FreeBSD/Linux Kernel Cross Reference
sys/i386/xen/xen_machdep.c

     /*
      *
      * Copyright (c) 2004 Christian Limpach.
      * Copyright (c) 2004-2006,2008 Kip Macy
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *      This product includes software developed by Christian Limpach.
     * 4. The name of the author may not be used to endorse or promote products
     *    derived from this software without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/bus.h>
    #include <sys/ktr.h>
    #include <sys/lock.h>
    #include <sys/mount.h>
    #include <sys/malloc.h>
    #include <sys/mutex.h>
    #include <sys/kernel.h>
    #include <sys/proc.h>
    #include <sys/reboot.h>
    #include <sys/sysproto.h>
    
    #include <machine/xen/xen-os.h>
    
    #include <vm/vm.h>
    #include <vm/pmap.h>
    #include <machine/segments.h>
    #include <machine/pcb.h>
    #include <machine/stdarg.h>
    #include <machine/vmparam.h>
    #include <machine/cpu.h>
    #include <machine/intr_machdep.h>
    #include <machine/md_var.h>
    #include <machine/asmacros.h>
    
    
    
    #include <xen/hypervisor.h>
    #include <machine/xen/xenvar.h>
    #include <machine/xen/xenfunc.h>
    #include <machine/xen/xenpmap.h>
    #include <machine/xen/xenfunc.h>
    #include <xen/interface/memory.h>
    #include <machine/xen/features.h>
    #ifdef SMP
    #include <machine/privatespace.h>
    #endif
    
    
    #include <vm/vm_page.h>
    
    
    #define IDTVEC(name)    __CONCAT(X,name)
    
    extern inthand_t
    IDTVEC(div), IDTVEC(dbg), IDTVEC(nmi), IDTVEC(bpt), IDTVEC(ofl),
            IDTVEC(bnd), IDTVEC(ill), IDTVEC(dna), IDTVEC(fpusegm),
            IDTVEC(tss), IDTVEC(missing), IDTVEC(stk), IDTVEC(prot),
            IDTVEC(page), IDTVEC(mchk), IDTVEC(rsvd), IDTVEC(fpu), IDTVEC(align),
            IDTVEC(xmm), IDTVEC(lcall_syscall), IDTVEC(int0x80_syscall);
    
    
    int xendebug_flags; 
    start_info_t *xen_start_info;
    shared_info_t *HYPERVISOR_shared_info;
    xen_pfn_t *xen_machine_phys = machine_to_phys_mapping;
    xen_pfn_t *xen_phys_machine;
    xen_pfn_t *xen_pfn_to_mfn_frame_list[16];
    xen_pfn_t *xen_pfn_to_mfn_frame_list_list;
    int preemptable, init_first;
    extern unsigned int avail_space;
    
    void ni_cli(void);
   void ni_sti(void);
   
   
   void
   ni_cli(void)
   {
           CTR0(KTR_SPARE2, "ni_cli disabling interrupts");
           __asm__("pushl %edx;"
                   "pushl %eax;"
                   );
           __cli();
           __asm__("popl %eax;"
                   "popl %edx;"
                   );
   }
   
   
   void
   ni_sti(void)
   {
           __asm__("pushl %edx;"
                   "pushl %esi;"
                   "pushl %eax;"
                   );
           __sti();
           __asm__("popl %eax;"
                   "popl %esi;"
                   "popl %edx;"
                   );
   }
   
   /*
    * Modify the cmd_line by converting ',' to NULLs so that it is in a  format 
    * suitable for the static env vars.
    */
   char *
   xen_setbootenv(char *cmd_line)
   {
           char *cmd_line_next;
       
           /* Skip leading spaces */
           for (; *cmd_line == ' '; cmd_line++);
   
           printk("xen_setbootenv(): cmd_line='%s'\n", cmd_line);
   
           for (cmd_line_next = cmd_line; strsep(&cmd_line_next, ",") != NULL;);
           return cmd_line;
   }
   
   static struct 
   {
           const char      *ev;
           int             mask;
   } howto_names[] = {
           {"boot_askname",        RB_ASKNAME},
           {"boot_single", RB_SINGLE},
           {"boot_nosync", RB_NOSYNC},
           {"boot_halt",   RB_ASKNAME},
           {"boot_serial", RB_SERIAL},
           {"boot_cdrom",  RB_CDROM},
           {"boot_gdb",    RB_GDB},
           {"boot_gdb_pause",      RB_RESERVED1},
           {"boot_verbose",        RB_VERBOSE},
           {"boot_multicons",      RB_MULTIPLE},
           {NULL,  0}
   };
   
   int 
   xen_boothowto(char *envp)
   {
           int i, howto = 0;
   
