Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754249AbcKYM5Z (ORCPT ); Fri, 25 Nov 2016 07:57:25 -0500 Received: from mx1.redhat.com ([209.132.183.28]:60812 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753171AbcKYM5G (ORCPT ); Fri, 25 Nov 2016 07:57:06 -0500 From: Vitaly Kuznetsov To: devel@linuxdriverproject.org Cc: linux-kernel@vger.kernel.org, "K. Y. Srinivasan" , Haiyang Zhang , Dexuan Cui , Stephen Hemminger Subject: [PATCH 7/7] hv: make CPU offlining prevention fine-grained Date: Fri, 25 Nov 2016 13:48:43 +0100 Message-Id: <1480078123-17582-8-git-send-email-vkuznets@redhat.com> In-Reply-To: <1480078123-17582-1-git-send-email-vkuznets@redhat.com> References: <1480078123-17582-1-git-send-email-vkuznets@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Fri, 25 Nov 2016 12:48:59 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3409 Lines: 105 Since commit e513229b4c38 ("Drivers: hv: vmbus: prevent cpu offlining on newer hypervisors") cpu offlining was disabled. It is still true that we can't offline CPUs which have VMBus channels bound to them but we may have 'free' CPUs (e.v. we booted with maxcpus= parameter and onlined CPUs after VMBus was initialized), these CPUs may be disabled without issues. In future, we may even allow closing CPUs which have only sub-channels assinged to them by closing these sub-channels. All devices will continue to work. Signed-off-by: Vitaly Kuznetsov --- drivers/hv/hv.c | 31 +++++++++++++++++++++++++++++++ drivers/hv/vmbus_drv.c | 9 ++++----- 2 files changed, 35 insertions(+), 5 deletions(-) diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c index b3f6a1b..4ece040 100644 --- a/drivers/hv/hv.c +++ b/drivers/hv/hv.c @@ -586,10 +586,41 @@ int hv_synic_cleanup(unsigned int cpu) union hv_synic_simp simp; union hv_synic_siefp siefp; union hv_synic_scontrol sctrl; + struct vmbus_channel *channel, *sc; + bool channel_found = false; + unsigned long flags; if (!hv_context.synic_initialized) return -EFAULT; + /* + * Search for channels which are bound to the CPU we're about to + * cleanup. In case we find one and vmbus is still connected we need to + * fail, this will effectively prevent CPU offlining. There is no way + * we can re-bind channels to different CPUs for now. + */ + mutex_lock(&vmbus_connection.channel_mutex); + list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) { + if (channel->target_cpu == cpu) { + channel_found = true; + break; + } + spin_lock_irqsave(&channel->lock, flags); + list_for_each_entry(sc, &channel->sc_list, sc_list) { + if (sc->target_cpu == cpu) { + channel_found = true; + break; + } + } + spin_unlock_irqrestore(&channel->lock, flags); + if (channel_found) + break; + } + mutex_unlock(&vmbus_connection.channel_mutex); + + if (channel_found && vmbus_connection.conn_state == CONNECTED) + return -EBUSY; + /* Turn off clockevent device */ if (ms_hyperv.features & HV_X64_MSR_SYNTIMER_AVAILABLE) { clockevents_unbind_device(hv_context.clk_evt[cpu], cpu); diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index a115c90..61d879f 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -855,9 +855,6 @@ static int vmbus_bus_init(void) if (ret) goto err_connect; - if (vmbus_proto_version > VERSION_WIN7) - cpu_hotplug_disable(); - /* * Only register if the crash MSRs are available */ @@ -1328,6 +1325,9 @@ static void hv_kexec_handler(void) { hv_synic_clockevents_cleanup(); vmbus_initiate_unload(false); + vmbus_connection.conn_state = DISCONNECTED; + /* Make sure conn_state is set as hv_synic_cleanup checks for it */ + mb(); cpuhp_remove_state(hyperv_cpuhp_online); hv_cleanup(false); }; @@ -1340,6 +1340,7 @@ static void hv_crash_handler(struct pt_regs *regs) * doing the cleanup for current CPU only. This should be sufficient * for kdump. */ + vmbus_connection.conn_state = DISCONNECTED; hv_synic_cleanup(smp_processor_id()); hv_cleanup(true); }; @@ -1408,8 +1409,6 @@ static void __exit vmbus_exit(void) cpuhp_remove_state(hyperv_cpuhp_online); hv_synic_free(); acpi_bus_unregister_driver(&vmbus_acpi_driver); - if (vmbus_proto_version > VERSION_WIN7) - cpu_hotplug_enable(); } -- 2.7.4