text: /*
   * 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/cpu.h>
  #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/kprobes.h>
  #include <linux/bootmem.h>
  #include <linux/module.h>
  #include <linux/mm.h>
  #include <linux/page-flags.h>
  #include <linux/highmem.h>
  #include <linux/console.h>
  #include <linux/pci.h>
  #include <linux/gfp.h>
  #include <linux/memblock.h>
  #include <linux/edd.h>
  
  #ifdef CONFIG_KEXEC_CORE
  #include <linux/kexec.h>
  #endif
  
  #include <xen/xen.h>
  #include <xen/events.h>
  #include <xen/interface/xen.h>
  #include <xen/interface/version.h>
  #include <xen/interface/physdev.h>
  #include <xen/interface/vcpu.h>
  #include <xen/interface/memory.h>
  #include <xen/interface/nmi.h>
  #include <xen/interface/xen-mca.h>
  #include <xen/features.h>
  #include <xen/page.h>
  #include <xen/hvm.h>
  #include <xen/hvc-console.h>
  #include <xen/acpi.h>
  
  #include <asm/paravirt.h>
  #include <asm/apic.h>
  #include <asm/page.h>
  #include <asm/xen/pci.h>
  #include <asm/xen/hypercall.h>
  #include <asm/xen/hypervisor.h>
  #include <asm/fixmap.h>
  #include <asm/processor.h>
  #include <asm/proto.h>
  #include <asm/msr-index.h>
  #include <asm/traps.h>
  #include <asm/setup.h>
  #include <asm/desc.h>
  #include <asm/pgalloc.h>
  #include <asm/pgtable.h>
  #include <asm/tlbflush.h>
  #include <asm/reboot.h>
  #include <asm/stackprotector.h>
  #include <asm/hypervisor.h>
  #include <asm/mach_traps.h>
  #include <asm/mwait.h>
  #include <asm/pci_x86.h>
  #include <asm/pat.h>
  #include <asm/cpu.h>
  
  #ifdef CONFIG_ACPI
  #include <linux/acpi.h>
  #include <asm/acpi.h>
  #include <acpi/pdc_intel.h>
  #include <acpi/processor.h>
  #include <xen/interface/platform.h>
  #endif
  
  #include "xen-ops.h"
  #include "mmu.h"
  #include "smp.h"
  #include "multicalls.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);
  
  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;
  
  void *xen_initial_gdt;
  
  RESERVE_BRK(shared_info_page_brk, PAGE_SIZE);
  __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
   */
  static int have_vcpu_info_placement = 1;
  
  struct tls_descs {
  	struct desc_struct desc[3];
  };
  
  /*
   * Updating the 3 TLS descriptors in the GDT on every task switch is
   * surprisingly expensive so we avoid updating them if they haven't
   * changed.  Since Xen writes different descriptors than the one
   * passed in the update_descriptor hypercall we keep shadow copies to
   * compare against.
   */
  static DEFINE_PER_CPU(struct tls_descs, shadow_tls_desc);
  
  static void clamp_max_cpus(void)
  {
  #ifdef CONFIG_SMP
  	if (setup_max_cpus > MAX_VIRT_CPUS)
  		setup_max_cpus = MAX_VIRT_CPUS;
  #endif
  }
  
  static void 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 twice on PVHVM - first during bootup via
  	 * smp_init -> xen_hvm_cpu_notify, and then if the VCPU is being
  	 * hotplugged: cpu_up -> xen_hvm_cpu_notify.
  	 * As we can only do the VCPUOP_register_vcpu_info once lets
  	 * not over-write its result.
  	 *
  	 * 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;
  	}
  	if (cpu < MAX_VIRT_CPUS)
  		per_cpu(xen_vcpu,cpu) = &HYPERVISOR_shared_info->vcpu_info[cpu];
  
  	if (!have_vcpu_info_placement) {
  		if (cpu >= MAX_VIRT_CPUS)
  			clamp_max_cpus();
  		return;
  	}
  
  	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, cpu, &info);
  
  	if (err) {
  		printk(KERN_DEBUG "register_vcpu_info failed: err=%d\n", err);
  		have_vcpu_info_placement = 0;
  		clamp_max_cpus();
  	} else {
  		/* This cpu is using the registered vcpu info, even if
  		   later ones fail to. */
  		per_cpu(xen_vcpu, cpu) = vcpup;
  	}
  }
  
  /*
   * 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;
  
  	for_each_possible_cpu(cpu) {
  		bool other_cpu = (cpu != smp_processor_id());
  		bool is_up = HYPERVISOR_vcpu_op(VCPUOP_is_up, cpu, NULL);
  
  		if (other_cpu && is_up &&
  		    HYPERVISOR_vcpu_op(VCPUOP_down, cpu, NULL))
  			BUG();
  
  		xen_setup_runstate_info(cpu);
  
  		if (have_vcpu_info_placement)
  			xen_vcpu_setup(cpu);
  
  		if (other_cpu && is_up &&
  		    HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL))
  			BUG();
  	}
  }
  
  static void __init xen_banner(void)
  {
  	unsigned version = HYPERVISOR_xen_version(XENVER_version, NULL);
  	struct xen_extraversion extra;
  	HYPERVISOR_xen_version(XENVER_extraversion, &extra);
  
  	pr_info("Booting paravirtualized kernel %son %s\n",
  		xen_feature(XENFEAT_auto_translated_physmap) ?
  			"with PVH extensions " : "", pv_info.name);
  	printk(KERN_INFO "Xen version: %d.%d%s%s\n",
  	       version >> 16, version & 0xffff, extra.extraversion,
  	       xen_feature(XENFEAT_mmu_pt_update_preserve_ad) ? " (preserve-AD)" : "");
  }
  /* Check if running on Xen version (major, minor) or later */
  bool
  xen_running_on_version_or_later(unsigned int major, unsigned int minor)
  {
  	unsigned int version;
  
  	if (!xen_domain())
  		return false;
  
  	version = HYPERVISOR_xen_version(XENVER_version, NULL);
  	if ((((version >> 16) == major) && ((version & 0xffff) >= minor)) ||
  		((version >> 16) > major))
  		return true;
  	return false;
  }
  
