mm: fix exec activate_mm vs TLB shootdown and lazy tlb switching race

[linux/fpc-iii.git] / arch / x86 / xen / enlighten.c

#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
#include <linux/bootmem.h>
#endif
#include <linux/cpu.h>
#include <linux/kexec.h>
#include <linux/slab.h>

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

#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>
#include <asm/cpu.h>
#include <asm/e820/api.h> 

#include "xen-ops.h"
#include "smp.h"
#include "pmu.h"

EXPORT_SYMBOL_GPL(hypercall_page);

/*
 * Pointer to the xen_vcpu_info structure or
 * &HYPERVISOR_shared_info->vcpu_info[cpu]. See xen_hvm_init_shared_info
 * and xen_vcpu_setup for details. By default it points to share_info->vcpu_info
 * but if the hypervisor supports VCPUOP_register_vcpu_info then it can point
 * to xen_vcpu_info. The pointer is used in __xen_evtchn_do_upcall to
 * acknowledge pending events.
 * Also more subtly it is used by the patched version of irq enable/disable
 * e.g. xen_irq_enable_direct and xen_iret in PV mode.
 *
 * The desire to be able to do those mask/unmask operations as a single
 * instruction by using the per-cpu offset held in %gs is the real reason
 * vcpu info is in a per-cpu pointer and the original reason for this
 * hypercall.
 *
 */
DEFINE_PER_CPU(struct vcpu_info *, xen_vcpu);

/*
 * Per CPU pages used if hypervisor supports VCPUOP_register_vcpu_info
 * hypercall. This can be used both in PV and PVHVM mode. The structure
 * overrides the default per_cpu(xen_vcpu, cpu) value.
 */
DEFINE_PER_CPU(struct vcpu_info, xen_vcpu_info);

/* Linux <-> Xen vCPU id mapping */
DEFINE_PER_CPU(uint32_t, xen_vcpu_id);
EXPORT_PER_CPU_SYMBOL(xen_vcpu_id);

enum xen_domain_type xen_domain_type = XEN_NATIVE;
EXPORT_SYMBOL_GPL(xen_domain_type);

unsigned long *machine_to_phys_mapping = (void *)MACH2PHYS_VIRT_START;
EXPORT_SYMBOL(machine_to_phys_mapping);
unsigned long  machine_to_phys_nr;
EXPORT_SYMBOL(machine_to_phys_nr);

struct start_info *xen_start_info;
EXPORT_SYMBOL_GPL(xen_start_info);

struct shared_info xen_dummy_shared_info;

__read_mostly int xen_have_vector_callback;
EXPORT_SYMBOL_GPL(xen_have_vector_callback);

/*
 * Point at some empty memory to start with. We map the real shared_info
 * page as soon as fixmap is up and running.
 */
struct shared_info *HYPERVISOR_shared_info = &xen_dummy_shared_info;

/*
 * Flag to determine whether vcpu info placement is available on all
 * VCPUs.  We assume it is to start with, and then set it to zero on
 * the first failure.  This is because it can succeed on some VCPUs
 * and not others, since it can involve hypervisor memory allocation,
 * or because the guest failed to guarantee all the appropriate
 * constraints on all VCPUs (ie buffer can't cross a page boundary).
 *
 * Note that any particular CPU may be using a placed vcpu structure,
 * but we can only optimise if the all are.
 *
 * 0: not available, 1: available
 */
int xen_have_vcpu_info_placement = 1;

static int xen_cpu_up_online(unsigned int cpu)
{
        xen_init_lock_cpu(cpu);
        return 0;
}

int xen_cpuhp_setup(int (*cpu_up_prepare_cb)(unsigned int),
                    int (*cpu_dead_cb)(unsigned int))
{
        int rc;

        rc = cpuhp_setup_state_nocalls(CPUHP_XEN_PREPARE,
                                       "x86/xen/guest:prepare",
                                       cpu_up_prepare_cb, cpu_dead_cb);
        if (rc >= 0) {
                rc = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
                                               "x86/xen/guest:online",
                                               xen_cpu_up_online, NULL);
                if (rc < 0)
                        cpuhp_remove_state_nocalls(CPUHP_XEN_PREPARE);
        }

        return rc >= 0 ? 0 : rc;
}

static int xen_vcpu_setup_restore(int cpu)
{
        int rc = 0;

