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From: KY Srinivasan <kys@microsoft.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>,
	"devel@linuxdriverproject.org" <devel@linuxdriverproject.org>
Cc: Haiyang Zhang <haiyangz@microsoft.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Dexuan Cui <decui@microsoft.com>
Subject: RE: [PATCH v3] Drivers: hv: vmbus: prevent cpu offlining on newer hypervisors
Date: Mon, 12 Jan 2015 18:54:13 +0000	[thread overview]
Message-ID: <BY2PR0301MB07113924DEAAE3D776AC44E7A0430@BY2PR0301MB0711.namprd03.prod.outlook.com> (raw)
In-Reply-To: <1421081411-5759-1-git-send-email-vkuznets@redhat.com>



> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@redhat.com]
> Sent: Monday, January 12, 2015 8:50 AM
> To: KY Srinivasan; devel@linuxdriverproject.org
> Cc: Haiyang Zhang; Greg Kroah-Hartman; linux-kernel@vger.kernel.org;
> Dexuan Cui
> Subject: [PATCH v3] 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: Vitaly Kuznetsov <vkuznets@redhat.com>
Thank you.
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> ---
> Changes since v2:
> - repair the build when vmbus is builded as a module [Greg KH] by saving
>   current cpu_disable pointer to previous_cpu_disable and restoring it on
>   unload;
> - return -ENOSYS (same as native_cpu_disable when
> !CONFIG_HOTPLUG_CPU) instead
>   of -1 in hyperv_cpu_disable().
> 
> 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 | 36 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
> 
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 4d6b269..233da0b 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);
>  }
> 
> 
> --
> 1.9.3


  reply	other threads:[~2015-01-12 18:54 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-11-26 13:52 [PATCH] " Vitaly Kuznetsov
2014-11-27  3:02 ` Greg Kroah-Hartman
2014-11-27  3:24   ` Dexuan Cui
2014-11-27  9:52     ` Vitaly Kuznetsov
2014-12-01 10:52 ` [PATCH v2] " Vitaly Kuznetsov
2014-12-01 11:12   ` Dexuan Cui
2015-01-09 20:57   ` Greg Kroah-Hartman
2015-01-12 16:50   ` [PATCH v3] " Vitaly Kuznetsov
2015-01-12 18:54     ` KY Srinivasan [this message]
2015-01-25 13:36     ` Greg Kroah-Hartman
2015-01-26 10:38       ` Vitaly Kuznetsov
2015-01-26 16:11         ` KY Srinivasan
2015-01-26 22:54         ` Greg Kroah-Hartman
2015-01-26 23:53           ` KY Srinivasan

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