Commit f65c9bb3 authored by Liu, Jinsong's avatar Liu, Jinsong Committed by Konrad Rzeszutek Wilk
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xen/pcpu: Xen physical cpus online/offline sys interface 



This patch provide Xen physical cpus online/offline sys interface.
User can use it for their own purpose, like power saving:
by offlining some cpus when light workload it save power greatly.

Its basic workflow is, user online/offline cpu via sys interface,
then hypercall xen to implement, after done xen inject virq back to dom0,
and then dom0 sync cpu status.

Signed-off-by: default avatarJiang, Yunhong <yunhong.jiang@intel.com>
Signed-off-by: default avatarLiu, Jinsong <jinsong.liu@intel.com>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 05e36006

Documentation/ABI/testing/sysfs-devices-system-xen_cpu

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What:		/sys/devices/system/xen_cpu/

Date:		May 2012

Contact:	Liu, Jinsong <jinsong.liu@intel.com>

Description:

		A collection of global/individual Xen physical cpu attributes



		Individual physical cpu attributes are contained in

		subdirectories named by the Xen's logical cpu number, e.g.:

		/sys/devices/system/xen_cpu/xen_cpu#/





What:		/sys/devices/system/xen_cpu/xen_cpu#/online

Date:		May 2012

Contact:	Liu, Jinsong <jinsong.liu@intel.com>

Description:

		Interface to online/offline Xen physical cpus



		When running under Xen platform, it provide user interface

		to online/offline physical cpus, except cpu0 due to several

		logic restrictions and assumptions.

drivers/xen/Makefile

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@@ -17,6 +17,7 @@ obj-$(CONFIG_XEN_SYS_HYPERVISOR) += sys-hypervisor.o 
obj-$(CONFIG_XEN_PVHVM)			+= platform-pci.o

obj-$(CONFIG_XEN_TMEM)			+= tmem.o

obj-$(CONFIG_SWIOTLB_XEN)		+= swiotlb-xen.o

obj-$(CONFIG_XEN_DOM0)			+= pcpu.o

obj-$(CONFIG_XEN_DOM0)			+= pci.o acpi.o

obj-$(CONFIG_XEN_MCE_LOG)		+= mcelog.o

obj-$(CONFIG_XEN_PCIDEV_BACKEND)	+= xen-pciback/

drivers/xen/pcpu.c

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Original line number Diff line number Diff line 
/******************************************************************************

 * pcpu.c

 * Management physical cpu in dom0, get pcpu info and provide sys interface

 *

 * Copyright (c) 2012 Intel Corporation

 * Author: Liu, Jinsong <jinsong.liu@intel.com>

 * Author: Jiang, Yunhong <yunhong.jiang@intel.com>

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of the GNU General Public License version 2

 * as published by the Free Software Foundation; or, when distributed

 * separately from the Linux kernel or incorporated into other

 * software packages, subject to the following license:

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this source file (the "Software"), to deal in the Software without

 * restriction, including without limitation the rights to use, copy, modify,

 * merge, publish, distribute, sublicense, and/or sell copies of the Software,

 * and to permit persons to whom the Software is furnished to do so, subject to

 * the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS

 * IN THE SOFTWARE.

 */



#include <linux/interrupt.h>

#include <linux/spinlock.h>

#include <linux/cpu.h>

#include <linux/stat.h>

#include <linux/capability.h>



#include <xen/xen.h>

#include <xen/xenbus.h>

#include <xen/events.h>

#include <xen/interface/platform.h>

#include <asm/xen/hypervisor.h>

#include <asm/xen/hypercall.h>



#define XEN_PCPU "xen_cpu: "



/*

 * @cpu_id: Xen physical cpu logic number

 * @flags: Xen physical cpu status flag

 * - XEN_PCPU_FLAGS_ONLINE: cpu is online

 * - XEN_PCPU_FLAGS_INVALID: cpu is not present

 */

struct pcpu {

	struct list_head list;

	struct device dev;

	uint32_t cpu_id;

	uint32_t flags;

};



static struct bus_type xen_pcpu_subsys = {

	.name = "xen_cpu",

	.dev_name = "xen_cpu",

};



static DEFINE_MUTEX(xen_pcpu_lock);



static LIST_HEAD(xen_pcpus);



static int xen_pcpu_down(uint32_t cpu_id)

{

	struct xen_platform_op op = {

		.cmd			= XENPF_cpu_offline,

		.interface_version	= XENPF_INTERFACE_VERSION,

		.u.cpu_ol.cpuid		= cpu_id,

	};



	return HYPERVISOR_dom0_op(&op);

}



static int xen_pcpu_up(uint32_t cpu_id)

{

	struct xen_platform_op op = {

		.cmd			= XENPF_cpu_online,

		.interface_version	= XENPF_INTERFACE_VERSION,

		.u.cpu_ol.cpuid		= cpu_id,

	};



	return HYPERVISOR_dom0_op(&op);