           /* get equivalents from the environment */
           for (i = 0; howto_names[i].ev != NULL; i++)
                   if (getenv(howto_names[i].ev) != NULL)
                           howto |= howto_names[i].mask;
           return howto;
   }
   
   #define PRINTK_BUFSIZE 1024
   void
   printk(const char *fmt, ...)
   {
           __va_list ap;
           int retval;
           static char buf[PRINTK_BUFSIZE];
   
           va_start(ap, fmt);
           retval = vsnprintf(buf, PRINTK_BUFSIZE - 1, fmt, ap);
           va_end(ap);
           buf[retval] = 0;
           (void)HYPERVISOR_console_write(buf, retval);
   }
   
   
   #define XPQUEUE_SIZE 128
   
   struct mmu_log {
           char *file;
           int line;
   };
   
   #ifdef SMP
   /* per-cpu queues and indices */
   #ifdef INVARIANTS
   static struct mmu_log xpq_queue_log[MAX_VIRT_CPUS][XPQUEUE_SIZE];
   #endif
   
   static int xpq_idx[MAX_VIRT_CPUS];  
   static mmu_update_t xpq_queue[MAX_VIRT_CPUS][XPQUEUE_SIZE];
   
   #define XPQ_QUEUE_LOG xpq_queue_log[vcpu]
   #define XPQ_QUEUE xpq_queue[vcpu]
   #define XPQ_IDX xpq_idx[vcpu]
   #define SET_VCPU() int vcpu = smp_processor_id()
   #else
           
   static mmu_update_t xpq_queue[XPQUEUE_SIZE];
   #ifdef INVARIANTS
   static struct mmu_log xpq_queue_log[XPQUEUE_SIZE];
   #endif
   static int xpq_idx = 0;
   
   #define XPQ_QUEUE_LOG xpq_queue_log
   #define XPQ_QUEUE xpq_queue
   #define XPQ_IDX xpq_idx
   #define SET_VCPU()
   #endif /* !SMP */
   
   #define XPQ_IDX_INC atomic_add_int(&XPQ_IDX, 1);
   
   #if 0
   static void
   xen_dump_queue(void)
   {
           int _xpq_idx = XPQ_IDX;
           int i;
   
           if (_xpq_idx <= 1)
                   return;
   
           printk("xen_dump_queue(): %u entries\n", _xpq_idx);
           for (i = 0; i < _xpq_idx; i++) {
                   printk(" val: %llx ptr: %llx\n", XPQ_QUEUE[i].val, XPQ_QUEUE[i].ptr);
           }
   }
   #endif
   
   
   static __inline void
   _xen_flush_queue(void)
   {
           SET_VCPU();
           int _xpq_idx = XPQ_IDX;
           int error, i;
   
   #ifdef INVARIANTS
           if (__predict_true(gdtset))
                   CRITICAL_ASSERT(curthread);
   #endif
   
           XPQ_IDX = 0;
           /* Make sure index is cleared first to avoid double updates. */
           error = HYPERVISOR_mmu_update((mmu_update_t *)&XPQ_QUEUE,
                                         _xpq_idx, NULL, DOMID_SELF);
       
   #if 0
           if (__predict_true(gdtset))
           for (i = _xpq_idx; i > 0;) {
                   if (i >= 3) {
                           CTR6(KTR_PMAP, "mmu:val: %lx ptr: %lx val: %lx "
                               "ptr: %lx val: %lx ptr: %lx",
                               (XPQ_QUEUE[i-1].val & 0xffffffff),
                               (XPQ_QUEUE[i-1].ptr & 0xffffffff),
                               (XPQ_QUEUE[i-2].val & 0xffffffff),
                               (XPQ_QUEUE[i-2].ptr & 0xffffffff),
                               (XPQ_QUEUE[i-3].val & 0xffffffff),
                               (XPQ_QUEUE[i-3].ptr & 0xffffffff));
                               i -= 3;
                   } else if (i == 2) {
                           CTR4(KTR_PMAP, "mmu: val: %lx ptr: %lx val: %lx ptr: %lx",
                               (XPQ_QUEUE[i-1].val & 0xffffffff),
                               (XPQ_QUEUE[i-1].ptr & 0xffffffff),
                               (XPQ_QUEUE[i-2].val & 0xffffffff),
                               (XPQ_QUEUE[i-2].ptr & 0xffffffff));
                           i = 0;
                   } else {
                           CTR2(KTR_PMAP, "mmu: val: %lx ptr: %lx", 
                               (XPQ_QUEUE[i-1].val & 0xffffffff),
                               (XPQ_QUEUE[i-1].ptr & 0xffffffff));
                           i = 0;
                   }
           }
   #endif  
           if (__predict_false(error < 0)) {
                   for (i = 0; i < _xpq_idx; i++)
                           printf("val: %llx ptr: %llx\n",
                               XPQ_QUEUE[i].val, XPQ_QUEUE[i].ptr);
                   panic("Failed to execute MMU updates: %d", error);
           }
   