  #define CPUID_THERM_POWER_LEAF 6
  #define APERFMPERF_PRESENT 0
  
  static __read_mostly unsigned int cpuid_leaf1_edx_mask = ~0;
  static __read_mostly unsigned int cpuid_leaf1_ecx_mask = ~0;
  
  static __read_mostly unsigned int cpuid_leaf1_ecx_set_mask;
  static __read_mostly unsigned int cpuid_leaf5_ecx_val;
  static __read_mostly unsigned int cpuid_leaf5_edx_val;
  
  static void xen_cpuid(unsigned int *ax, unsigned int *bx,
  		      unsigned int *cx, unsigned int *dx)
  {
  	unsigned maskebx = ~0;
  	unsigned maskecx = ~0;
  	unsigned maskedx = ~0;
  	unsigned setecx = 0;
  	/*
  	 * Mask out inconvenient features, to try and disable as many
  	 * unsupported kernel subsystems as possible.
  	 */
  	switch (*ax) {
  	case 1:
  		maskecx = cpuid_leaf1_ecx_mask;
  		setecx = cpuid_leaf1_ecx_set_mask;
  		maskedx = cpuid_leaf1_edx_mask;
  		break;
  
  	case CPUID_MWAIT_LEAF:
  		/* Synthesize the values.. */
  		*ax = 0;
  		*bx = 0;
  		*cx = cpuid_leaf5_ecx_val;
  		*dx = cpuid_leaf5_edx_val;
  		return;
  
  	case CPUID_THERM_POWER_LEAF:
  		/* Disabling APERFMPERF for kernel usage */
  		maskecx = ~(1 << APERFMPERF_PRESENT);
  		break;
  
  	case 0xb:
  		/* Suppress extended topology stuff */
  		maskebx = 0;
  		break;
  	}
  
  	asm(XEN_EMULATE_PREFIX "cpuid"
  		: "=a" (*ax),
  		  "=b" (*bx),
  		  "=c" (*cx),
  		  "=d" (*dx)
  		: "0" (*ax), "2" (*cx));
  
  	*bx &= maskebx;
  	*cx &= maskecx;
  	*cx |= setecx;
  	*dx &= maskedx;
  
  }
  
  static bool __init xen_check_mwait(void)
  {
  #ifdef CONFIG_ACPI
  	struct xen_platform_op op = {
  		.cmd			= XENPF_set_processor_pminfo,
  		.u.set_pminfo.id	= -1,
  		.u.set_pminfo.type	= XEN_PM_PDC,
  	};
  	uint32_t buf[3];
  	unsigned int ax, bx, cx, dx;
  	unsigned int mwait_mask;
  
  	/* We need to determine whether it is OK to expose the MWAIT
  	 * capability to the kernel to harvest deeper than C3 states from ACPI
  	 * _CST using the processor_harvest_xen.c module. For this to work, we
  	 * need to gather the MWAIT_LEAF values (which the cstate.c code
  	 * checks against). The hypervisor won't expose the MWAIT flag because
  	 * it would break backwards compatibility; so we will find out directly
  	 * from the hardware and hypercall.
  	 */
  	if (!xen_initial_domain())
  		return false;
  
  	/*
  	 * When running under platform earlier than Xen4.2, do not expose
  	 * mwait, to avoid the risk of loading native acpi pad driver
  	 */
  	if (!xen_running_on_version_or_later(4, 2))
  		return false;
  
  	ax = 1;
  	cx = 0;
  
  	native_cpuid(&ax, &bx, &cx, &dx);
  
  	mwait_mask = (1 << (X86_FEATURE_EST % 32)) |
  		     (1 << (X86_FEATURE_MWAIT % 32));
  
  	if ((cx & mwait_mask) != mwait_mask)
  		return false;
  
  	/* We need to emulate the MWAIT_LEAF and for that we need both
  	 * ecx and edx. The hypercall provides only partial information.
  	 */
  
  	ax = CPUID_MWAIT_LEAF;
  	bx = 0;
  	cx = 0;
  	dx = 0;
  
  	native_cpuid(&ax, &bx, &cx, &dx);
  
  	/* Ask the Hypervisor whether to clear ACPI_PDC_C_C2C3_FFH. If so,
  	 * don't expose MWAIT_LEAF and let ACPI pick the IOPORT version of C3.
  	 */
  	buf[0] = ACPI_PDC_REVISION_ID;
  	buf[1] = 1;
  	buf[2] = (ACPI_PDC_C_CAPABILITY_SMP | ACPI_PDC_EST_CAPABILITY_SWSMP);
  
  	set_xen_guest_handle(op.u.set_pminfo.pdc, buf);
  
  	if ((HYPERVISOR_dom0_op(&op) == 0) &&
  	    (buf[2] & (ACPI_PDC_C_C1_FFH | ACPI_PDC_C_C2C3_FFH))) {
  		cpuid_leaf5_ecx_val = cx;
  		cpuid_leaf5_edx_val = dx;
  	}
  	return true;
  #else
  	return false;
  #endif
  }
  static void __init xen_init_cpuid_mask(void)
  {
  	unsigned int ax, bx, cx, dx;
  	unsigned int xsave_mask;
  
  	cpuid_leaf1_edx_mask =
  		~((1 << X86_FEATURE_MTRR) |  /* disable MTRR */
  		  (1 << X86_FEATURE_ACC));   /* thermal monitoring */
  
  	if (!xen_initial_domain())
  		cpuid_leaf1_edx_mask &=
  			~((1 << X86_FEATURE_ACPI));  /* disable ACPI */
  
  	cpuid_leaf1_ecx_mask &= ~(1 << (X86_FEATURE_X2APIC % 32));
  
  	ax = 1;
  	cx = 0;
  	cpuid(1, &ax, &bx, &cx, &dx);
  
  	xsave_mask =
  		(1 << (X86_FEATURE_XSAVE % 32)) |
  		(1 << (X86_FEATURE_OSXSAVE % 32));
  
  	/* Xen will set CR4.OSXSAVE if supported and not disabled by force */
  	if ((cx & xsave_mask) != xsave_mask)
  		cpuid_leaf1_ecx_mask &= ~xsave_mask; /* disable XSAVE & OSXSAVE */
  	if (xen_check_mwait())
  		cpuid_leaf1_ecx_set_mask = (1 << (X86_FEATURE_MWAIT % 32));
  }
  
  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 void xen_end_context_switch(struct task_struct *next)
  {
  	xen_mc_flush();
  	paravirt_end_context_switch(next);
  }
  
  static unsigned long xen_store_tr(void)
  {
  	return 0;
  }
  
  /*
   * Set the page permissions for a particular virtual address.  If the
   * address is a vmalloc mapping (or other non-linear mapping), then
   * find the linear mapping of the page and also set its protections to
   * match.
   */
  static void set_aliased_prot(void *v, pgprot_t prot)
  {
  	int level;
  	pte_t *ptep;
  	pte_t pte;
  	unsigned long pfn;
  	struct page *page;
  	unsigned char dummy;
  
  	ptep = lookup_address((unsigned long)v, &level);
  	BUG_ON(ptep == NULL);
  
  	pfn = pte_pfn(*ptep);
  	page = pfn_to_page(pfn);
  
  	pte = pfn_pte(pfn, prot);
  
