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enlighten.c

/*
 * Core of Xen paravirt_ops implementation.
 *
 * This file contains the xen_paravirt_ops structure itself, and the
 * implementations for:
 * - privileged instructions
 * - interrupt flags
 * - segment operations
 * - booting and setup
 *
 * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/preempt.h>
#include <linux/hardirq.h>
#include <linux/percpu.h>
#include <linux/delay.h>
#include <linux/start_kernel.h>
#include <linux/sched.h>
#include <linux/bootmem.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/page-flags.h>
#include <linux/highmem.h>

#include <xen/interface/xen.h>
#include <xen/interface/physdev.h>
#include <xen/interface/vcpu.h>
#include <xen/interface/sched.h>
#include <xen/features.h>
#include <xen/page.h>

#include <asm/paravirt.h>
#include <asm/page.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>
#include <asm/fixmap.h>
#include <asm/processor.h>
#include <asm/setup.h>
#include <asm/desc.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
#include <asm/reboot.h>

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

EXPORT_SYMBOL_GPL(hypercall_page);

DEFINE_PER_CPU(struct vcpu_info *, xen_vcpu);
DEFINE_PER_CPU(struct vcpu_info, xen_vcpu_info);

/*
 * Note about cr3 (pagetable base) values:
 *
 * xen_cr3 contains the current logical cr3 value; it contains the
 * last set cr3.  This may not be the current effective cr3, because
 * its update may be being lazily deferred.  However, a vcpu looking
 * at its own cr3 can use this value knowing that it everything will
 * be self-consistent.
 *
 * xen_current_cr3 contains the actual vcpu cr3; it is set once the
 * hypercall to set the vcpu cr3 is complete (so it may be a little
 * out of date, but it will never be set early).  If one vcpu is
 * looking at another vcpu's cr3 value, it should use this variable.
 */
DEFINE_PER_CPU(unsigned long, xen_cr3);    /* cr3 stored as physaddr */
DEFINE_PER_CPU(unsigned long, xen_current_cr3);  /* actual vcpu cr3 */

struct start_info *xen_start_info;
EXPORT_SYMBOL_GPL(xen_start_info);

static /* __initdata */ struct shared_info dummy_shared_info;

/*
 * 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 = (void *)&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
 */
static int have_vcpu_info_placement = 0;

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

      per_cpu(xen_vcpu, cpu) = &HYPERVISOR_shared_info->vcpu_info[cpu];

      if (!have_vcpu_info_placement)
            return;           /* already tested, not available */

      vcpup = &per_cpu(xen_vcpu_info, cpu);

      info.mfn = virt_to_mfn(vcpup);
      info.offset = offset_in_page(vcpup);

      printk(KERN_DEBUG "trying to map vcpu_info %d at %p, mfn %llx, offset %d\n",
             cpu, vcpup, info.mfn, info.offset);

      /* Check to see if the hypervisor will put the vcpu_info
         structure where we want it, which allows direct access via
         a percpu-variable. */
      err = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_info, cpu, &info);

      if (err) {
            printk(KERN_DEBUG "register_vcpu_info failed: err=%d\n", err);
            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;

            printk(KERN_DEBUG "cpu %d using vcpu_info at %p\n",
                   cpu, vcpup);
      }
}

static void __init xen_banner(void)
{
      printk(KERN_INFO "Booting paravirtualized kernel on %s\n",
             pv_info.name);
      printk(KERN_INFO "Hypervisor signature: %s\n", xen_start_info->magic);
}

static void xen_cpuid(unsigned int *eax, unsigned int *ebx,
                  unsigned int *ecx, unsigned int *edx)
{
      unsigned maskedx = ~0;

      /*
       * Mask out inconvenient features, to try and disable as many
       * unsupported kernel subsystems as possible.
       */
      if (*eax == 1)
            maskedx = ~((1 << X86_FEATURE_APIC) |  /* disable APIC */
                      (1 << X86_FEATURE_ACPI) |  /* disable ACPI */
                      (1 << X86_FEATURE_ACC));   /* thermal monitoring */

      asm(XEN_EMULATE_PREFIX "cpuid"
            : "=a" (*eax),
              "=b" (*ebx),
              "=c" (*ecx),
              "=d" (*edx)
            : "0" (*eax), "2" (*ecx));
      *edx &= maskedx;
}

static void xen_set_debugreg(int reg, unsigned long val)
{
      HYPERVISOR_set_debugreg(reg, val);
}

static unsigned long xen_get_debugreg(int reg)
{
      return HYPERVISOR_get_debugreg(reg);
}

static unsigned long xen_save_fl(void)
{
      struct vcpu_info *vcpu;
      unsigned long flags;

      vcpu = x86_read_percpu(xen_vcpu);