   }
   
   void
   xen_flush_queue(void)
   {
           SET_VCPU();
   
           if (__predict_true(gdtset))
                   critical_enter();
           if (XPQ_IDX != 0) _xen_flush_queue();
           if (__predict_true(gdtset))
                   critical_exit();
   }
   
   static __inline void
   xen_increment_idx(void)
   {
           SET_VCPU();
   
           XPQ_IDX++;
           if (__predict_false(XPQ_IDX == XPQUEUE_SIZE))
                   xen_flush_queue();
   }
   
   void
   xen_check_queue(void)
   {
   #ifdef INVARIANTS
           SET_VCPU();
           
           KASSERT(XPQ_IDX == 0, ("pending operations XPQ_IDX=%d", XPQ_IDX));
   #endif
   }
   
   void
   xen_invlpg(vm_offset_t va)
   {
           struct mmuext_op op;
           op.cmd = MMUEXT_INVLPG_ALL;
           op.arg1.linear_addr = va & ~PAGE_MASK;
           PANIC_IF(HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF) < 0);
   }
   
   void
   xen_load_cr3(u_int val)
   {
           struct mmuext_op op;
   #ifdef INVARIANTS
           SET_VCPU();
           
           KASSERT(XPQ_IDX == 0, ("pending operations XPQ_IDX=%d", XPQ_IDX));
   #endif
           op.cmd = MMUEXT_NEW_BASEPTR;
           op.arg1.mfn = xpmap_ptom(val) >> PAGE_SHIFT;
           PANIC_IF(HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF) < 0);
   }
   
   #ifdef KTR
   static __inline u_int
   rebp(void)
   {
           u_int   data;
   
           __asm __volatile("movl 4(%%ebp),%0" : "=r" (data));     
           return (data);
   }
   #endif
   
   u_int
   read_eflags(void)
   {
           vcpu_info_t *_vcpu;
           u_int eflags;
   
           eflags = _read_eflags();
           _vcpu = &HYPERVISOR_shared_info->vcpu_info[smp_processor_id()]; 
           if (_vcpu->evtchn_upcall_mask)
                   eflags &= ~PSL_I;
   
           return (eflags);
   }
   
   void
   write_eflags(u_int eflags)
   {
           u_int intr;
   
           CTR2(KTR_SPARE2, "%x xen_restore_flags eflags %x", rebp(), eflags);
           intr = ((eflags & PSL_I) == 0);
           __restore_flags(intr);
           _write_eflags(eflags);
   }
   
   void
   xen_cli(void)
   {
           CTR1(KTR_SPARE2, "%x xen_cli disabling interrupts", rebp());
           __cli();
   }
   
   void
   xen_sti(void)
   {
           CTR1(KTR_SPARE2, "%x xen_sti enabling interrupts", rebp());
           __sti();
   }
   
   u_int
   xen_rcr2(void)
   {
   
           return (HYPERVISOR_shared_info->vcpu_info[curcpu].arch.cr2);
   }
   
   void
   _xen_machphys_update(vm_paddr_t mfn, vm_paddr_t pfn, char *file, int line)
   {
           SET_VCPU();
           
           if (__predict_true(gdtset))
                   critical_enter();
           XPQ_QUEUE[XPQ_IDX].ptr = (mfn << PAGE_SHIFT) | MMU_MACHPHYS_UPDATE;
           XPQ_QUEUE[XPQ_IDX].val = pfn;
   #ifdef INVARIANTS
           XPQ_QUEUE_LOG[XPQ_IDX].file = file;
           XPQ_QUEUE_LOG[XPQ_IDX].line = line;     
   #endif          
           xen_increment_idx();
           if (__predict_true(gdtset))
                   critical_exit();
   }
   
   void
   _xen_queue_pt_update(vm_paddr_t ptr, vm_paddr_t val, char *file, int line)
   {
           SET_VCPU();
   
           if (__predict_true(gdtset))     
                   mtx_assert(&vm_page_queue_mtx, MA_OWNED);
   