  	/*
  	 * Careful: update_va_mapping() will fail if the virtual address
  	 * we're poking isn't populated in the page tables.  We don't
  	 * need to worry about the direct map (that's always in the page
  	 * tables), but we need to be careful about vmap space.  In
  	 * particular, the top level page table can lazily propagate
  	 * entries between processes, so if we've switched mms since we
  	 * vmapped the target in the first place, we might not have the
  	 * top-level page table entry populated.
  	 *
  	 * We disable preemption because we want the same mm active when
  	 * we probe the target and when we issue the hypercall.  We'll
  	 * have the same nominal mm, but if we're a kernel thread, lazy
  	 * mm dropping could change our pgd.
  	 *
  	 * Out of an abundance of caution, this uses __get_user() to fault
  	 * in the target address just in case there's some obscure case
  	 * in which the target address isn't readable.
  	 */
  
  	preempt_disable();
  
  	pagefault_disable();	/* Avoid warnings due to being atomic. */
  	__get_user(dummy, (unsigned char __user __force *)v);
  	pagefault_enable();
  
  	if (HYPERVISOR_update_va_mapping((unsigned long)v, pte, 0))
  		BUG();
  
  	if (!PageHighMem(page)) {
  		void *av = __va(PFN_PHYS(pfn));
  
  		if (av != v)
  			if (HYPERVISOR_update_va_mapping((unsigned long)av, pte, 0))
  				BUG();
  	} else
  		kmap_flush_unused();
  
  	preempt_enable();
  }
  
  static void xen_alloc_ldt(struct desc_struct *ldt, unsigned entries)
  {
  	const unsigned entries_per_page = PAGE_SIZE / LDT_ENTRY_SIZE;
  	int i;
  
  	/*
  	 * We need to mark the all aliases of the LDT pages RO.  We
  	 * don't need to call vm_flush_aliases(), though, since that's
  	 * only responsible for flushing aliases out the TLBs, not the
  	 * page tables, and Xen will flush the TLB for us if needed.
  	 *
  	 * To avoid confusing future readers: none of this is necessary
  	 * to load the LDT.  The hypervisor only checks this when the
  	 * LDT is faulted in due to subsequent descriptor access.
  	 */
  
  	for(i = 0; i < entries; i += entries_per_page)
  		set_aliased_prot(ldt + i, PAGE_KERNEL_RO);
  }
  
  static void xen_free_ldt(struct desc_struct *ldt, unsigned entries)
  {
  	const unsigned entries_per_page = PAGE_SIZE / LDT_ENTRY_SIZE;
  	int i;
  
  	for(i = 0; i < entries; i += entries_per_page)
  		set_aliased_prot(ldt + i, PAGE_KERNEL);
  }
  
  static void xen_set_ldt(const void *addr, unsigned entries)
  {
  	struct mmuext_op *op;
  	struct multicall_space mcs = xen_mc_entry(sizeof(*op));
  
  	trace_xen_cpu_set_ldt(addr, entries);
  
  	op = mcs.args;
  	op->cmd = MMUEXT_SET_LDT;
  	op->arg1.linear_addr = (unsigned long)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 desc_ptr *dtr)
  {
  	unsigned long va = dtr->address;
  	unsigned int size = dtr->size + 1;
  	unsigned pages = (size + PAGE_SIZE - 1) / PAGE_SIZE;
  	unsigned long frames[pages];
  	int f;
  
  	/*
  	 * 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);
  
  	for (f = 0; va < dtr->address + size; va += PAGE_SIZE, f++) {
  		int level;
  		pte_t *ptep;
  		unsigned long pfn, mfn;
  		void *virt;
  
  		/*
  		 * The GDT is per-cpu and is in the percpu data area.
  		 * That can be virtually mapped, so we need to do a
  		 * page-walk to get the underlying MFN for the
  		 * hypercall.  The page can also be in the kernel's
  		 * linear range, so we need to RO that mapping too.
  		 */
  		ptep = lookup_address(va, &level);
  		BUG_ON(ptep == NULL);
  
  		pfn = pte_pfn(*ptep);
  		mfn = pfn_to_mfn(pfn);
  		virt = __va(PFN_PHYS(pfn));
  
  		frames[f] = mfn;
  
  		make_lowmem_page_readonly((void *)va);
  		make_lowmem_page_readonly(virt);
  	}
  
  	if (HYPERVISOR_set_gdt(frames, size / sizeof(struct desc_struct)))
  		BUG();
  }
  
  /*
   * load_gdt for early boot, when the gdt is only mapped once
   */
  static void __init xen_load_gdt_boot(const struct desc_ptr *dtr)
  {
  	unsigned long va = dtr->address;
  	unsigned int size = dtr->size + 1;
  	unsigned pages = (size + PAGE_SIZE - 1) / PAGE_SIZE;
  	unsigned long frames[pages];
  	int f;
  
  	/*
  	 * 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);
  
  	for (f = 0; va < dtr->address + size; va += PAGE_SIZE, f++) {
  		pte_t pte;
  		unsigned long pfn, mfn;
  
  		pfn = virt_to_pfn(va);
  		mfn = pfn_to_mfn(pfn);
  
  		pte = pfn_pte(pfn, PAGE_KERNEL_RO);
  
  		if (HYPERVISOR_update_va_mapping((unsigned long)va, pte, 0))
  			BUG();
  
  		frames[f] = mfn;
  	}
  
  	if (HYPERVISOR_set_gdt(frames, size / sizeof(struct desc_struct)))
  		BUG();
  }
  
  static inline bool desc_equal(const struct desc_struct *d1,
  			      const struct desc_struct *d2)
  {
  	return d1->a == d2->a && d1->b == d2->b;
  }
  
  static void load_TLS_descriptor(struct thread_struct *t,
  				unsigned int cpu, unsigned int i)
  {
  	struct desc_struct *shadow = &per_cpu(shadow_tls_desc, cpu).desc[i];
  	struct desc_struct *gdt;
  	xmaddr_t maddr;
  	struct multicall_space mc;
  
  	if (desc_equal(shadow, &t->tls_array[i]))
  		return;
  
  	*shadow = t->tls_array[i];
  
  	gdt = get_cpu_gdt_table(cpu);
  	maddr = arbitrary_virt_to_machine(&gdt[GDT_ENTRY_TLS_MIN+i]);
  	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)
  {
  	/*
  	 * XXX sleazy hack: If we're being called in a lazy-cpu zone
  	 * and lazy gs handling is enabled, 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.
  	 *
  	 * On x86_64, this hack is not used for %gs, because gs points
  	 * to KERNEL_GS_BASE (and uses it for PDA references), so we
  	 * must not zero %gs on x86_64
  	 *
  	 * For x86_64, we need to zero %fs, otherwise we may get an
  	 * exception between the new %fs descriptor being loaded and
  	 * %fs being effectively cleared at __switch_to().
  	 */
  	if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_CPU) {
  #ifdef CONFIG_X86_32
  		lazy_load_gs(0);
  #else
  		loadsegment(fs, 0);
  #endif
  	}
  
