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: Jiang, Yunhong <yunhong.jiang@intel.com>
Signed-off-by: Liu, Jinsong <jinsong.liu@intel.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

2 files changed, 372 insertions, 0 deletions

diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile
index a7870292bc75..d80bea5535a2 100644
--- a/drivers/xen/Makefile
+++ b/drivers/xen/Makefile
@@ -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/
diff --git a/drivers/xen/pcpu.c b/drivers/xen/pcpu.c
new file mode 100644
index 000000000000..067fcfa1723e
--- /dev/null
+++ b/drivers/xen/pcpu.c
@@ -0,0 +1,371 @@
+/******************************************************************************
+ * 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);