smp.c

/*
 * Xen SMP support
 *
 * This file implements the Xen versions of smp_ops.  SMP under Xen is
 * very straightforward.  Bringing a CPU up is simply a matter of
 * loading its initial context and setting it running.
 *
 * IPIs are handled through the Xen event mechanism.
 *
 * Because virtual CPUs can be scheduled onto any real CPU, there's no
 * useful topology information for the kernel to make use of.  As a
 * result, all CPUs are treated as if they're single-core and
 * single-threaded.
 *
 * This does not handle HOTPLUG_CPU yet.
 */
#include <linux/sched.h>
#include <linux/err.h>
#include <linux/smp.h>

#include <asm/paravirt.h>
#include <asm/desc.h>
#include <asm/pgtable.h>
#include <asm/cpu.h>

#include <xen/interface/xen.h>
#include <xen/interface/vcpu.h>

#include <asm/xen/interface.h>
#include <asm/xen/hypercall.h>

#include <xen/page.h>
#include <xen/events.h>

#include "xen-ops.h"
#include "mmu.h"

static cpumask_t cpu_initialized_map;
static DEFINE_PER_CPU(int, resched_irq);
static DEFINE_PER_CPU(int, callfunc_irq);

/*
 * Structure and data for smp_call_function(). This is designed to minimise
 * static memory requirements. It also looks cleaner.
 */
static DEFINE_SPINLOCK(call_lock);

struct call_data_struct {
	void (*func) (void *info);
	void *info;
	atomic_t started;
	atomic_t finished;
	int wait;
};

static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id);

static struct call_data_struct *call_data;

/*
 * Reschedule call back. Nothing to do,
 * all the work is done automatically when
 * we return from the interrupt.
 */
static irqreturn_t xen_reschedule_interrupt(int irq, void *dev_id)
{
	return IRQ_HANDLED;
}

static __cpuinit void cpu_bringup_and_idle(void)
{
	int cpu = smp_processor_id();

	cpu_init();

	preempt_disable();
	per_cpu(cpu_state, cpu) = CPU_ONLINE;

	xen_setup_cpu_clockevents();

	/* We can take interrupts now: we're officially "up". */
	local_irq_enable();

	wmb();			/* make sure everything is out */
	cpu_idle();
}

static int xen_smp_intr_init(unsigned int cpu)
{
	int rc;
	const char *resched_name, *callfunc_name;

	per_cpu(resched_irq, cpu) = per_cpu(callfunc_irq, cpu) = -1;

	resched_name = kasprintf(GFP_KERNEL, "resched%d", cpu);
	rc = bind_ipi_to_irqhandler(XEN_RESCHEDULE_VECTOR,
				    cpu,
				    xen_reschedule_interrupt,
				    IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
				    resched_name,
				    NULL);
	if (rc < 0)
		goto fail;
	per_cpu(resched_irq, cpu) = rc;

	callfunc_name = kasprintf(GFP_KERNEL, "callfunc%d", cpu);
	rc = bind_ipi_to_irqhandler(XEN_CALL_FUNCTION_VECTOR,
				    cpu,
				    xen_call_function_interrupt,
				    IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
				    callfunc_name,
				    NULL);
	if (rc < 0)
		goto fail;
	per_cpu(callfunc_irq, cpu) = rc;

	return 0;

 fail:
	if (per_cpu(resched_irq, cpu) >= 0)
		unbind_from_irqhandler(per_cpu(resched_irq, cpu), NULL);
	if (per_cpu(callfunc_irq, cpu) >= 0)
		unbind_from_irqhandler(per_cpu(callfunc_irq, cpu), NULL);
	return rc;
}

void __init xen_fill_possible_map(void)
{
	int i, rc;

	for (i = 0; i < NR_CPUS; i++) {
		rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
		if (rc >= 0)
			cpu_set(i, cpu_possible_map);
	}
}

void __init xen_smp_prepare_boot_cpu(void)
{
	int cpu;