      /* flag has opposite sense of mask */
      flags = !vcpu->evtchn_upcall_mask;

      /* convert to IF type flag
         -0 -> 0x00000000
         -1 -> 0xffffffff
      */
      return (-flags) & X86_EFLAGS_IF;
}

static void xen_restore_fl(unsigned long flags)
{
      struct vcpu_info *vcpu;

      /* convert from IF type flag */
      flags = !(flags & X86_EFLAGS_IF);

      /* There's a one instruction preempt window here.  We need to
         make sure we're don't switch CPUs between getting the vcpu
         pointer and updating the mask. */
      preempt_disable();
      vcpu = x86_read_percpu(xen_vcpu);
      vcpu->evtchn_upcall_mask = flags;
      preempt_enable_no_resched();

      /* Doesn't matter if we get preempted here, because any
         pending event will get dealt with anyway. */

      if (flags == 0) {
            preempt_check_resched();
            barrier(); /* unmask then check (avoid races) */
            if (unlikely(vcpu->evtchn_upcall_pending))
                  force_evtchn_callback();
      }
}

static void xen_irq_disable(void)
{
      /* There's a one instruction preempt window here.  We need to
         make sure we're don't switch CPUs between getting the vcpu
         pointer and updating the mask. */
      preempt_disable();
      x86_read_percpu(xen_vcpu)->evtchn_upcall_mask = 1;
      preempt_enable_no_resched();
}

static void xen_irq_enable(void)
{
      struct vcpu_info *vcpu;

      /* There's a one instruction preempt window here.  We need to
         make sure we're don't switch CPUs between getting the vcpu
         pointer and updating the mask. */
      preempt_disable();
      vcpu = x86_read_percpu(xen_vcpu);
      vcpu->evtchn_upcall_mask = 0;
      preempt_enable_no_resched();

      /* Doesn't matter if we get preempted here, because any
         pending event will get dealt with anyway. */

      barrier(); /* unmask then check (avoid races) */
      if (unlikely(vcpu->evtchn_upcall_pending))
            force_evtchn_callback();
}

static void xen_safe_halt(void)
{
      /* Blocking includes an implicit local_irq_enable(). */
      if (HYPERVISOR_sched_op(SCHEDOP_block, 0) != 0)
            BUG();
}

static void xen_halt(void)
{
      if (irqs_disabled())
            HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
      else
            xen_safe_halt();
}

static void xen_leave_lazy(void)
{
      paravirt_leave_lazy(paravirt_get_lazy_mode());
      xen_mc_flush();
}

static unsigned long xen_store_tr(void)
{
      return 0;
}

static void xen_set_ldt(const void *addr, unsigned entries)
{
      unsigned long linear_addr = (unsigned long)addr;
      struct mmuext_op *op;
      struct multicall_space mcs = xen_mc_entry(sizeof(*op));

      op = mcs.args;
      op->cmd = MMUEXT_SET_LDT;
      if (linear_addr) {
            /* ldt my be vmalloced, use arbitrary_virt_to_machine */
            xmaddr_t maddr;
            maddr = arbitrary_virt_to_machine((unsigned long)addr);
            linear_addr = (unsigned long)maddr.maddr;
      }
      op->arg1.linear_addr = linear_addr;
      op->arg2.nr_ents = entries;

      MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF);

      xen_mc_issue(PARAVIRT_LAZY_CPU);
}

static void xen_load_gdt(const struct Xgt_desc_struct *dtr)
{
      unsigned long *frames;
      unsigned long va = dtr->address;
      unsigned int size = dtr->size + 1;
      unsigned pages = (size + PAGE_SIZE - 1) / PAGE_SIZE;
      int f;
      struct multicall_space mcs;

      /* A GDT can be up to 64k in size, which corresponds to 8192
         8-byte entries, or 16 4k pages.. */

      BUG_ON(size > 65536);
      BUG_ON(va & ~PAGE_MASK);

      mcs = xen_mc_entry(sizeof(*frames) * pages);
      frames = mcs.args;

      for (f = 0; va < dtr->address + size; va += PAGE_SIZE, f++) {
            frames[f] = virt_to_mfn(va);
            make_lowmem_page_readonly((void *)va);
      }

      MULTI_set_gdt(mcs.mc, frames, size / sizeof(struct desc_struct));

      xen_mc_issue(PARAVIRT_LAZY_CPU);
}

static void load_TLS_descriptor(struct thread_struct *t,
                        unsigned int cpu, unsigned int i)
{
      struct desc_struct *gdt = get_cpu_gdt_table(cpu);
      xmaddr_t maddr = virt_to_machine(&gdt[GDT_ENTRY_TLS_MIN+i]);
      struct multicall_space mc = __xen_mc_entry(0);

