| Message ID | 1460484484-22395-18-git-send-email-luis.henriques@canonical.com |
|---|---|
| State | New |
| Headers | show |
On Tue, 2016-04-12 at 19:08 +0100, Luis Henriques wrote: > 3.16.7-ckt27 -stable review patch. If anyone has any objections, please let me know. > > ---8<------------------------------------------------------------ > > From: Vitaly Kuznetsov <vkuznets@redhat.com> > > commit e513229b4c386e6c9f66298c13fde92f73e6e1ac upstream. > > 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. [...] > +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; [...] This is a really bad hack. What if two different drivers patched smp_ops and got unloaded in a different order? Perhaps the core support code for Hyper-V should define its own smp_ops. I don't want to stop this going into stable, but seriously, please clean this up. Ben.
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 4d6b26979fbd..233da0b9f4b9 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 +672,39 @@ static void vmbus_isr(void) tasklet_schedule(&msg_dpc); } +#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. * @@ -711,6 +745,7 @@ static int vmbus_bus_init(int irq) if (ret) goto err_alloc; + hv_cpu_hotplug_quirk(true); vmbus_request_offers(); return 0; @@ -964,6 +999,7 @@ static void __exit vmbus_exit(void) bus_unregister(&hv_bus); hv_cleanup(); acpi_bus_unregister_driver(&vmbus_acpi_driver); + hv_cpu_hotplug_quirk(false); }