	BUG_ON(smp_processor_id() != 0);
	native_smp_prepare_boot_cpu();

	/* We've switched to the "real" per-cpu gdt, so make sure the
	   old memory can be recycled */
	make_lowmem_page_readwrite(&per_cpu__gdt_page);

	for_each_possible_cpu(cpu) {
		cpus_clear(per_cpu(cpu_sibling_map, cpu));
		/*
		 * cpu_core_map lives in a per cpu area that is cleared
		 * when the per cpu array is allocated.
		 *
		 * cpus_clear(per_cpu(cpu_core_map, cpu));
		 */
	}

	xen_setup_vcpu_info_placement();
}

void __init xen_smp_prepare_cpus(unsigned int max_cpus)
{
	unsigned cpu;

	for_each_possible_cpu(cpu) {
		cpus_clear(per_cpu(cpu_sibling_map, cpu));
		/*
		 * cpu_core_ map will be zeroed when the per
		 * cpu area is allocated.
		 *
		 * cpus_clear(per_cpu(cpu_core_map, cpu));
		 */
	}

	smp_store_cpu_info(0);
	set_cpu_sibling_map(0);

	if (xen_smp_intr_init(0))
		BUG();

	cpu_initialized_map = cpumask_of_cpu(0);

	/* Restrict the possible_map according to max_cpus. */
	while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
		for (cpu = NR_CPUS-1; !cpu_isset(cpu, cpu_possible_map); cpu--)
			continue;
		cpu_clear(cpu, cpu_possible_map);
	}

	for_each_possible_cpu (cpu) {
		struct task_struct *idle;

		if (cpu == 0)
			continue;

		idle = fork_idle(cpu);
		if (IS_ERR(idle))
			panic("failed fork for CPU %d", cpu);

		cpu_set(cpu, cpu_present_map);
	}

	//init_xenbus_allowed_cpumask();
}

static __cpuinit int
cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
{
	struct vcpu_guest_context *ctxt;
	struct gdt_page *gdt = &per_cpu(gdt_page, cpu);

	if (cpu_test_and_set(cpu, cpu_initialized_map))
		return 0;

	ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
	if (ctxt == NULL)
		return -ENOMEM;

	ctxt->flags = VGCF_IN_KERNEL;
	ctxt->user_regs.ds = __USER_DS;
	ctxt->user_regs.es = __USER_DS;
	ctxt->user_regs.fs = __KERNEL_PERCPU;
	ctxt->user_regs.gs = 0;
	ctxt->user_regs.ss = __KERNEL_DS;
	ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
	ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */

	memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));

	xen_copy_trap_info(ctxt->trap_ctxt);

	ctxt->ldt_ents = 0;

	BUG_ON((unsigned long)gdt->gdt & ~PAGE_MASK);
	make_lowmem_page_readonly(gdt->gdt);

	ctxt->gdt_frames[0] = virt_to_mfn(gdt->gdt);
	ctxt->gdt_ents      = ARRAY_SIZE(gdt->gdt);

	ctxt->user_regs.cs = __KERNEL_CS;
	ctxt->user_regs.esp = idle->thread.sp0 - sizeof(struct pt_regs);

	ctxt->kernel_ss = __KERNEL_DS;
	ctxt->kernel_sp = idle->thread.sp0;

	ctxt->event_callback_cs     = __KERNEL_CS;
	ctxt->event_callback_eip    = (unsigned long)xen_hypervisor_callback;
	ctxt->failsafe_callback_cs  = __KERNEL_CS;
	ctxt->failsafe_callback_eip = (unsigned long)xen_failsafe_callback;

	per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
	ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));

	if (HYPERVISOR_vcpu_op(VCPUOP_initialise, cpu, ctxt))
		BUG();

	kfree(ctxt);
	return 0;
}

int __cpuinit xen_cpu_up(unsigned int cpu)
{
	struct task_struct *idle = idle_task(cpu);
	int rc;