      MULTI_update_descriptor(mc.mc, maddr.maddr, t->tls_array[i]);
}

static void xen_load_tls(struct thread_struct *t, unsigned int cpu)
{
      xen_mc_batch();

      load_TLS_descriptor(t, cpu, 0);
      load_TLS_descriptor(t, cpu, 1);
      load_TLS_descriptor(t, cpu, 2);

      xen_mc_issue(PARAVIRT_LAZY_CPU);

      /*
       * XXX sleazy hack: If we're being called in a lazy-cpu zone,
       * it means we're in a context switch, and %gs has just been
       * saved.  This means we can zero it out to prevent faults on
       * exit from the hypervisor if the next process has no %gs.
       * Either way, it has been saved, and the new value will get
       * loaded properly.  This will go away as soon as Xen has been
       * modified to not save/restore %gs for normal hypercalls.
       */
      if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_CPU)
            loadsegment(gs, 0);
}

static void xen_write_ldt_entry(struct desc_struct *dt, int entrynum,
                        u32 low, u32 high)
{
      unsigned long lp = (unsigned long)&dt[entrynum];
      xmaddr_t mach_lp = virt_to_machine(lp);
      u64 entry = (u64)high << 32 | low;

      preempt_disable();

      xen_mc_flush();
      if (HYPERVISOR_update_descriptor(mach_lp.maddr, entry))
            BUG();

      preempt_enable();
}

static int cvt_gate_to_trap(int vector, u32 low, u32 high,
                      struct trap_info *info)
{
      u8 type, dpl;

      type = (high >> 8) & 0x1f;
      dpl = (high >> 13) & 3;

      if (type != 0xf && type != 0xe)
            return 0;

      info->vector = vector;
      info->address = (high & 0xffff0000) | (low & 0x0000ffff);
      info->cs = low >> 16;
      info->flags = dpl;
      /* interrupt gates clear IF */
      if (type == 0xe)
            info->flags |= 4;

      return 1;
}

/* Locations of each CPU's IDT */
static DEFINE_PER_CPU(struct Xgt_desc_struct, idt_desc);

/* Set an IDT entry.  If the entry is part of the current IDT, then
   also update Xen. */
static void xen_write_idt_entry(struct desc_struct *dt, int entrynum,
                        u32 low, u32 high)
{
      unsigned long p = (unsigned long)&dt[entrynum];
      unsigned long start, end;

      preempt_disable();

      start = __get_cpu_var(idt_desc).address;
      end = start + __get_cpu_var(idt_desc).size + 1;

      xen_mc_flush();

      write_dt_entry(dt, entrynum, low, high);

      if (p >= start && (p + 8) <= end) {
            struct trap_info info[2];

            info[1].address = 0;

            if (cvt_gate_to_trap(entrynum, low, high, &info[0]))
                  if (HYPERVISOR_set_trap_table(info))
                        BUG();
      }

      preempt_enable();
}

static void xen_convert_trap_info(const struct Xgt_desc_struct *desc,
                          struct trap_info *traps)
{
      unsigned in, out, count;

      count = (desc->size+1) / 8;
      BUG_ON(count > 256);

      for (in = out = 0; in < count; in++) {
            const u32 *entry = (u32 *)(desc->address + in * 8);

            if (cvt_gate_to_trap(in, entry[0], entry[1], &traps[out]))
                  out++;
      }
      traps[out].address = 0;
}

void xen_copy_trap_info(struct trap_info *traps)
{
      const struct Xgt_desc_struct *desc = &__get_cpu_var(idt_desc);

      xen_convert_trap_info(desc, traps);
}

/* Load a new IDT into Xen.  In principle this can be per-CPU, so we
   hold a spinlock to protect the static traps[] array (static because
   it avoids allocation, and saves stack space). */
static void xen_load_idt(const struct Xgt_desc_struct *desc)
{
      static DEFINE_SPINLOCK(lock);
      static struct trap_info traps[257];

      spin_lock(&lock);

      __get_cpu_var(idt_desc) = *desc;

      xen_convert_trap_info(desc, traps);

      xen_mc_flush();
      if (HYPERVISOR_set_trap_table(traps))
            BUG();

      spin_unlock(&lock);
}

/* Write a GDT descriptor entry.  Ignore LDT descriptors, since
   they're handled differently. */
static void xen_write_gdt_entry(struct desc_struct *dt, int entry,
                        u32 low, u32 high)
{
      preempt_disable();

      switch ((high >> 8) & 0xff) {
      case DESCTYPE_LDT:
      case DESCTYPE_TSS:
            /* ignore */
            break;

      default: {
            xmaddr_t maddr = virt_to_machine(&dt[entry]);
            u64 desc = (u64)high << 32 | low;

            xen_mc_flush();
            if (HYPERVISOR_update_descriptor(maddr.maddr, desc))
                  BUG();
      }