  	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);
  }
  
  #ifdef CONFIG_X86_64
  static void xen_load_gs_index(unsigned int idx)
  {
  	if (HYPERVISOR_set_segment_base(SEGBASE_GS_USER_SEL, idx))
  		BUG();
  }
  #endif
  
  static void xen_write_ldt_entry(struct desc_struct *dt, int entrynum,
  				const void *ptr)
  {
  	xmaddr_t mach_lp = arbitrary_virt_to_machine(&dt[entrynum]);
  	u64 entry = *(u64 *)ptr;
  
  	trace_xen_cpu_write_ldt_entry(dt, entrynum, entry);
  
  	preempt_disable();
  
  	xen_mc_flush();
  	if (HYPERVISOR_update_descriptor(mach_lp.maddr, entry))
  		BUG();
  
  	preempt_enable();
  }
  
  static int cvt_gate_to_trap(int vector, const gate_desc *val,
  			    struct trap_info *info)
  {
  	unsigned long addr;
  
  	if (val->type != GATE_TRAP && val->type != GATE_INTERRUPT)
  		return 0;
  
  	info->vector = vector;
  
  	addr = gate_offset(*val);
  #ifdef CONFIG_X86_64
  	/*
  	 * Look for known traps using IST, and substitute them
  	 * appropriately.  The debugger ones are the only ones we care
  	 * about.  Xen will handle faults like double_fault,
  	 * so we should never see them.  Warn if
  	 * there's an unexpected IST-using fault handler.
  	 */
  	if (addr == (unsigned long)debug)
  		addr = (unsigned long)xen_debug;
  	else if (addr == (unsigned long)int3)
  		addr = (unsigned long)xen_int3;
  	else if (addr == (unsigned long)stack_segment)
  		addr = (unsigned long)xen_stack_segment;
  	else if (addr == (unsigned long)double_fault) {
  		/* Don't need to handle these */
  		return 0;
  #ifdef CONFIG_X86_MCE
  	} else if (addr == (unsigned long)machine_check) {
  		/*
  		 * when xen hypervisor inject vMCE to guest,
  		 * use native mce handler to handle it
  		 */
  		;
  #endif
  	} else if (addr == (unsigned long)nmi)
  		/*
  		 * Use the native version as well.
  		 */
  		;
  	else {
  		/* Some other trap using IST? */
  		if (WARN_ON(val->ist != 0))
  			return 0;
  	}
  #endif	/* CONFIG_X86_64 */
  	info->address = addr;
  
  	info->cs = gate_segment(*val);
  	info->flags = val->dpl;
  	/* interrupt gates clear IF */
  	if (val->type == GATE_INTERRUPT)
  		info->flags |= 1 << 2;
  
  	return 1;
  }
  
  /* Locations of each CPU's IDT */
  static DEFINE_PER_CPU(struct desc_ptr, 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(gate_desc *dt, int entrynum, const gate_desc *g)
  {
  	unsigned long p = (unsigned long)&dt[entrynum];
  	unsigned long start, end;
  
  	trace_xen_cpu_write_idt_entry(dt, entrynum, g);
  
  	preempt_disable();
  
  	start = __this_cpu_read(idt_desc.address);
  	end = start + __this_cpu_read(idt_desc.size) + 1;
  
  	xen_mc_flush();
  
  	native_write_idt_entry(dt, entrynum, g);
  
  	if (p >= start && (p + 8) <= end) {
  		struct trap_info info[2];
  
  		info[1].address = 0;
  
  		if (cvt_gate_to_trap(entrynum, g, &info[0]))
  			if (HYPERVISOR_set_trap_table(info))
  				BUG();
  	}
  
  	preempt_enable();
  }
  
  static void xen_convert_trap_info(const struct desc_ptr *desc,
  				  struct trap_info *traps)
  {
  	unsigned in, out, count;
  
  	count = (desc->size+1) / sizeof(gate_desc);
  	BUG_ON(count > 256);
  
  	for (in = out = 0; in < count; in++) {
  		gate_desc *entry = (gate_desc*)(desc->address) + in;
  
  		if (cvt_gate_to_trap(in, entry, &traps[out]))
  			out++;
  	}
  	traps[out].address = 0;
  }
  
  void xen_copy_trap_info(struct trap_info *traps)
  {
  	const struct desc_ptr *desc = this_cpu_ptr(&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 desc_ptr *desc)
  {
  	static DEFINE_SPINLOCK(lock);
  	static struct trap_info traps[257];
  
  	trace_xen_cpu_load_idt(desc);
  
  	spin_lock(&lock);
  
  	memcpy(this_cpu_ptr(&idt_desc), desc, sizeof(idt_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,
  				const void *desc, int type)
  {
  	trace_xen_cpu_write_gdt_entry(dt, entry, desc, type);
  
  	preempt_disable();
  
  	switch (type) {
  	case DESC_LDT:
  	case DESC_TSS:
  		/* ignore */
  		break;
  
  	default: {
  		xmaddr_t maddr = arbitrary_virt_to_machine(&dt[entry]);
  
  		xen_mc_flush();
  		if (HYPERVISOR_update_descriptor(maddr.maddr, *(u64 *)desc))
  			BUG();
  	}
  
  	}
  
  	preempt_enable();
  }
  
  /*
   * Version of write_gdt_entry for use at early boot-time needed to
   * update an entry as simply as possible.
   */
  static void __init xen_write_gdt_entry_boot(struct desc_struct *dt, int entry,
  					    const void *desc, int type)
  {
  	trace_xen_cpu_write_gdt_entry(dt, entry, desc, type);
  
  	switch (type) {
  	case DESC_LDT:
  	case DESC_TSS:
  		/* ignore */
  		break;
  
  	default: {
  		xmaddr_t maddr = virt_to_machine(&dt[entry]);
  
  		if (HYPERVISOR_update_descriptor(maddr.maddr, *(u64 *)desc))
  			dt[entry] = *(struct desc_struct *)desc;
  	}
  
  	}
  }
  
  static void xen_load_sp0(struct tss_struct *tss,
  			 struct thread_struct *thread)
  {
  	struct multicall_space mcs;
  
  	mcs = xen_mc_entry(0);
  	MULTI_stack_switch(mcs.mc, __KERNEL_DS, thread->sp0);
  	xen_mc_issue(PARAVIRT_LAZY_CPU);
  	tss->x86_tss.sp0 = thread->sp0;
  }
  
  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)
  {
  }
  
  static void xen_clts(void)
  {
  	struct multicall_space mcs;
  
  	mcs = xen_mc_entry(0);
  
  	MULTI_fpu_taskswitch(mcs.mc, 0);
  
  	xen_mc_issue(PARAVIRT_LAZY_CPU);
  }
  
  static DEFINE_PER_CPU(unsigned long, xen_cr0_value);
  
  static unsigned long xen_read_cr0(void)
  {
  	unsigned long cr0 = this_cpu_read(xen_cr0_value);
  
  	if (unlikely(cr0 == 0)) {
  		cr0 = native_read_cr0();
  		this_cpu_write(xen_cr0_value, cr0);
  	}
  
  	return cr0;
  }
  
  static void xen_write_cr0(unsigned long cr0)
  {
  	struct multicall_space mcs;
  
  	this_cpu_write(xen_cr0_value, cr0);
  
  	/* Only pay attention to cr0.TS; everything else is
  	   ignored. */
  	mcs = xen_mc_entry(0);
  
