Commit 523b9408 authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Greg Kroah-Hartman
Browse files

hv: make CPU offlining prevention fine-grained 



Since commit e513229b ("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: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: default avatarK. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 76d36ab7

drivers/hv/hv.c

+31 −0
Original line number Diff line number Diff line
@@ -587,10 +587,41 @@ 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);

drivers/hv/vmbus_drv.c

+4 −5
Original line number Diff line number Diff line
@@ -1008,9 +1008,6 @@ 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

	 */
@@ -1486,6 +1483,9 @@ 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);

};
@@ -1498,6 +1498,7 @@ 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);

};
@@ -1566,8 +1567,6 @@ 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();

}

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