      }

      preempt_enable();
}

static void xen_load_esp0(struct tss_struct *tss,
                    struct thread_struct *thread)
{
      struct multicall_space mcs = xen_mc_entry(0);
      MULTI_stack_switch(mcs.mc, __KERNEL_DS, thread->esp0);
      xen_mc_issue(PARAVIRT_LAZY_CPU);
}

static void xen_set_iopl_mask(unsigned mask)
{
      struct physdev_set_iopl set_iopl;

      /* Force the change at ring 0. */
      set_iopl.iopl = (mask == 0) ? 1 : (mask >> 12) & 3;
      HYPERVISOR_physdev_op(PHYSDEVOP_set_iopl, &set_iopl);
}

static void xen_io_delay(void)
{
}

#ifdef CONFIG_X86_LOCAL_APIC
static unsigned long xen_apic_read(unsigned long reg)
{
      return 0;
}

static void xen_apic_write(unsigned long reg, unsigned long val)
{
      /* Warn to see if there's any stray references */
      WARN_ON(1);
}
#endif

static void xen_flush_tlb(void)
{
      struct mmuext_op *op;
      struct multicall_space mcs = xen_mc_entry(sizeof(*op));

      op = mcs.args;
      op->cmd = MMUEXT_TLB_FLUSH_LOCAL;
      MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF);

      xen_mc_issue(PARAVIRT_LAZY_MMU);
}

static void xen_flush_tlb_single(unsigned long addr)
{
      struct mmuext_op *op;
      struct multicall_space mcs = xen_mc_entry(sizeof(*op));

      op = mcs.args;
      op->cmd = MMUEXT_INVLPG_LOCAL;
      op->arg1.linear_addr = addr & PAGE_MASK;
      MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF);

      xen_mc_issue(PARAVIRT_LAZY_MMU);
}

static void xen_flush_tlb_others(const cpumask_t *cpus, struct mm_struct *mm,
                         unsigned long va)
{
      struct {
            struct mmuext_op op;
            cpumask_t mask;
      } *args;
      cpumask_t cpumask = *cpus;
      struct multicall_space mcs;

      /*
       * A couple of (to be removed) sanity checks:
       *
       * - current CPU must not be in mask
       * - mask must exist :)
       */
      BUG_ON(cpus_empty(cpumask));
      BUG_ON(cpu_isset(smp_processor_id(), cpumask));
      BUG_ON(!mm);

      /* If a CPU which we ran on has gone down, OK. */
      cpus_and(cpumask, cpumask, cpu_online_map);
      if (cpus_empty(cpumask))
            return;

      mcs = xen_mc_entry(sizeof(*args));
      args = mcs.args;
      args->mask = cpumask;
      args->op.arg2.vcpumask = &args->mask;

      if (va == TLB_FLUSH_ALL) {
            args->op.cmd = MMUEXT_TLB_FLUSH_MULTI;
      } else {
            args->op.cmd = MMUEXT_INVLPG_MULTI;
            args->op.arg1.linear_addr = va;
      }

      MULTI_mmuext_op(mcs.mc, &args->op, 1, NULL, DOMID_SELF);

      xen_mc_issue(PARAVIRT_LAZY_MMU);
}

static void xen_write_cr2(unsigned long cr2)
{
      x86_read_percpu(xen_vcpu)->arch.cr2 = cr2;
}

static unsigned long xen_read_cr2(void)
{
      return x86_read_percpu(xen_vcpu)->arch.cr2;
}

static unsigned long xen_read_cr2_direct(void)
{
      return x86_read_percpu(xen_vcpu_info.arch.cr2);
}

static void xen_write_cr4(unsigned long cr4)
{
      /* Just ignore cr4 changes; Xen doesn't allow us to do
         anything anyway. */
}

static unsigned long xen_read_cr3(void)
{
      return x86_read_percpu(xen_cr3);
}

static void set_current_cr3(void *v)
{
      x86_write_percpu(xen_current_cr3, (unsigned long)v);
}

static void xen_write_cr3(unsigned long cr3)
{
      struct mmuext_op *op;
      struct multicall_space mcs;
      unsigned long mfn = pfn_to_mfn(PFN_DOWN(cr3));

