xen: SMP guest support
This is a fairly straightforward Xen implementation of smp_ops.
Xen has its own IPI mechanisms, and has no dependency on any
APIC-based IPI. The smp_ops hooks and the flush_tlb_others pv_op
allow a Xen guest to avoid all APIC code in arch/i386 (the only apic
operation is a single apic_read for the apic version number).
One subtle point which needs to be addressed is unpinning pagetables
when another cpu may have a lazy tlb reference to the pagetable. Xen
will not allow an in-use pagetable to be unpinned, so we must find any
other cpus with a reference to the pagetable and get them to shoot
down their references.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Andi Kleen <ak@suse.de>
diff --git a/arch/i386/xen/smp.c b/arch/i386/xen/smp.c
new file mode 100644
index 0000000..a91587f
--- /dev/null
+++ b/arch/i386/xen/smp.c
@@ -0,0 +1,407 @@
+/*
+ * 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();
+
+ xen_vcpu_setup(0);
+
+ /* 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 (cpu = 0; cpu < NR_CPUS; cpu++) {
+ cpus_clear(cpu_sibling_map[cpu]);
+ cpus_clear(cpu_core_map[cpu]);
+ }
+}
+
+void __init xen_smp_prepare_cpus(unsigned int max_cpus)
+{
+ unsigned cpu;
+
+ for (cpu = 0; cpu < NR_CPUS; cpu++) {
+ cpus_clear(cpu_sibling_map[cpu]);
+ cpus_clear(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.esp0 - sizeof(struct pt_regs);
+
+ ctxt->kernel_ss = __KERNEL_DS;
+ ctxt->kernel_sp = idle->thread.esp0;
+
+ 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;
+ xen_vcpu_setup(cpu);
+ 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)
+{
+ cpumask_t mask = cpu_online_map;
+ cpu_clear(smp_processor_id(), mask);
+ xen_smp_call_function_mask(mask, stop_self, NULL, 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);
+ 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;
+
+ /* 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.
+ XXX too severe? Maybe we should check the other CPU's states? */
+ 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;
+}