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Drivers: hv: vmbus: prevent cpu offlining on newer hypervisors

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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 <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Vitaly Kuznetsov 2015-02-27 11:25:51 -08:00 committed by Greg Kroah-Hartman
parent c517d838eb
commit e513229b4c
1 changed files with 36 additions and 0 deletions
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36
drivers/hv/vmbus_drv.c
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@ -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);
}