      BUG_ON(preemptible());

      mcs = xen_mc_entry(sizeof(*op));  /* disables interrupts */

      /* Update while interrupts are disabled, so its atomic with
         respect to ipis */
      x86_write_percpu(xen_cr3, cr3);

      op = mcs.args;
      op->cmd = MMUEXT_NEW_BASEPTR;
      op->arg1.mfn = mfn;

      MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF);

      /* Update xen_update_cr3 once the batch has actually
         been submitted. */
      xen_mc_callback(set_current_cr3, (void *)cr3);

      xen_mc_issue(PARAVIRT_LAZY_CPU);  /* interrupts restored */
}

/* Early in boot, while setting up the initial pagetable, assume
   everything is pinned. */
static __init void xen_alloc_pt_init(struct mm_struct *mm, u32 pfn)
{
      BUG_ON(mem_map);  /* should only be used early */
      make_lowmem_page_readonly(__va(PFN_PHYS(pfn)));
}

static void pin_pagetable_pfn(unsigned level, unsigned long pfn)
{
      struct mmuext_op op;
      op.cmd = level;
      op.arg1.mfn = pfn_to_mfn(pfn);
      if (HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF))
            BUG();
}

/* This needs to make sure the new pte page is pinned iff its being
   attached to a pinned pagetable. */
static void xen_alloc_pt(struct mm_struct *mm, u32 pfn)
{
      struct page *page = pfn_to_page(pfn);

      if (PagePinned(virt_to_page(mm->pgd))) {
            SetPagePinned(page);

            if (!PageHighMem(page)) {
                  make_lowmem_page_readonly(__va(PFN_PHYS(pfn)));
                  pin_pagetable_pfn(MMUEXT_PIN_L1_TABLE, pfn);
            } else
                  /* make sure there are no stray mappings of
                     this page */
                  kmap_flush_unused();
      }
}

/* This should never happen until we're OK to use struct page */
static void xen_release_pt(u32 pfn)
{
      struct page *page = pfn_to_page(pfn);

      if (PagePinned(page)) {
            if (!PageHighMem(page)) {
                  pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, pfn);
                  make_lowmem_page_readwrite(__va(PFN_PHYS(pfn)));
            }
      }
}

#ifdef CONFIG_HIGHPTE
static void *xen_kmap_atomic_pte(struct page *page, enum km_type type)
{
      pgprot_t prot = PAGE_KERNEL;

      if (PagePinned(page))
            prot = PAGE_KERNEL_RO;

      if (0 && PageHighMem(page))
            printk("mapping highpte %lx type %d prot %s\n",
                   page_to_pfn(page), type,
                   (unsigned long)pgprot_val(prot) & _PAGE_RW ? "WRITE" : "READ");

      return kmap_atomic_prot(page, type, prot);
}
#endif

static __init pte_t mask_rw_pte(pte_t *ptep, pte_t pte)
{
      /* If there's an existing pte, then don't allow _PAGE_RW to be set */
      if (pte_val_ma(*ptep) & _PAGE_PRESENT)
            pte = __pte_ma(((pte_val_ma(*ptep) & _PAGE_RW) | ~_PAGE_RW) &
                         pte_val_ma(pte));

      return pte;
}

/* Init-time set_pte while constructing initial pagetables, which
   doesn't allow RO pagetable pages to be remapped RW */
static __init void xen_set_pte_init(pte_t *ptep, pte_t pte)
{
      pte = mask_rw_pte(ptep, pte);

      xen_set_pte(ptep, pte);
}

static __init void xen_pagetable_setup_start(pgd_t *base)
{
      pgd_t *xen_pgd = (pgd_t *)xen_start_info->pt_base;

      /* special set_pte for pagetable initialization */
      pv_mmu_ops.set_pte = xen_set_pte_init;

      init_mm.pgd = base;
      /*
       * copy top-level of Xen-supplied pagetable into place.      For
       * !PAE we can use this as-is, but for PAE it is a stand-in
       * while we copy the pmd pages.
       */
      memcpy(base, xen_pgd, PTRS_PER_PGD * sizeof(pgd_t));

      if (PTRS_PER_PMD > 1) {
            int i;
            /*
             * For PAE, need to allocate new pmds, rather than
             * share Xen's, since Xen doesn't like pmd's being
             * shared between address spaces.
             */
            for (i = 0; i < PTRS_PER_PGD; i++) {
                  if (pgd_val_ma(xen_pgd[i]) & _PAGE_PRESENT) {
                        pmd_t *pmd = (pmd_t *)alloc_bootmem_low_pages(PAGE_SIZE);

                        memcpy(pmd, (void *)pgd_page_vaddr(xen_pgd[i]),
                               PAGE_SIZE);

                        make_lowmem_page_readonly(pmd);

                        set_pgd(&base[i], __pgd(1 + __pa(pmd)));
                  } else
                        pgd_clear(&base[i]);
            }
      }

