// SPDX-License-Identifier: GPL-2.0
/*
 * 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.
 */
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/smp.h>
#include <linux/irq_work.h>
#include <linux/tick.h>
#include <linux/nmi.h>
#include <linux/cpuhotplug.h>
#include <linux/stackprotector.h>
#include <linux/pgtable.h>

#include <asm/paravirt.h>
#include <asm/idtentry.h>
#include <asm/desc.h>
#include <asm/cpu.h>
#include <asm/apic.h>
#include <asm/io_apic.h>

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

#include <asm/spec-ctrl.h>
#include <asm/xen/interface.h>
#include <asm/xen/hypercall.h>

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

#include <xen/hvc-console.h>
#include "xen-ops.h"

cpumask_var_t xen_cpu_initialized_map;

static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 };
static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 };

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

static void cpu_bringup(void)
{
        int cpu;

        cr4_init();
        cpuhp_ap_sync_alive();
        cpu_init();
        fpu__init_cpu();
        touch_softlockup_watchdog();

        /* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
        if (!xen_feature(XENFEAT_supervisor_mode_kernel))
                xen_enable_syscall();

        cpu = smp_processor_id();
        identify_secondary_cpu(cpu);
        set_cpu_sibling_map(cpu);

        speculative_store_bypass_ht_init();

        xen_setup_cpu_clockevents();

        notify_cpu_starting(cpu);

        set_cpu_online(cpu, true);

        smp_mb();

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

asmlinkage __visible void cpu_bringup_and_idle(void)
{
        cpu_bringup();
        cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
}

void xen_smp_intr_free_pv(unsigned int cpu)
{
        kfree(per_cpu(xen_irq_work, cpu).name);
        per_cpu(xen_irq_work, cpu).name = NULL;
        if (per_cpu(xen_irq_work, cpu).irq >= 0) {
                unbind_from_irqhandler(per_cpu(xen_irq_work, cpu).irq, NULL);
                per_cpu(xen_irq_work, cpu).irq = -1;
        }

        kfree(per_cpu(xen_pmu_irq, cpu).name);
        per_cpu(xen_pmu_irq, cpu).name = NULL;
        if (per_cpu(xen_pmu_irq, cpu).irq >= 0) {
                unbind_from_irqhandler(per_cpu(xen_pmu_irq, cpu).irq, NULL);
                per_cpu(xen_pmu_irq, cpu).irq = -1;
        }
}

int xen_smp_intr_init_pv(unsigned int cpu)
{
        int rc;
        char *callfunc_name, *pmu_name;

        callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu);
        per_cpu(xen_irq_work, cpu).name = callfunc_name;
        rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
                                    cpu,
                                    xen_irq_work_interrupt,
                                    IRQF_PERCPU|IRQF_NOBALANCING,
                                    callfunc_name,
                                    NULL);
        if (rc < 0)
                goto fail;
        per_cpu(xen_irq_work, cpu).irq = rc;

        if (is_xen_pmu) {
                pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu);
                per_cpu(xen_pmu_irq, cpu).name = pmu_name;
                rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu,
                                             xen_pmu_irq_handler,
                                             IRQF_PERCPU|IRQF_NOBALANCING,
                                             pmu_name, NULL);
                if (rc < 0)
                        goto fail;
                per_cpu(xen_pmu_irq, cpu).irq = rc;
        }

        return 0;

 fail:
        xen_smp_intr_free_pv(cpu);
        return rc;
}

static void __init xen_pv_smp_config(void)
{
        u32 apicid = 0;
        int i;

        topology_register_boot_apic(apicid);

        for (i = 0; i < nr_cpu_ids; i++)
                topology_register_apic(apicid++, CPU_ACPIID_INVALID, true);

        /* Pretend to be a proper enumerated system */
        smp_found_config = 1;
}

static void __init xen_pv_smp_prepare_boot_cpu(void)
{
        BUG_ON(smp_processor_id() != 0);
        native_smp_prepare_boot_cpu();

        if (!xen_feature(XENFEAT_writable_page_tables))
                /* We've switched to the "real" per-cpu gdt, so make
                 * sure the old memory can be recycled. */
                make_lowmem_page_readwrite(xen_initial_gdt);

        xen_setup_vcpu_info_placement();

        /*
         * The alternative logic (which patches the unlock/lock) runs before
         * the smp bootup up code is activated. Hence we need to set this up
         * the core kernel is being patched. Otherwise we will have only
         * modules patched but not core code.
         */
        xen_init_spinlocks();
}

static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus)
{
        unsigned cpu;

        if (ioapic_is_disabled) {
                char *m = (max_cpus == 0) ?
                        "The nosmp parameter is incompatible with Xen; " \
                        "use Xen dom0_max_vcpus=1 parameter" :
                        "The noapic parameter is incompatible with Xen";

                xen_raw_printk(m);
                panic(m);
        }
        xen_init_lock_cpu(0);

        smp_prepare_cpus_common();

        speculative_store_bypass_ht_init();

        xen_pmu_init(0);

        if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
                BUG();

        if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
                panic("could not allocate xen_cpu_initialized_map\n");

        cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));

        /* Restrict the possible_map according to max_cpus. */
        while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
                for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
                        continue;
                set_cpu_possible(cpu, false);
        }

        for_each_possible_cpu(cpu)
                set_cpu_present(cpu, true);
}

static int
cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
{
        struct vcpu_guest_context *ctxt;
        struct desc_struct *gdt;
        unsigned long gdt_mfn;

        if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
                return 0;

        ctxt = kzalloc_obj(*ctxt);
        if (ctxt == NULL) {
                cpumask_clear_cpu(cpu, xen_cpu_initialized_map);
                return -ENOMEM;
        }

        gdt = get_cpu_gdt_rw(cpu);

