff3f73c3bbe8aa9c525414097c2c26a3ef Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov Date: Mon, 12 Jan 2015 17:50:11 +0100 Subject: [PATCH] Drivers: hv: vmbus: prevent cpu offlining on newer hypervisors 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 --- 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 35e3f42..90c3400 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -33,6 +33,7 @@ #include #include #include +#include #include #include #include @@ -704,6 +705,39 @@ static void vmbus_isr(void) } } +#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. * @@ -744,6 +778,7 @@ static int vmbus_bus_init(int irq) if (ret) goto err_alloc; + hv_cpu_hotplug_quirk(true); vmbus_request_offers(); return 0; @@ -997,6 +1032,7 @@ 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 --=-=-=--