      /* make sure zero_page is mapped RO so we can use it in pagetables */
      make_lowmem_page_readonly(empty_zero_page);
      make_lowmem_page_readonly(base);
      /*
       * Switch to new pagetable.  This is done before
       * pagetable_init has done anything so that the new pages
       * added to the table can be prepared properly for Xen.
       */
      xen_write_cr3(__pa(base));
}

static __init void xen_pagetable_setup_done(pgd_t *base)
{
      /* This will work as long as patching hasn't happened yet
         (which it hasn't) */
      pv_mmu_ops.alloc_pt = xen_alloc_pt;
      pv_mmu_ops.set_pte = xen_set_pte;

      if (!xen_feature(XENFEAT_auto_translated_physmap)) {
            /*
             * Create a mapping for the shared info page.
             * Should be set_fixmap(), but shared_info is a machine
             * address with no corresponding pseudo-phys address.
             */
            set_pte_mfn(fix_to_virt(FIX_PARAVIRT_BOOTMAP),
                      PFN_DOWN(xen_start_info->shared_info),
                      PAGE_KERNEL);

            HYPERVISOR_shared_info =
                  (struct shared_info *)fix_to_virt(FIX_PARAVIRT_BOOTMAP);

      } else
            HYPERVISOR_shared_info =
                  (struct shared_info *)__va(xen_start_info->shared_info);

      /* Actually pin the pagetable down, but we can't set PG_pinned
         yet because the page structures don't exist yet. */
      {
            unsigned level;

#ifdef CONFIG_X86_PAE
            level = MMUEXT_PIN_L3_TABLE;
#else
            level = MMUEXT_PIN_L2_TABLE;
#endif

            pin_pagetable_pfn(level, PFN_DOWN(__pa(base)));
      }
}

/* This is called once we have the cpu_possible_map */
void __init xen_setup_vcpu_info_placement(void)
{
      int cpu;

      for_each_possible_cpu(cpu)
            xen_vcpu_setup(cpu);

      /* xen_vcpu_setup managed to place the vcpu_info within the
         percpu area for all cpus, so make use of it */
      if (have_vcpu_info_placement) {
            printk(KERN_INFO "Xen: using vcpu_info placement\n");

            pv_irq_ops.save_fl = xen_save_fl_direct;
            pv_irq_ops.restore_fl = xen_restore_fl_direct;
            pv_irq_ops.irq_disable = xen_irq_disable_direct;
            pv_irq_ops.irq_enable = xen_irq_enable_direct;
            pv_mmu_ops.read_cr2 = xen_read_cr2_direct;
            pv_cpu_ops.iret = xen_iret_direct;
      }
}

static unsigned xen_patch(u8 type, u16 clobbers, void *insnbuf,
                    unsigned long addr, unsigned len)
{
      char *start, *end, *reloc;
      unsigned ret;

      start = end = reloc = NULL;

#define SITE(op, x)                                         \
      case PARAVIRT_PATCH(op.x):                            \
      if (have_vcpu_info_placement) {                             \
            start = (char *)xen_##x##_direct;               \
            end = xen_##x##_direct_end;                     \
            reloc = xen_##x##_direct_reloc;                       \
      }                                               \
      goto patch_site

      switch (type) {
            SITE(pv_irq_ops, irq_enable);
            SITE(pv_irq_ops, irq_disable);
            SITE(pv_irq_ops, save_fl);
            SITE(pv_irq_ops, restore_fl);
#undef SITE

      patch_site:
            if (start == NULL || (end-start) > len)
                  goto default_patch;

            ret = paravirt_patch_insns(insnbuf, len, start, end);

            /* Note: because reloc is assigned from something that
               appears to be an array, gcc assumes it's non-null,
               but doesn't know its relationship with start and
               end. */
            if (reloc > start && reloc < end) {
                  int reloc_off = reloc - start;
                  long *relocp = (long *)(insnbuf + reloc_off);
                  long delta = start - (char *)addr;

                  *relocp += delta;
            }
            break;

      default_patch:
      default:
            ret = paravirt_patch_default(type, clobbers, insnbuf,
                                   addr, len);
            break;
      }

      return ret;
}

static const struct pv_info xen_info __initdata = {
      .paravirt_enabled = 1,
      .shared_kernel_pmd = 0,

      .name = "Xen",
};

static const struct pv_init_ops xen_init_ops __initdata = {
      .patch = xen_patch,

      .banner = xen_banner,
      .memory_setup = xen_memory_setup,
      .arch_setup = xen_arch_setup,
      .post_allocator_init = xen_mark_init_mm_pinned,
};

static const struct pv_time_ops xen_time_ops __initdata = {
      .time_init = xen_time_init,