}



static ssize_t show_online(struct device *dev,

			   struct device_attribute *attr,

			   char *buf)

{

	struct pcpu *cpu = container_of(dev, struct pcpu, dev);



	return sprintf(buf, "%u\n", !!(cpu->flags & XEN_PCPU_FLAGS_ONLINE));

}



static ssize_t __ref store_online(struct device *dev,

				  struct device_attribute *attr,

				  const char *buf, size_t count)

{

	struct pcpu *pcpu = container_of(dev, struct pcpu, dev);

	unsigned long long val;

	ssize_t ret;



	if (!capable(CAP_SYS_ADMIN))

		return -EPERM;



	if (kstrtoull(buf, 0, &val) < 0)

		return -EINVAL;



	switch (val) {

	case 0:

		ret = xen_pcpu_down(pcpu->cpu_id);

		break;

	case 1:

		ret = xen_pcpu_up(pcpu->cpu_id);

		break;

	default:

		ret = -EINVAL;

	}



	if (ret >= 0)

		ret = count;

	return ret;

}

static DEVICE_ATTR(online, S_IRUGO | S_IWUSR, show_online, store_online);



static bool xen_pcpu_online(uint32_t flags)

{

	return !!(flags & XEN_PCPU_FLAGS_ONLINE);

}



static void pcpu_online_status(struct xenpf_pcpuinfo *info,

			       struct pcpu *pcpu)

{

	if (xen_pcpu_online(info->flags) &&

	   !xen_pcpu_online(pcpu->flags)) {

		/* the pcpu is onlined */

		pcpu->flags |= XEN_PCPU_FLAGS_ONLINE;

		kobject_uevent(&pcpu->dev.kobj, KOBJ_ONLINE);

	} else if (!xen_pcpu_online(info->flags) &&

		    xen_pcpu_online(pcpu->flags)) {

		/* The pcpu is offlined */

		pcpu->flags &= ~XEN_PCPU_FLAGS_ONLINE;

		kobject_uevent(&pcpu->dev.kobj, KOBJ_OFFLINE);

	}

}



static struct pcpu *get_pcpu(uint32_t cpu_id)

{

	struct pcpu *pcpu;



	list_for_each_entry(pcpu, &xen_pcpus, list) {

		if (pcpu->cpu_id == cpu_id)

			return pcpu;

	}



	return NULL;

}



static void pcpu_release(struct device *dev)

{

	struct pcpu *pcpu = container_of(dev, struct pcpu, dev);



	list_del(&pcpu->list);

	kfree(pcpu);

}



static void unregister_and_remove_pcpu(struct pcpu *pcpu)

{

	struct device *dev;



	if (!pcpu)

		return;



	dev = &pcpu->dev;

	if (dev->id)

		device_remove_file(dev, &dev_attr_online);



	/* pcpu remove would be implicitly done */

	device_unregister(dev);

}



static int register_pcpu(struct pcpu *pcpu)

{

	struct device *dev;

	int err = -EINVAL;



	if (!pcpu)

		return err;



	dev = &pcpu->dev;

	dev->bus = &xen_pcpu_subsys;

	dev->id = pcpu->cpu_id;

	dev->release = pcpu_release;



	err = device_register(dev);

	if (err) {

		pcpu_release(dev);

		return err;

	}



	/*

	 * Xen never offline cpu0 due to several restrictions

	 * and assumptions. This basically doesn't add a sys control

	 * to user, one cannot attempt to offline BSP.

	 */

	if (dev->id) {

		err = device_create_file(dev, &dev_attr_online);

		if (err) {

			device_unregister(dev);

			return err;

		}

	}



	return 0;

}



static struct pcpu *create_and_register_pcpu(struct xenpf_pcpuinfo *info)

{

	struct pcpu *pcpu;

	int err;



	if (info->flags & XEN_PCPU_FLAGS_INVALID)

		return ERR_PTR(-ENODEV);



	pcpu = kzalloc(sizeof(struct pcpu), GFP_KERNEL);

	if (!pcpu)

		return ERR_PTR(-ENOMEM);



	INIT_LIST_HEAD(&pcpu->list);

	pcpu->cpu_id = info->xen_cpuid;

	pcpu->flags = info->flags;



	/* Need hold on xen_pcpu_lock before pcpu list manipulations */

	list_add_tail(&pcpu->list, &xen_pcpus);



	err = register_pcpu(pcpu);

	if (err) {

		pr_warning(XEN_PCPU "Failed to register pcpu%u\n",

			   info->xen_cpuid);

		return ERR_PTR(-ENOENT);

	}



	return pcpu;

}



/*

 * Caller should hold the xen_pcpu_lock

 */

static int sync_pcpu(uint32_t cpu, uint32_t *max_cpu)

{

	int ret;

	struct pcpu *pcpu = NULL;

	struct xenpf_pcpuinfo *info;

	struct xen_platform_op op = {

		.cmd                   = XENPF_get_cpuinfo,

		.interface_version     = XENPF_INTERFACE_VERSION,

		.u.pcpu_info.xen_cpuid = cpu,

	};



	ret = HYPERVISOR_dom0_op(&op);

	if (ret)

		return ret;



	info = &op.u.pcpu_info;

	if (max_cpu)

		*max_cpu = info->max_present;



	pcpu = get_pcpu(cpu);



	/*

	 * Only those at cpu present map has its sys interface.