        /* Any per_cpu(xen_vcpu) is stale, so reset it */
        xen_vcpu_info_reset(cpu);

        /*
         * For PVH and PVHVM, setup online VCPUs only. The rest will
         * be handled by hotplug.
         */
        if (xen_pv_domain() ||
            (xen_hvm_domain() && cpu_online(cpu))) {
                rc = xen_vcpu_setup(cpu);
        }

        return rc;
}

/*
 * On restore, set the vcpu placement up again.
 * If it fails, then we're in a bad state, since
 * we can't back out from using it...
 */
void xen_vcpu_restore(void)
{
        int cpu, rc;

        for_each_possible_cpu(cpu) {
                bool other_cpu = (cpu != smp_processor_id());
                bool is_up;

                if (xen_vcpu_nr(cpu) == XEN_VCPU_ID_INVALID)
                        continue;

                /* Only Xen 4.5 and higher support this. */
                is_up = HYPERVISOR_vcpu_op(VCPUOP_is_up,
                                           xen_vcpu_nr(cpu), NULL) > 0;

                if (other_cpu && is_up &&
                    HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL))
                        BUG();

                if (xen_pv_domain() || xen_feature(XENFEAT_hvm_safe_pvclock))
                        xen_setup_runstate_info(cpu);

                rc = xen_vcpu_setup_restore(cpu);
                if (rc)
                        pr_emerg_once("vcpu restore failed for cpu=%d err=%d. "
                                        "System will hang.\n", cpu, rc);
                /*
                 * In case xen_vcpu_setup_restore() fails, do not bring up the
                 * VCPU. This helps us avoid the resulting OOPS when the VCPU
                 * accesses pvclock_vcpu_time via xen_vcpu (which is NULL.)
                 * Note that this does not improve the situation much -- now the
                 * VM hangs instead of OOPSing -- with the VCPUs that did not
                 * fail, spinning in stop_machine(), waiting for the failed
                 * VCPUs to come up.
                 */
                if (other_cpu && is_up && (rc == 0) &&
                    HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL))
                        BUG();
        }
}

void xen_vcpu_info_reset(int cpu)
{
        if (xen_vcpu_nr(cpu) < MAX_VIRT_CPUS) {
                per_cpu(xen_vcpu, cpu) =
                        &HYPERVISOR_shared_info->vcpu_info[xen_vcpu_nr(cpu)];
        } else {
                /* Set to NULL so that if somebody accesses it we get an OOPS */
                per_cpu(xen_vcpu, cpu) = NULL;
        }
}

int xen_vcpu_setup(int cpu)
{
        struct vcpu_register_vcpu_info info;
        int err;
        struct vcpu_info *vcpup;

        BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);

        /*
         * This path is called on PVHVM at bootup (xen_hvm_smp_prepare_boot_cpu)
         * and at restore (xen_vcpu_restore). Also called for hotplugged
         * VCPUs (cpu_init -> xen_hvm_cpu_prepare_hvm).
         * However, the hypercall can only be done once (see below) so if a VCPU
         * is offlined and comes back online then let's not redo the hypercall.
         *
         * For PV it is called during restore (xen_vcpu_restore) and bootup
         * (xen_setup_vcpu_info_placement). The hotplug mechanism does not
         * use this function.
         */
        if (xen_hvm_domain()) {
                if (per_cpu(xen_vcpu, cpu) == &per_cpu(xen_vcpu_info, cpu))
                        return 0;
        }

        if (xen_have_vcpu_info_placement) {
                vcpup = &per_cpu(xen_vcpu_info, cpu);
                info.mfn = arbitrary_virt_to_mfn(vcpup);
                info.offset = offset_in_page(vcpup);