        /*
         * Bring up the CPU in cpu_bringup_and_idle() with the stack
         * pointing just below where pt_regs would be if it were a normal
         * kernel entry.
         */
        ctxt->user_regs.eip = (unsigned long)asm_cpu_bringup_and_idle;
        ctxt->flags = VGCF_IN_KERNEL;
        ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
        ctxt->user_regs.ds = __USER_DS;
        ctxt->user_regs.es = __USER_DS;
        ctxt->user_regs.ss = __KERNEL_DS;
        ctxt->user_regs.cs = __KERNEL_CS;
        ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle);

        xen_copy_trap_info(ctxt->trap_ctxt);

        BUG_ON((unsigned long)gdt & ~PAGE_MASK);

        gdt_mfn = arbitrary_virt_to_mfn(gdt);
        make_lowmem_page_readonly(gdt);
        make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));

        ctxt->gdt_frames[0] = gdt_mfn;
        ctxt->gdt_ents      = GDT_ENTRIES;

        /*
         * Set SS:SP that Xen will use when entering guest kernel mode
         * from guest user mode.  Subsequent calls to load_sp0() can
         * change this value.
         */
        ctxt->kernel_ss = __KERNEL_DS;
        ctxt->kernel_sp = task_top_of_stack(idle);

        ctxt->gs_base_kernel = per_cpu_offset(cpu);
        ctxt->event_callback_eip    =
                (unsigned long)xen_asm_exc_xen_hypervisor_callback;
        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_gfn(swapper_pg_dir));
        if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
                BUG();

        kfree(ctxt);
        return 0;
}

static int xen_pv_kick_ap(unsigned int cpu, struct task_struct *idle)
{
        int rc;

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

        xen_setup_runstate_info(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;

        xen_pmu_init(cpu);

        /*
         * Why is this a BUG? If the hypercall fails then everything can be
         * rolled back, no?
         */
        BUG_ON(HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL));

        return 0;
}

static void xen_pv_poll_sync_state(void)
{
        HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
}

#ifdef CONFIG_HOTPLUG_CPU
static int xen_pv_cpu_disable(void)
{
        unsigned int cpu = smp_processor_id();
        if (cpu == 0)
                return -EBUSY;

        cpu_disable_common();

        load_cr3(swapper_pg_dir);
        return 0;
}

static void xen_pv_cpu_die(unsigned int cpu)
{
        while (HYPERVISOR_vcpu_op(VCPUOP_is_up, xen_vcpu_nr(cpu), NULL)) {
                __set_current_state(TASK_UNINTERRUPTIBLE);
                schedule_timeout(HZ/10);
        }
}

static void xen_pv_cleanup_dead_cpu(unsigned int cpu)
{
        xen_smp_intr_free(cpu);
        xen_uninit_lock_cpu(cpu);
        xen_teardown_timer(cpu);
        xen_pmu_finish(cpu);
}

static void __noreturn xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
{
        play_dead_common();
        HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL);
        xen_cpu_bringup_again((unsigned long)task_pt_regs(current));
        BUG();
}

#else /* !CONFIG_HOTPLUG_CPU */
static int xen_pv_cpu_disable(void)
{
        return -ENOSYS;
}

static void xen_pv_cpu_die(unsigned int cpu)
{
        BUG();
}

static void xen_pv_cleanup_dead_cpu(unsigned int cpu)
{
        BUG();
}

static void __noreturn xen_pv_play_dead(void)
{
        BUG();
}

#endif
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 */

        set_cpu_online(cpu, false);

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

static void xen_pv_stop_other_cpus(int wait)
{
        smp_call_function(stop_self, NULL, wait);
}

static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
{
        irq_work_run();
        inc_irq_stat(apic_irq_work_irqs);

        return IRQ_HANDLED;
}

void __init xen_smp_count_cpus(void)
{
        unsigned int cpus;

        for (cpus = 0; cpus < nr_cpu_ids; cpus++) {
                if (HYPERVISOR_vcpu_op(VCPUOP_is_up, cpus, NULL) < 0)
                        break;
        }

        pr_info("Xen PV: Detected %u vCPUS\n", cpus);
        if (cpus < nr_cpu_ids)
                set_nr_cpu_ids(cpus);
}

static const struct smp_ops xen_smp_ops __initconst = {
        .smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu,
        .smp_prepare_cpus = xen_pv_smp_prepare_cpus,
        .smp_cpus_done = xen_smp_cpus_done,

        .kick_ap_alive = xen_pv_kick_ap,
        .cpu_die = xen_pv_cpu_die,
        .cleanup_dead_cpu = xen_pv_cleanup_dead_cpu,
        .poll_sync_state = xen_pv_poll_sync_state,
        .cpu_disable = xen_pv_cpu_disable,
        .play_dead = xen_pv_play_dead,

        .stop_other_cpus = xen_pv_stop_other_cpus,
        .smp_send_reschedule = xen_smp_send_reschedule,

        .send_call_func_ipi = xen_smp_send_call_function_ipi,
        .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
};

void __init xen_smp_init(void)
{
        smp_ops = xen_smp_ops;

        /* Avoid searching for BIOS MP tables */
        x86_init.mpparse.find_mptable           = x86_init_noop;
        x86_init.mpparse.early_parse_smp_cfg    = x86_init_noop;

        /* XEN/PV Dom0 has halfways sane topology information via CPUID/MADT */
        if (xen_initial_domain())
                x86_init.mpparse.parse_smp_cfg  = x86_init_noop;
        else
                x86_init.mpparse.parse_smp_cfg  = xen_pv_smp_config;
}