	 */

	if (info->flags & XEN_PCPU_FLAGS_INVALID) {

		if (pcpu)

			unregister_and_remove_pcpu(pcpu);

		return 0;

	}



	if (!pcpu) {

		pcpu = create_and_register_pcpu(info);

		if (IS_ERR_OR_NULL(pcpu))

			return -ENODEV;

	} else

		pcpu_online_status(info, pcpu);



	return 0;

}



/*

 * Sync dom0's pcpu information with xen hypervisor's

 */

static int xen_sync_pcpus(void)

{

	/*

	 * Boot cpu always have cpu_id 0 in xen

	 */

	uint32_t cpu = 0, max_cpu = 0;

	int err = 0;

	struct pcpu *pcpu, *tmp;



	mutex_lock(&xen_pcpu_lock);



	while (!err && (cpu <= max_cpu)) {

		err = sync_pcpu(cpu, &max_cpu);

		cpu++;

	}



	if (err)

		list_for_each_entry_safe(pcpu, tmp, &xen_pcpus, list)

			unregister_and_remove_pcpu(pcpu);



	mutex_unlock(&xen_pcpu_lock);



	return err;

}



static void xen_pcpu_work_fn(struct work_struct *work)

{

	xen_sync_pcpus();

}

static DECLARE_WORK(xen_pcpu_work, xen_pcpu_work_fn);



static irqreturn_t xen_pcpu_interrupt(int irq, void *dev_id)

{

	schedule_work(&xen_pcpu_work);

	return IRQ_HANDLED;

}



static int __init xen_pcpu_init(void)

{

	int irq, ret;



	if (!xen_initial_domain())

		return -ENODEV;



	irq = bind_virq_to_irqhandler(VIRQ_PCPU_STATE, 0,

				      xen_pcpu_interrupt, 0,

				      "xen-pcpu", NULL);

	if (irq < 0) {

		pr_warning(XEN_PCPU "Failed to bind pcpu virq\n");

		return irq;

	}



	ret = subsys_system_register(&xen_pcpu_subsys, NULL);

	if (ret) {

		pr_warning(XEN_PCPU "Failed to register pcpu subsys\n");

		goto err1;

	}



	ret = xen_sync_pcpus();

	if (ret) {

		pr_warning(XEN_PCPU "Failed to sync pcpu info\n");

		goto err2;

	}



	return 0;



err2:

	bus_unregister(&xen_pcpu_subsys);

err1:

	unbind_from_irqhandler(irq, NULL);

	return ret;

}

arch_initcall(xen_pcpu_init);

include/xen/interface/platform.h

+8 −0
Original line number Diff line number Diff line
@@ -314,6 +314,13 @@ struct xenpf_pcpuinfo { 
};

DEFINE_GUEST_HANDLE_STRUCT(xenpf_pcpuinfo);



#define XENPF_cpu_online	56

#define XENPF_cpu_offline	57

struct xenpf_cpu_ol {

	uint32_t cpuid;

};

DEFINE_GUEST_HANDLE_STRUCT(xenpf_cpu_ol);



struct xen_platform_op {

	uint32_t cmd;

	uint32_t interface_version; /* XENPF_INTERFACE_VERSION */
@@ -330,6 +337,7 @@ struct xen_platform_op { 
		struct xenpf_getidletime       getidletime;

		struct xenpf_set_processor_pminfo set_pminfo;

		struct xenpf_pcpuinfo          pcpu_info;

		struct xenpf_cpu_ol            cpu_ol;

		uint8_t                        pad[128];

	} u;

};

include/xen/interface/xen.h

+1 −0
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@@ -80,6 +80,7 @@ 
#define VIRQ_CONSOLE    2  /* (DOM0) Bytes received on emergency console. */

#define VIRQ_DOM_EXC    3  /* (DOM0) Exceptional event for some domain.   */

#define VIRQ_DEBUGGER   6  /* (DOM0) A domain has paused for debugging.   */

#define VIRQ_PCPU_STATE 9  /* (DOM0) PCPU state changed                   */



/* Architecture-specific VIRQ definitions. */

#define VIRQ_ARCH_0    16

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