#if 0
	rc = cpu_up_check(cpu);
	if (rc)
		return rc;
#endif

	init_gdt(cpu);
	per_cpu(current_task, cpu) = idle;
	irq_ctx_init(cpu);
	xen_setup_timer(cpu);

	/* make sure interrupts start blocked */
	per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;

	rc = cpu_initialize_context(cpu, idle);
	if (rc)
		return rc;

	if (num_online_cpus() == 1)
		alternatives_smp_switch(1);

	rc = xen_smp_intr_init(cpu);
	if (rc)
		return rc;

	smp_store_cpu_info(cpu);
	set_cpu_sibling_map(cpu);
	/* This must be done before setting cpu_online_map */
	wmb();

	cpu_set(cpu, cpu_online_map);

	rc = HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL);
	BUG_ON(rc);

	return 0;
}

void xen_smp_cpus_done(unsigned int max_cpus)
{
}

static void stop_self(void *v)
{
	int cpu = smp_processor_id();

	/* make sure we're not pinning something down */
	load_cr3(swapper_pg_dir);
	/* should set up a minimal gdt */

	HYPERVISOR_vcpu_op(VCPUOP_down, cpu, NULL);
	BUG();
}

void xen_smp_send_stop(void)
{
	smp_call_function(stop_self, NULL, 0, 0);
}

void xen_smp_send_reschedule(int cpu)
{
	xen_send_IPI_one(cpu, XEN_RESCHEDULE_VECTOR);
}


static void xen_send_IPI_mask(cpumask_t mask, enum ipi_vector vector)
{
	unsigned cpu;

	cpus_and(mask, mask, cpu_online_map);

	for_each_cpu_mask(cpu, mask)
		xen_send_IPI_one(cpu, vector);
}

static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id)
{
	void (*func) (void *info) = call_data->func;
	void *info = call_data->info;
	int wait = call_data->wait;

	/*
	 * Notify initiating CPU that I've grabbed the data and am
	 * about to execute the function
	 */
	mb();
	atomic_inc(&call_data->started);
	/*
	 * At this point the info structure may be out of scope unless wait==1
	 */
	irq_enter();
	(*func)(info);
	__get_cpu_var(irq_stat).irq_call_count++;
	irq_exit();

	if (wait) {
		mb();		/* commit everything before setting finished */
		atomic_inc(&call_data->finished);
	}

	return IRQ_HANDLED;
}

int xen_smp_call_function_mask(cpumask_t mask, void (*func)(void *),
			       void *info, int wait)
{
	struct call_data_struct data;
	int cpus, cpu;
	bool yield;

	/* Holding any lock stops cpus from going down. */
	spin_lock(&call_lock);

	cpu_clear(smp_processor_id(), mask);

	cpus = cpus_weight(mask);
	if (!cpus) {
		spin_unlock(&call_lock);
		return 0;
	}

	/* Can deadlock when called with interrupts disabled */
	WARN_ON(irqs_disabled());

	data.func = func;
	data.info = info;
	atomic_set(&data.started, 0);
	data.wait = wait;
	if (wait)
		atomic_set(&data.finished, 0);

	call_data = &data;
	mb();			/* write everything before IPI */

	/* Send a message to other CPUs and wait for them to respond */
	xen_send_IPI_mask(mask, XEN_CALL_FUNCTION_VECTOR);

	/* Make sure other vcpus get a chance to run if they need to. */
	yield = false;
	for_each_cpu_mask(cpu, mask)
		if (xen_vcpu_stolen(cpu))
			yield = true;

	if (yield)
		HYPERVISOR_sched_op(SCHEDOP_yield, 0);

	/* Wait for response */
	while (atomic_read(&data.started) != cpus ||
	       (wait && atomic_read(&data.finished) != cpus))
		cpu_relax();

	spin_unlock(&call_lock);

	return 0;
}