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@xxxxxxxxxx>
---
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 | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 4d6b269..2e6b38e 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -32,6 +32,7 @@
#include <linux/completion.h>
#include <linux/hyperv.h>
#include <linux/kernel_stat.h>
+#include <linux/cpu.h>
#include <asm/hyperv.h>
#include <asm/hypervisor.h>
#include <asm/mshyperv.h>
@@ -671,6 +672,36 @@ static void vmbus_isr(void)
tasklet_schedule(&msg_dpc);
}
+#ifdef CONFIG_HOTPLUG_CPU
+static int hyperv_cpu_disable(void)
+{
+ return -1;
+}
+
+static void hv_cpu_hotplug_quirk(bool vmbus_loaded)
+{
+ /*
+ * 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) {
+ smp_ops.cpu_disable = hyperv_cpu_disable;
+ pr_notice("CPU offlining is not supported by hypervisor");
+ } else
+ smp_ops.cpu_disable = native_cpu_disable;
+}
+#else
+static void hv_cpu_hotplug_quirk(bool vmbus_loaded)
+{
+}
+#endif
+
/*
* vmbus_bus_init -Main vmbus driver initialization routine.
*
@@ -711,6 +742,7 @@ static int vmbus_bus_init(int irq)
if (ret)
goto err_alloc;
+ hv_cpu_hotplug_quirk(true);
vmbus_request_offers();
return 0;
@@ -964,6 +996,7 @@ 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
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