           KASSERT((ptr & 7) == 0, ("misaligned update"));
           
           if (__predict_true(gdtset))
                   critical_enter();
           
           XPQ_QUEUE[XPQ_IDX].ptr = ((uint64_t)ptr) | MMU_NORMAL_PT_UPDATE;
           XPQ_QUEUE[XPQ_IDX].val = (uint64_t)val;
   #ifdef INVARIANTS
           XPQ_QUEUE_LOG[XPQ_IDX].file = file;
           XPQ_QUEUE_LOG[XPQ_IDX].line = line;     
   #endif  
           xen_increment_idx();
           if (__predict_true(gdtset))
                   critical_exit();
   }
   
   void 
   xen_pgdpt_pin(vm_paddr_t ma)
   {
           struct mmuext_op op;
           op.cmd = MMUEXT_PIN_L3_TABLE;
           op.arg1.mfn = ma >> PAGE_SHIFT;
           xen_flush_queue();
           PANIC_IF(HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF) < 0);
   }
   
   void 
   xen_pgd_pin(vm_paddr_t ma)
   {
           struct mmuext_op op;
           op.cmd = MMUEXT_PIN_L2_TABLE;
           op.arg1.mfn = ma >> PAGE_SHIFT;
           xen_flush_queue();
           PANIC_IF(HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF) < 0);
   }
   
   void 
   xen_pgd_unpin(vm_paddr_t ma)
   {
           struct mmuext_op op;
           op.cmd = MMUEXT_UNPIN_TABLE;
           op.arg1.mfn = ma >> PAGE_SHIFT;
           xen_flush_queue();
           PANIC_IF(HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF) < 0);
   }
   
   void 
   xen_pt_pin(vm_paddr_t ma)
   {
           struct mmuext_op op;
           op.cmd = MMUEXT_PIN_L1_TABLE;
           op.arg1.mfn = ma >> PAGE_SHIFT;
           xen_flush_queue();
           PANIC_IF(HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF) < 0);
   }
   
   void 
   xen_pt_unpin(vm_paddr_t ma)
   {
           struct mmuext_op op;
           op.cmd = MMUEXT_UNPIN_TABLE;
           op.arg1.mfn = ma >> PAGE_SHIFT;
           xen_flush_queue();
           PANIC_IF(HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF) < 0);
   }
   
   void 
   xen_set_ldt(vm_paddr_t ptr, unsigned long len)
   {
           struct mmuext_op op;
           op.cmd = MMUEXT_SET_LDT;
           op.arg1.linear_addr = ptr;
           op.arg2.nr_ents = len;
           xen_flush_queue();
           PANIC_IF(HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF) < 0);
   }
   
   void xen_tlb_flush(void)
   {
           struct mmuext_op op;
           op.cmd = MMUEXT_TLB_FLUSH_LOCAL;
           xen_flush_queue();
           PANIC_IF(HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF) < 0);
   }
   
   void
   xen_update_descriptor(union descriptor *table, union descriptor *entry)
   {
           vm_paddr_t pa;
           pt_entry_t *ptp;
   
           ptp = vtopte((vm_offset_t)table);
           pa = (*ptp & PG_FRAME) | ((vm_offset_t)table & PAGE_MASK);
           if (HYPERVISOR_update_descriptor(pa, *(uint64_t *)entry))
                   panic("HYPERVISOR_update_descriptor failed\n");
   }
   
   
   #if 0
   /*
    * Bitmap is indexed by page number. If bit is set, the page is part of a
    * xen_create_contiguous_region() area of memory.
    */
   unsigned long *contiguous_bitmap;
   
   static void 
   contiguous_bitmap_set(unsigned long first_page, unsigned long nr_pages)
   {
           unsigned long start_off, end_off, curr_idx, end_idx;
   
           curr_idx  = first_page / BITS_PER_LONG;
           start_off = first_page & (BITS_PER_LONG-1);
           end_idx   = (first_page + nr_pages) / BITS_PER_LONG;
           end_off   = (first_page + nr_pages) & (BITS_PER_LONG-1);
   
           if (curr_idx == end_idx) {
                   contiguous_bitmap[curr_idx] |=
                           ((1UL<<end_off)-1) & -(1UL<<start_off);
           } else {
                   contiguous_bitmap[curr_idx] |= -(1UL<<start_off);
                   while ( ++curr_idx < end_idx )
                           contiguous_bitmap[curr_idx] = ~0UL;
                   contiguous_bitmap[curr_idx] |= (1UL<<end_off)-1;
           }
   }
   