  	MULTI_fpu_taskswitch(mcs.mc, (cr0 & X86_CR0_TS) != 0);
  
  	xen_mc_issue(PARAVIRT_LAZY_CPU);
  }
  
  static void xen_write_cr4(unsigned long cr4)
  {
  	cr4 &= ~(X86_CR4_PGE | X86_CR4_PSE | X86_CR4_PCE);
  
  	native_write_cr4(cr4);
  }
  #ifdef CONFIG_X86_64
  static inline unsigned long xen_read_cr8(void)
  {
  	return 0;
  }
  static inline void xen_write_cr8(unsigned long val)
  {
  	BUG_ON(val);
  }
  #endif
  
  static u64 xen_read_msr_safe(unsigned int msr, int *err)
  {
  	u64 val;
  
  	if (pmu_msr_read(msr, &val, err))
  		return val;
  
  	val = native_read_msr_safe(msr, err);
  	switch (msr) {
  	case MSR_IA32_APICBASE:
  #ifdef CONFIG_X86_X2APIC
  		if (!(cpuid_ecx(1) & (1 << (X86_FEATURE_X2APIC & 31))))
  #endif
  			val &= ~X2APIC_ENABLE;
  		break;
  	}
  	return val;
  }
  
  static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
  {
  	int ret;
  
  	ret = 0;
  
  	switch (msr) {
  #ifdef CONFIG_X86_64
  		unsigned which;
  		u64 base;
  
  	case MSR_FS_BASE:		which = SEGBASE_FS; goto set;
  	case MSR_KERNEL_GS_BASE:	which = SEGBASE_GS_USER; goto set;
  	case MSR_GS_BASE:		which = SEGBASE_GS_KERNEL; goto set;
  
  	set:
  		base = ((u64)high << 32) | low;
  		if (HYPERVISOR_set_segment_base(which, base) != 0)
  			ret = -EIO;
  		break;
  #endif
  
  	case MSR_STAR:
  	case MSR_CSTAR:
  	case MSR_LSTAR:
  	case MSR_SYSCALL_MASK:
  	case MSR_IA32_SYSENTER_CS:
  	case MSR_IA32_SYSENTER_ESP:
  	case MSR_IA32_SYSENTER_EIP:
  		/* Fast syscall setup is all done in hypercalls, so
  		   these are all ignored.  Stub them out here to stop
  		   Xen console noise. */
  		break;
  
  	default:
  		if (!pmu_msr_write(msr, low, high, &ret))
  			ret = native_write_msr_safe(msr, low, high);
  	}
  
  	return ret;
  }
  
  void xen_setup_shared_info(void)
  {
  	if (!xen_feature(XENFEAT_auto_translated_physmap)) {
  		set_fixmap(FIX_PARAVIRT_BOOTMAP,
  			   xen_start_info->shared_info);
  
  		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);
  
  #ifndef CONFIG_SMP
  	/* In UP this is as good a place as any to set up shared info */
  	xen_setup_vcpu_info_placement();
  #endif
  
  	xen_setup_mfn_list_list();
  }
  
  /* This is called once we have the cpu_possible_mask */
  void 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. Note that for
  	 * PVH we want to use native IRQ mechanism. */
  	if (have_vcpu_info_placement && !xen_pvh_domain()) {
  		pv_irq_ops.save_fl = __PV_IS_CALLEE_SAVE(xen_save_fl_direct);
  		pv_irq_ops.restore_fl = __PV_IS_CALLEE_SAVE(xen_restore_fl_direct);
  		pv_irq_ops.irq_disable = __PV_IS_CALLEE_SAVE(xen_irq_disable_direct);
  		pv_irq_ops.irq_enable = __PV_IS_CALLEE_SAVE(xen_irq_enable_direct);
  		pv_mmu_ops.read_cr2 = xen_read_cr2_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 __initconst = {
  	.paravirt_enabled = 1,
  	.shared_kernel_pmd = 0,
  
  #ifdef CONFIG_X86_64
  	.extra_user_64bit_cs = FLAT_USER_CS64,
  #endif
  	.features = 0,
  	.name = "Xen",
  };
  
  static const struct pv_init_ops xen_init_ops __initconst = {
  	.patch = xen_patch,
  };
  
  static const struct pv_cpu_ops xen_cpu_ops __initconst = {
  	.cpuid = xen_cpuid,
  
  	.set_debugreg = xen_set_debugreg,
  	.get_debugreg = xen_get_debugreg,
  
  	.clts = xen_clts,
  
  	.read_cr0 = xen_read_cr0,
  	.write_cr0 = xen_write_cr0,
  
  	.read_cr4 = native_read_cr4,
  	.read_cr4_safe = native_read_cr4_safe,
  	.write_cr4 = xen_write_cr4,
  
  #ifdef CONFIG_X86_64
  	.read_cr8 = xen_read_cr8,
  	.write_cr8 = xen_write_cr8,
  #endif
  
  	.wbinvd = native_wbinvd,
  
  	.read_msr = xen_read_msr_safe,
  	.write_msr = xen_write_msr_safe,
  
  	.read_pmc = xen_read_pmc,
  
  	.iret = xen_iret,
  #ifdef CONFIG_X86_64
  	.usergs_sysret32 = xen_sysret32,
  	.usergs_sysret64 = xen_sysret64,
  #else
  	.irq_enable_sysexit = xen_sysexit,
  #endif
  
  	.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,
  #ifdef CONFIG_X86_64
  	.load_gs_index = xen_load_gs_index,
  #endif
  
  	.alloc_ldt = xen_alloc_ldt,
  	.free_ldt = xen_free_ldt,
  
  	.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_sp0 = xen_load_sp0,
  
  	.set_iopl_mask = xen_set_iopl_mask,
  	.io_delay = xen_io_delay,
  
  	/* Xen takes care of %gs when switching to usermode for us */
  	.swapgs = paravirt_nop,
  
  	.start_context_switch = paravirt_start_context_switch,
  	.end_context_switch = xen_end_context_switch,
  };
  
  static const struct pv_apic_ops xen_apic_ops __initconst = {
  #ifdef CONFIG_X86_LOCAL_APIC
  	.startup_ipi_hook = paravirt_nop,
  #endif
  };
  
  static 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 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_machine_power_off(void)
  {
  	if (pm_power_off)
  		pm_power_off();
  	xen_reboot(SHUTDOWN_poweroff);
  }
  
  static void xen_crash_shutdown(struct pt_regs *regs)
  {
  	xen_reboot(SHUTDOWN_crash);
  }
  
  static int
  xen_panic_event(struct notifier_block *this, unsigned long event, void *ptr)
  {
  	xen_reboot(SHUTDOWN_crash);
  	return NOTIFY_DONE;
  }
  
  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;
  }
  
  static const struct machine_ops xen_machine_ops __initconst = {
  	.restart = xen_restart,
  	.halt = xen_machine_halt,
  	.power_off = xen_machine_power_off,
  	.shutdown = xen_machine_halt,
  	.crash_shutdown = xen_crash_shutdown,
  	.emergency_restart = xen_emergency_restart,
  };
  
  static unsigned char xen_get_nmi_reason(void)
  {
  	unsigned char reason = 0;
  