      .set_wallclock = xen_set_wallclock,
      .get_wallclock = xen_get_wallclock,
      .get_cpu_khz = xen_cpu_khz,
      .sched_clock = xen_sched_clock,
};

static const struct pv_cpu_ops xen_cpu_ops __initdata = {
      .cpuid = xen_cpuid,

      .set_debugreg = xen_set_debugreg,
      .get_debugreg = xen_get_debugreg,

      .clts = native_clts,

      .read_cr0 = native_read_cr0,
      .write_cr0 = native_write_cr0,

      .read_cr4 = native_read_cr4,
      .read_cr4_safe = native_read_cr4_safe,
      .write_cr4 = xen_write_cr4,

      .wbinvd = native_wbinvd,

      .read_msr = native_read_msr_safe,
      .write_msr = native_write_msr_safe,
      .read_tsc = native_read_tsc,
      .read_pmc = native_read_pmc,

      .iret = (void *)&hypercall_page[__HYPERVISOR_iret],
      .irq_enable_sysexit = NULL,  /* never called */

      .load_tr_desc = paravirt_nop,
      .set_ldt = xen_set_ldt,
      .load_gdt = xen_load_gdt,
      .load_idt = xen_load_idt,
      .load_tls = xen_load_tls,

      .store_gdt = native_store_gdt,
      .store_idt = native_store_idt,
      .store_tr = xen_store_tr,

      .write_ldt_entry = xen_write_ldt_entry,
      .write_gdt_entry = xen_write_gdt_entry,
      .write_idt_entry = xen_write_idt_entry,
      .load_esp0 = xen_load_esp0,

      .set_iopl_mask = xen_set_iopl_mask,
      .io_delay = xen_io_delay,

      .lazy_mode = {
            .enter = paravirt_enter_lazy_cpu,
            .leave = xen_leave_lazy,
      },
};

static const struct pv_irq_ops xen_irq_ops __initdata = {
      .init_IRQ = xen_init_IRQ,
      .save_fl = xen_save_fl,
      .restore_fl = xen_restore_fl,
      .irq_disable = xen_irq_disable,
      .irq_enable = xen_irq_enable,
      .safe_halt = xen_safe_halt,
      .halt = xen_halt,
};

static const struct pv_apic_ops xen_apic_ops __initdata = {
#ifdef CONFIG_X86_LOCAL_APIC
      .apic_write = xen_apic_write,
      .apic_write_atomic = xen_apic_write,
      .apic_read = xen_apic_read,
      .setup_boot_clock = paravirt_nop,
      .setup_secondary_clock = paravirt_nop,
      .startup_ipi_hook = paravirt_nop,
#endif
};

static const struct pv_mmu_ops xen_mmu_ops __initdata = {
      .pagetable_setup_start = xen_pagetable_setup_start,
      .pagetable_setup_done = xen_pagetable_setup_done,

      .read_cr2 = xen_read_cr2,
      .write_cr2 = xen_write_cr2,

      .read_cr3 = xen_read_cr3,
      .write_cr3 = xen_write_cr3,

      .flush_tlb_user = xen_flush_tlb,
      .flush_tlb_kernel = xen_flush_tlb,
      .flush_tlb_single = xen_flush_tlb_single,
      .flush_tlb_others = xen_flush_tlb_others,

      .pte_update = paravirt_nop,
      .pte_update_defer = paravirt_nop,

      .alloc_pt = xen_alloc_pt_init,
      .release_pt = xen_release_pt,
      .alloc_pd = paravirt_nop,
      .alloc_pd_clone = paravirt_nop,
      .release_pd = paravirt_nop,

#ifdef CONFIG_HIGHPTE
      .kmap_atomic_pte = xen_kmap_atomic_pte,
#endif

      .set_pte = NULL,  /* see xen_pagetable_setup_* */
      .set_pte_at = xen_set_pte_at,
      .set_pmd = xen_set_pmd,

      .pte_val = xen_pte_val,
      .pgd_val = xen_pgd_val,

      .make_pte = xen_make_pte,
      .make_pgd = xen_make_pgd,

#ifdef CONFIG_X86_PAE
      .set_pte_atomic = xen_set_pte_atomic,
      .set_pte_present = xen_set_pte_at,
      .set_pud = xen_set_pud,
      .pte_clear = xen_pte_clear,
      .pmd_clear = xen_pmd_clear,

      .make_pmd = xen_make_pmd,
      .pmd_val = xen_pmd_val,
#endif      /* PAE */

      .activate_mm = xen_activate_mm,
      .dup_mmap = xen_dup_mmap,
      .exit_mmap = xen_exit_mmap,