                /*
                 * Check to see if the hypervisor will put the vcpu_info
                 * structure where we want it, which allows direct access via
                 * a percpu-variable.
                 * N.B. This hypercall can _only_ be called once per CPU.
                 * Subsequent calls will error out with -EINVAL. This is due to
                 * the fact that hypervisor has no unregister variant and this
                 * hypercall does not allow to over-write info.mfn and
                 * info.offset.
                 */
                err = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_info,
                                         xen_vcpu_nr(cpu), &info);

                if (err) {
                        pr_warn_once("register_vcpu_info failed: cpu=%d err=%d\n",
                                     cpu, err);
                        xen_have_vcpu_info_placement = 0;
                } else {
                        /*
                         * This cpu is using the registered vcpu info, even if
                         * later ones fail to.
                         */
                        per_cpu(xen_vcpu, cpu) = vcpup;
                }
        }

        if (!xen_have_vcpu_info_placement)
                xen_vcpu_info_reset(cpu);

        return ((per_cpu(xen_vcpu, cpu) == NULL) ? -ENODEV : 0);
}

void xen_reboot(int reason)
{
        struct sched_shutdown r = { .reason = reason };
        int cpu;

        for_each_online_cpu(cpu)
                xen_pmu_finish(cpu);

        if (HYPERVISOR_sched_op(SCHEDOP_shutdown, &r))
                BUG();
}

static int reboot_reason = SHUTDOWN_reboot;
static bool xen_legacy_crash;
void xen_emergency_restart(void)
{
        xen_reboot(reboot_reason);
}

static int
xen_panic_event(struct notifier_block *this, unsigned long event, void *ptr)
{
        if (!kexec_crash_loaded()) {
                if (xen_legacy_crash)
                        xen_reboot(SHUTDOWN_crash);

                reboot_reason = SHUTDOWN_crash;

                /*
                 * If panic_timeout==0 then we are supposed to wait forever.
                 * However, to preserve original dom0 behavior we have to drop
                 * into hypervisor. (domU behavior is controlled by its
                 * config file)
                 */
                if (panic_timeout == 0)
                        panic_timeout = -1;
        }
        return NOTIFY_DONE;
}

static int __init parse_xen_legacy_crash(char *arg)
{
        xen_legacy_crash = true;
        return 0;
}
early_param("xen_legacy_crash", parse_xen_legacy_crash);

static struct notifier_block xen_panic_block = {
        .notifier_call = xen_panic_event,
        .priority = INT_MIN
};

int xen_panic_handler_init(void)
{
        atomic_notifier_chain_register(&panic_notifier_list, &xen_panic_block);
        return 0;
}

void xen_pin_vcpu(int cpu)
{
        static bool disable_pinning;
        struct sched_pin_override pin_override;
        int ret;

        if (disable_pinning)
                return;

        pin_override.pcpu = cpu;
        ret = HYPERVISOR_sched_op(SCHEDOP_pin_override, &pin_override);

        /* Ignore errors when removing override. */
        if (cpu < 0)
                return;

        switch (ret) {
        case -ENOSYS:
                pr_warn("Unable to pin on physical cpu %d. In case of problems consider vcpu pinning.\n",
                        cpu);
                disable_pinning = true;
                break;
        case -EPERM:
                WARN(1, "Trying to pin vcpu without having privilege to do so\n");
                disable_pinning = true;
                break;
        case -EINVAL:
        case -EBUSY:
                pr_warn("Physical cpu %d not available for pinning. Check Xen cpu configuration.\n",
                        cpu);
                break;
        case 0:
                break;
        default:
                WARN(1, "rc %d while trying to pin vcpu\n", ret);
                disable_pinning = true;
        }
}

#ifdef CONFIG_HOTPLUG_CPU
void xen_arch_register_cpu(int num)
{
        arch_register_cpu(num);
}
EXPORT_SYMBOL(xen_arch_register_cpu);

void xen_arch_unregister_cpu(int num)
{
        arch_unregister_cpu(num);
}
EXPORT_SYMBOL(xen_arch_unregister_cpu);
#endif