  	/* Construct a value which looks like it came from port 0x61. */
  	if (test_bit(_XEN_NMIREASON_io_error,
  		     &HYPERVISOR_shared_info->arch.nmi_reason))
  		reason |= NMI_REASON_IOCHK;
  	if (test_bit(_XEN_NMIREASON_pci_serr,
  		     &HYPERVISOR_shared_info->arch.nmi_reason))
  		reason |= NMI_REASON_SERR;
  
  	return reason;
  }
  
  static void __init xen_boot_params_init_edd(void)
  {
  #if IS_ENABLED(CONFIG_EDD)
  	struct xen_platform_op op;
  	struct edd_info *edd_info;
  	u32 *mbr_signature;
  	unsigned nr;
  	int ret;
  
  	edd_info = boot_params.eddbuf;
  	mbr_signature = boot_params.edd_mbr_sig_buffer;
  
  	op.cmd = XENPF_firmware_info;
  
  	op.u.firmware_info.type = XEN_FW_DISK_INFO;
  	for (nr = 0; nr < EDDMAXNR; nr++) {
  		struct edd_info *info = edd_info + nr;
  
  		op.u.firmware_info.index = nr;
  		info->params.length = sizeof(info->params);
  		set_xen_guest_handle(op.u.firmware_info.u.disk_info.edd_params,
  				     &info->params);
  		ret = HYPERVISOR_dom0_op(&op);
  		if (ret)
  			break;
  
  #define C(x) info->x = op.u.firmware_info.u.disk_info.x
  		C(device);
  		C(version);
  		C(interface_support);
  		C(legacy_max_cylinder);
  		C(legacy_max_head);
  		C(legacy_sectors_per_track);
  #undef C
  	}
  	boot_params.eddbuf_entries = nr;
  
  	op.u.firmware_info.type = XEN_FW_DISK_MBR_SIGNATURE;
  	for (nr = 0; nr < EDD_MBR_SIG_MAX; nr++) {
  		op.u.firmware_info.index = nr;
  		ret = HYPERVISOR_dom0_op(&op);
  		if (ret)
  			break;
  		mbr_signature[nr] = op.u.firmware_info.u.disk_mbr_signature.mbr_signature;
  	}
  	boot_params.edd_mbr_sig_buf_entries = nr;
  #endif
  }
  
  /*
   * Set up the GDT and segment registers for -fstack-protector.  Until
   * we do this, we have to be careful not to call any stack-protected
   * function, which is most of the kernel.
   *
   * Note, that it is __ref because the only caller of this after init
   * is PVH which is not going to use xen_load_gdt_boot or other
   * __init functions.
   */
  static void __ref xen_setup_gdt(int cpu)
  {
  	if (xen_feature(XENFEAT_auto_translated_physmap)) {
  #ifdef CONFIG_X86_64
  		unsigned long dummy;
  
  		load_percpu_segment(cpu); /* We need to access per-cpu area */
  		switch_to_new_gdt(cpu); /* GDT and GS set */
  
  		/* We are switching of the Xen provided GDT to our HVM mode
  		 * GDT. The new GDT has  __KERNEL_CS with CS.L = 1
  		 * and we are jumping to reload it.
  		 */
  		asm volatile ("pushq %0\n"
  			      "leaq 1f(%%rip),%0\n"
  			      "pushq %0\n"
  			      "lretq\n"
  			      "1:\n"
  			      : "=&r" (dummy) : "0" (__KERNEL_CS));
  
  		/*
  		 * While not needed, we also set the %es, %ds, and %fs
  		 * to zero. We don't care about %ss as it is NULL.
  		 * Strictly speaking this is not needed as Xen zeros those
  		 * out (and also MSR_FS_BASE, MSR_GS_BASE, MSR_KERNEL_GS_BASE)
  		 *
  		 * Linux zeros them in cpu_init() and in secondary_startup_64
  		 * (for BSP).
  		 */
  		loadsegment(es, 0);
  		loadsegment(ds, 0);
  		loadsegment(fs, 0);
  #else
  		/* PVH: TODO Implement. */
  		BUG();
  #endif
  		return; /* PVH does not need any PV GDT ops. */
  	}
  	pv_cpu_ops.write_gdt_entry = xen_write_gdt_entry_boot;
  	pv_cpu_ops.load_gdt = xen_load_gdt_boot;
  
  	setup_stack_canary_segment(0);
  	switch_to_new_gdt(0);
  
  	pv_cpu_ops.write_gdt_entry = xen_write_gdt_entry;
  	pv_cpu_ops.load_gdt = xen_load_gdt;
  }
  
  #ifdef CONFIG_XEN_PVH
  /*
   * A PV guest starts with default flags that are not set for PVH, set them
   * here asap.
   */
  static void xen_pvh_set_cr_flags(int cpu)
  {
  
  	/* Some of these are setup in 'secondary_startup_64'. The others:
  	 * X86_CR0_TS, X86_CR0_PE, X86_CR0_ET are set by Xen for HVM guests
  	 * (which PVH shared codepaths), while X86_CR0_PG is for PVH. */
  	write_cr0(read_cr0() | X86_CR0_MP | X86_CR0_NE | X86_CR0_WP | X86_CR0_AM);
  
  	if (!cpu)
  		return;
  	/*
  	 * For BSP, PSE PGE are set in probe_page_size_mask(), for APs
  	 * set them here. For all, OSFXSR OSXMMEXCPT are set in fpu__init_cpu().
  	*/
  	if (cpu_has_pse)
  		cr4_set_bits_and_update_boot(X86_CR4_PSE);
  
  	if (cpu_has_pge)
  		cr4_set_bits_and_update_boot(X86_CR4_PGE);
  }
  
  /*
   * Note, that it is ref - because the only caller of this after init
   * is PVH which is not going to use xen_load_gdt_boot or other
   * __init functions.
   */
  void __ref xen_pvh_secondary_vcpu_init(int cpu)
  {
  	xen_setup_gdt(cpu);
  	xen_pvh_set_cr_flags(cpu);
  }
  
  static void __init xen_pvh_early_guest_init(void)
  {
  	if (!xen_feature(XENFEAT_auto_translated_physmap))
  		return;
  
  	if (!xen_feature(XENFEAT_hvm_callback_vector))
  		return;
  
  	xen_have_vector_callback = 1;
  
  	xen_pvh_early_cpu_init(0, false);
  	xen_pvh_set_cr_flags(0);
  
  #ifdef CONFIG_X86_32
  	BUG(); /* PVH: Implement proper support. */
  #endif
  }
  #endif    /* CONFIG_XEN_PVH */
  
  /* First C function to be called on Xen boot */
  asmlinkage __visible void __init xen_start_kernel(void)
  {
  	struct physdev_set_iopl set_iopl;
  	unsigned long initrd_start = 0;
  	u64 pat;
  	int rc;
  
  	if (!xen_start_info)
  		return;
  
  	xen_domain_type = XEN_PV_DOMAIN;
  
  	xen_setup_features();
  #ifdef CONFIG_XEN_PVH
  	xen_pvh_early_guest_init();
  #endif
  	xen_setup_machphys_mapping();
  