      .lazy_mode = {
            .enter = paravirt_enter_lazy_mmu,
            .leave = xen_leave_lazy,
      },
};

#ifdef CONFIG_SMP
static const struct smp_ops xen_smp_ops __initdata = {
      .smp_prepare_boot_cpu = xen_smp_prepare_boot_cpu,
      .smp_prepare_cpus = xen_smp_prepare_cpus,
      .cpu_up = xen_cpu_up,
      .smp_cpus_done = xen_smp_cpus_done,

      .smp_send_stop = xen_smp_send_stop,
      .smp_send_reschedule = xen_smp_send_reschedule,
      .smp_call_function_mask = xen_smp_call_function_mask,
};
#endif      /* CONFIG_SMP */

static void xen_reboot(int reason)
{
#ifdef CONFIG_SMP
      smp_send_stop();
#endif

      if (HYPERVISOR_sched_op(SCHEDOP_shutdown, reason))
            BUG();
}

static void xen_restart(char *msg)
{
      xen_reboot(SHUTDOWN_reboot);
}

static void xen_emergency_restart(void)
{
      xen_reboot(SHUTDOWN_reboot);
}

static void xen_machine_halt(void)
{
      xen_reboot(SHUTDOWN_poweroff);
}

static void xen_crash_shutdown(struct pt_regs *regs)
{
      xen_reboot(SHUTDOWN_crash);
}

static const struct machine_ops __initdata xen_machine_ops = {
      .restart = xen_restart,
      .halt = xen_machine_halt,
      .power_off = xen_machine_halt,
      .shutdown = xen_machine_halt,
      .crash_shutdown = xen_crash_shutdown,
      .emergency_restart = xen_emergency_restart,
};


static void __init xen_reserve_top(void)
{
      unsigned long top = HYPERVISOR_VIRT_START;
      struct xen_platform_parameters pp;

      if (HYPERVISOR_xen_version(XENVER_platform_parameters, &pp) == 0)
            top = pp.virt_start;

      reserve_top_address(-top + 2 * PAGE_SIZE);
}

/* First C function to be called on Xen boot */
asmlinkage void __init xen_start_kernel(void)
{
      pgd_t *pgd;

      if (!xen_start_info)
            return;

      BUG_ON(memcmp(xen_start_info->magic, "xen-3", 5) != 0);

      /* Install Xen paravirt ops */
      pv_info = xen_info;
      pv_init_ops = xen_init_ops;
      pv_time_ops = xen_time_ops;
      pv_cpu_ops = xen_cpu_ops;
      pv_irq_ops = xen_irq_ops;
      pv_apic_ops = xen_apic_ops;
      pv_mmu_ops = xen_mmu_ops;

      machine_ops = xen_machine_ops;

#ifdef CONFIG_SMP
      smp_ops = xen_smp_ops;
#endif

      xen_setup_features();

      /* Get mfn list */
      if (!xen_feature(XENFEAT_auto_translated_physmap))
            phys_to_machine_mapping = (unsigned long *)xen_start_info->mfn_list;

      pgd = (pgd_t *)xen_start_info->pt_base;

      init_pg_tables_end = __pa(pgd) + xen_start_info->nr_pt_frames*PAGE_SIZE;

      init_mm.pgd = pgd; /* use the Xen pagetables to start */

      /* keep using Xen gdt for now; no urgent need to change it */

      x86_write_percpu(xen_cr3, __pa(pgd));
      x86_write_percpu(xen_current_cr3, __pa(pgd));

#ifdef CONFIG_SMP
      /* Don't do the full vcpu_info placement stuff until we have a
         possible map. */
      per_cpu(xen_vcpu, 0) = &HYPERVISOR_shared_info->vcpu_info[0];
#else
      /* May as well do it now, since there's no good time to call
         it later on UP. */
      xen_setup_vcpu_info_placement();
#endif

      pv_info.kernel_rpl = 1;
      if (xen_feature(XENFEAT_supervisor_mode_kernel))
            pv_info.kernel_rpl = 0;

      /* set the limit of our address space */
      xen_reserve_top();

      /* set up basic CPUID stuff */
      cpu_detect(&new_cpu_data);
      new_cpu_data.hard_math = 1;
      new_cpu_data.x86_capability[0] = cpuid_edx(1);

      /* Poke various useful things into boot_params */
      boot_params.hdr.type_of_loader = (9 << 4) | 0;
      boot_params.hdr.ramdisk_image = xen_start_info->mod_start
            ? __pa(xen_start_info->mod_start) : 0;
      boot_params.hdr.ramdisk_size = xen_start_info->mod_len;

      /* Start the world */
      start_kernel();
}

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