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Commit e513229b authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Greg Kroah-Hartman
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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: 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 c517d838

drivers/hv/vmbus_drv.c

+36 −0
Original line number Diff line number Diff line
@@ -33,6 +33,7 @@ 
#include <linux/hyperv.h>

#include <linux/kernel_stat.h>

#include <linux/clockchips.h>

#include <linux/cpu.h>

#include <asm/hyperv.h>

#include <asm/hypervisor.h>

#include <asm/mshyperv.h>
@@ -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);

}