  	/* Install Xen paravirt ops */
  	pv_info = xen_info;
  	if (xen_initial_domain())
  		pv_info.features |= PV_SUPPORTED_RTC;
  	pv_init_ops = xen_init_ops;
  	pv_apic_ops = xen_apic_ops;
  	if (!xen_pvh_domain()) {
  		pv_cpu_ops = xen_cpu_ops;
  
  		x86_platform.get_nmi_reason = xen_get_nmi_reason;
  	}
  
  	if (xen_feature(XENFEAT_auto_translated_physmap))
  		x86_init.resources.memory_setup = xen_auto_xlated_memory_setup;
  	else
  		x86_init.resources.memory_setup = xen_memory_setup;
  	x86_init.oem.arch_setup = xen_arch_setup;
  	x86_init.oem.banner = xen_banner;
  
  	xen_init_time_ops();
  
  	/*
  	 * Set up some pagetable state before starting to set any ptes.
  	 */
  
  	xen_init_mmu_ops();
  
  	/* Prevent unwanted bits from being set in PTEs. */
  	__supported_pte_mask &= ~_PAGE_GLOBAL;
  
  	/*
  	 * Prevent page tables from being allocated in highmem, even
  	 * if CONFIG_HIGHPTE is enabled.
  	 */
  	__userpte_alloc_gfp &= ~__GFP_HIGHMEM;
  
  	/* Work out if we support NX */
  	x86_configure_nx();
  
  	/* Get mfn list */
  	xen_build_dynamic_phys_to_machine();
  
  	/*
  	 * Set up kernel GDT and segment registers, mainly so that
  	 * -fstack-protector code can be executed.
  	 */
  	xen_setup_gdt(0);
  
  	xen_init_irq_ops();
  	xen_init_cpuid_mask();
  
  #ifdef CONFIG_X86_LOCAL_APIC
  	/*
  	 * set up the basic apic ops.
  	 */
  	xen_init_apic();
  #endif
  
  	if (xen_feature(XENFEAT_mmu_pt_update_preserve_ad)) {
  		pv_mmu_ops.ptep_modify_prot_start = xen_ptep_modify_prot_start;
  		pv_mmu_ops.ptep_modify_prot_commit = xen_ptep_modify_prot_commit;
  	}
  
  	machine_ops = xen_machine_ops;
  
  	/*
  	 * The only reliable way to retain the initial address of the
  	 * percpu gdt_page is to remember it here, so we can go and
  	 * mark it RW later, when the initial percpu area is freed.
  	 */
  	xen_initial_gdt = &per_cpu(gdt_page, 0);
  
  	xen_smp_init();
  
  #ifdef CONFIG_ACPI_NUMA
  	/*
  	 * The pages we from Xen are not related to machine pages, so
  	 * any NUMA information the kernel tries to get from ACPI will
  	 * be meaningless.  Prevent it from trying.
  	 */
  	acpi_numa = -1;
  #endif
  	/* Don't do the full vcpu_info placement stuff until we have a
  	   possible map and a non-dummy shared_info. */
  	per_cpu(xen_vcpu, 0) = &HYPERVISOR_shared_info->vcpu_info[0];
  
  	local_irq_disable();
  	early_boot_irqs_disabled = true;
  
  	xen_raw_console_write("mapping kernel into physical memory\n");
  	xen_setup_kernel_pagetable((pgd_t *)xen_start_info->pt_base,
  				   xen_start_info->nr_pages);
  	xen_reserve_special_pages();
  
  	/*
  	 * Modify the cache mode translation tables to match Xen's PAT
  	 * configuration.
  	 */
  	rdmsrl(MSR_IA32_CR_PAT, pat);
  	pat_init_cache_modes(pat);
  
  	/* keep using Xen gdt for now; no urgent need to change it */
  
  #ifdef CONFIG_X86_32
  	pv_info.kernel_rpl = 1;
  	if (xen_feature(XENFEAT_supervisor_mode_kernel))
  		pv_info.kernel_rpl = 0;
  #else
  	pv_info.kernel_rpl = 0;
  #endif
  	/* set the limit of our address space */
  	xen_reserve_top();
  
  	/* PVH: runs at default kernel iopl of 0 */
  	if (!xen_pvh_domain()) {
  		/*
  		 * We used to do this in xen_arch_setup, but that is too late
  		 * on AMD were early_cpu_init (run before ->arch_setup()) calls
  		 * early_amd_init which pokes 0xcf8 port.
  		 */
  		set_iopl.iopl = 1;
  		rc = HYPERVISOR_physdev_op(PHYSDEVOP_set_iopl, &set_iopl);
  		if (rc != 0)
  			xen_raw_printk("physdev_op failed %d\n", rc);
  	}
  
  #ifdef CONFIG_X86_32
  	/* set up basic CPUID stuff */
  	cpu_detect(&new_cpu_data);
  	set_cpu_cap(&new_cpu_data, X86_FEATURE_FPU);
  	new_cpu_data.wp_works_ok = 1;
  	new_cpu_data.x86_capability[0] = cpuid_edx(1);
  #endif
  
  	if (xen_start_info->mod_start) {
  	    if (xen_start_info->flags & SIF_MOD_START_PFN)
  		initrd_start = PFN_PHYS(xen_start_info->mod_start);
  	    else
  		initrd_start = __pa(xen_start_info->mod_start);
  	}
  
  	/* Poke various useful things into boot_params */
  	boot_params.hdr.type_of_loader = (9 << 4) | 0;
  	boot_params.hdr.ramdisk_image = initrd_start;
  	boot_params.hdr.ramdisk_size = xen_start_info->mod_len;
  	boot_params.hdr.cmd_line_ptr = __pa(xen_start_info->cmd_line);
  
  	if (!xen_initial_domain()) {
  		add_preferred_console("xenboot", 0, NULL);
  		add_preferred_console("tty", 0, NULL);
  		add_preferred_console("hvc", 0, NULL);
  		if (pci_xen)
  			x86_init.pci.arch_init = pci_xen_init;
  	} else {
  		const struct dom0_vga_console_info *info =
  			(void *)((char *)xen_start_info +
  				 xen_start_info->console.dom0.info_off);
  		struct xen_platform_op op = {
  			.cmd = XENPF_firmware_info,
  			.interface_version = XENPF_INTERFACE_VERSION,
  			.u.firmware_info.type = XEN_FW_KBD_SHIFT_FLAGS,
  		};
  
  		xen_init_vga(info, xen_start_info->console.dom0.info_size);
  		xen_start_info->console.domU.mfn = 0;
  		xen_start_info->console.domU.evtchn = 0;
  
  		if (HYPERVISOR_dom0_op(&op) == 0)
  			boot_params.kbd_status = op.u.firmware_info.u.kbd_shift_flags;
  
  		/* Make sure ACS will be enabled */
  		pci_request_acs();
  
  		xen_acpi_sleep_register();
  
  		/* Avoid searching for BIOS MP tables */
  		x86_init.mpparse.find_smp_config = x86_init_noop;
  		x86_init.mpparse.get_smp_config = x86_init_uint_noop;
  
  		xen_boot_params_init_edd();
  	}
  #ifdef CONFIG_PCI
  	/* PCI BIOS service won't work from a PV guest. */
  	pci_probe &= ~PCI_PROBE_BIOS;
  #endif
  	xen_raw_console_write("about to get started...\n");
  
  	xen_setup_runstate_info(0);
  
  	xen_efi_init();
  
  	/* Start the world */
  #ifdef CONFIG_X86_32
  	i386_start_kernel();
  #else
  	cr4_init_shadow(); /* 32b kernel does this in i386_start_kernel() */
  	x86_64_start_reservations((char *)__pa_symbol(&boot_params));
  #endif
  }
  
  void __ref xen_hvm_init_shared_info(void)
  {
  	int cpu;
  	struct xen_add_to_physmap xatp;
  	static struct shared_info *shared_info_page = 0;
  
  	if (!shared_info_page)
  		shared_info_page = (struct shared_info *)
  			extend_brk(PAGE_SIZE, PAGE_SIZE);
  	xatp.domid = DOMID_SELF;
  	xatp.idx = 0;
  	xatp.space = XENMAPSPACE_shared_info;
  	xatp.gpfn = __pa(shared_info_page) >> PAGE_SHIFT;
  	if (HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp))
  		BUG();
  
  	HYPERVISOR_shared_info = (struct shared_info *)shared_info_page;
  
  	/* xen_vcpu is a pointer to the vcpu_info struct in the shared_info
  	 * page, we use it in the event channel upcall and in some pvclock
  	 * related functions. We don't need the vcpu_info placement
  	 * optimizations because we don't use any pv_mmu or pv_irq op on
  	 * HVM.
  	 * When xen_hvm_init_shared_info is run at boot time only vcpu 0 is
  	 * online but xen_hvm_init_shared_info is run at resume time too and
  	 * in that case multiple vcpus might be online. */
  	for_each_online_cpu(cpu) {
  		/* Leave it to be NULL. */
  		if (cpu >= MAX_VIRT_CPUS)
  			continue;
  		per_cpu(xen_vcpu, cpu) = &HYPERVISOR_shared_info->vcpu_info[cpu];
  	}
  }
  
  #ifdef CONFIG_XEN_PVHVM
  static void __init init_hvm_pv_info(void)
  {
  	int major, minor;
  	uint32_t eax, ebx, ecx, edx, pages, msr, base;
  	u64 pfn;
  
  	base = xen_cpuid_base();
  	cpuid(base + 1, &eax, &ebx, &ecx, &edx);
  
  	major = eax >> 16;
  	minor = eax & 0xffff;
  	printk(KERN_INFO "Xen version %d.%d.\n", major, minor);
  
  	cpuid(base + 2, &pages, &msr, &ecx, &edx);
  
  	pfn = __pa(hypercall_page);
  	wrmsr_safe(msr, (u32)pfn, (u32)(pfn >> 32));
  
  	xen_setup_features();
  
  	pv_info.name = "Xen HVM";
  
  	xen_domain_type = XEN_HVM_DOMAIN;
  }
  
  static int xen_hvm_cpu_notify(struct notifier_block *self, unsigned long action,
  			      void *hcpu)
  {
  	int cpu = (long)hcpu;
  	switch (action) {
  	case CPU_UP_PREPARE:
  		xen_vcpu_setup(cpu);
  		if (xen_have_vector_callback) {
  			if (xen_feature(XENFEAT_hvm_safe_pvclock))
  				xen_setup_timer(cpu);
  		}
  		break;
  	default:
  		break;
  	}
  	return NOTIFY_OK;
  }
  
  static struct notifier_block xen_hvm_cpu_notifier = {
  	.notifier_call	= xen_hvm_cpu_notify,
  };
  
  #ifdef CONFIG_KEXEC_CORE
  static void xen_hvm_shutdown(void)
  {
  	native_machine_shutdown();
  	if (kexec_in_progress)
  		xen_reboot(SHUTDOWN_soft_reset);
  }
  
  static void xen_hvm_crash_shutdown(struct pt_regs *regs)
  {
  	native_machine_crash_shutdown(regs);
  	xen_reboot(SHUTDOWN_soft_reset);
  }
  #endif
  
  static void __init xen_hvm_guest_init(void)
  {
  	if (xen_pv_domain())
  		return;
  
  	init_hvm_pv_info();
  
  	xen_hvm_init_shared_info();
  
  	xen_panic_handler_init();
  
  	if (xen_feature(XENFEAT_hvm_callback_vector))
  		xen_have_vector_callback = 1;
  	xen_hvm_smp_init();
  	register_cpu_notifier(&xen_hvm_cpu_notifier);
  	xen_unplug_emulated_devices();
  	x86_init.irqs.intr_init = xen_init_IRQ;
  	xen_hvm_init_time_ops();
  	xen_hvm_init_mmu_ops();
  #ifdef CONFIG_KEXEC_CORE
  	machine_ops.shutdown = xen_hvm_shutdown;
  	machine_ops.crash_shutdown = xen_hvm_crash_shutdown;
  #endif
  }
  #endif
  
  static bool xen_nopv = false;
  static __init int xen_parse_nopv(char *arg)
  {
         xen_nopv = true;
         return 0;
  }
  early_param("xen_nopv", xen_parse_nopv);
  
  static uint32_t __init xen_platform(void)
  {
  	if (xen_nopv)
  		return 0;
  
  	return xen_cpuid_base();
  }
  
  bool xen_hvm_need_lapic(void)
  {
  	if (xen_nopv)
  		return false;
  	if (xen_pv_domain())
  		return false;
  	if (!xen_hvm_domain())
  		return false;
  	if (xen_feature(XENFEAT_hvm_pirqs) && xen_have_vector_callback)
  		return false;
  	return true;
  }
  EXPORT_SYMBOL_GPL(xen_hvm_need_lapic);
  
  static void xen_set_cpu_features(struct cpuinfo_x86 *c)
  {
  	if (xen_pv_domain()) {
  		clear_cpu_bug(c, X86_BUG_SYSRET_SS_ATTRS);
  		set_cpu_cap(c, X86_FEATURE_XENPV);
  	}
  }
  
  const struct hypervisor_x86 x86_hyper_xen = {
  	.name			= "Xen",
  	.detect			= xen_platform,
  #ifdef CONFIG_XEN_PVHVM
  	.init_platform		= xen_hvm_guest_init,
  #endif
  	.x2apic_available	= xen_x2apic_para_available,
  	.set_cpu_features       = xen_set_cpu_features,
  };
  EXPORT_SYMBOL(x86_hyper_xen);
  
  #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
  