   static void 
   contiguous_bitmap_clear(unsigned long first_page, unsigned long nr_pages)
   {
           unsigned long start_off, end_off, curr_idx, end_idx;
   
           curr_idx  = first_page / BITS_PER_LONG;
           start_off = first_page & (BITS_PER_LONG-1);
           end_idx   = (first_page + nr_pages) / BITS_PER_LONG;
           end_off   = (first_page + nr_pages) & (BITS_PER_LONG-1);
   
           if (curr_idx == end_idx) {
                   contiguous_bitmap[curr_idx] &=
                           -(1UL<<end_off) | ((1UL<<start_off)-1);
           } else {
                   contiguous_bitmap[curr_idx] &= (1UL<<start_off)-1;
                   while ( ++curr_idx != end_idx )
                           contiguous_bitmap[curr_idx] = 0;
                   contiguous_bitmap[curr_idx] &= -(1UL<<end_off);
           }
   }
   #endif
   
   /* Ensure multi-page extents are contiguous in machine memory. */
   int 
   xen_create_contiguous_region(vm_page_t pages, int npages)
   {
           unsigned long  mfn, i, flags;
           int order;
           struct xen_memory_reservation reservation = {
                   .nr_extents   = 1,
                   .extent_order = 0,
                   .domid        = DOMID_SELF
           };
           set_xen_guest_handle(reservation.extent_start, &mfn);
           
           balloon_lock(flags);
   
           /* can currently only handle power of two allocation */
           PANIC_IF(ffs(npages) != fls(npages));
   
           /* 0. determine order */
           order = (ffs(npages) == fls(npages)) ? fls(npages) - 1 : fls(npages);
           
           /* 1. give away machine pages. */
           for (i = 0; i < (1 << order); i++) {
                   int pfn;
                   pfn = VM_PAGE_TO_PHYS(&pages[i]) >> PAGE_SHIFT;
                   mfn = PFNTOMFN(pfn);
                   PFNTOMFN(pfn) = INVALID_P2M_ENTRY;
                   PANIC_IF(HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation) != 1);
           }
   
   
           /* 2. Get a new contiguous memory extent. */
           reservation.extent_order = order;
           /* xenlinux hardcodes this because of aacraid - maybe set to 0 if we're not 
            * running with a broxen driver XXXEN
            */
           reservation.address_bits = 31; 
           if (HYPERVISOR_memory_op(XENMEM_increase_reservation, &reservation) != 1)
                   goto fail;
   
           /* 3. Map the new extent in place of old pages. */
           for (i = 0; i < (1 << order); i++) {
                   int pfn;
                   pfn = VM_PAGE_TO_PHYS(&pages[i]) >> PAGE_SHIFT;
                   xen_machphys_update(mfn+i, pfn);
                   PFNTOMFN(pfn) = mfn+i;
           }
   
           xen_tlb_flush();
   
   #if 0
           contiguous_bitmap_set(VM_PAGE_TO_PHYS(&pages[0]) >> PAGE_SHIFT, 1UL << order);
   #endif
   
           balloon_unlock(flags);
   
           return 0;
   
    fail:
           reservation.extent_order = 0;
           reservation.address_bits = 0;
   
           for (i = 0; i < (1 << order); i++) {
                   int pfn;
                   pfn = VM_PAGE_TO_PHYS(&pages[i]) >> PAGE_SHIFT;
                   PANIC_IF(HYPERVISOR_memory_op(
                           XENMEM_increase_reservation, &reservation) != 1);
                   xen_machphys_update(mfn, pfn);
                   PFNTOMFN(pfn) = mfn;
           }
   
           xen_tlb_flush();
   
           balloon_unlock(flags);
   
           return ENOMEM;
   }
   
   void 
   xen_destroy_contiguous_region(void *addr, int npages)
   {
           unsigned long  mfn, i, flags, order, pfn0;
           struct xen_memory_reservation reservation = {
                   .nr_extents   = 1,
                   .extent_order = 0,
                   .domid        = DOMID_SELF
           };
           set_xen_guest_handle(reservation.extent_start, &mfn);
           
           pfn0 = vtophys(addr) >> PAGE_SHIFT;
   #if 0
           scrub_pages(vstart, 1 << order);
   #endif
           /* can currently only handle power of two allocation */
           PANIC_IF(ffs(npages) != fls(npages));
   
           /* 0. determine order */
           order = (ffs(npages) == fls(npages)) ? fls(npages) - 1 : fls(npages);
   
           balloon_lock(flags);
   
   #if 0
           contiguous_bitmap_clear(vtophys(addr) >> PAGE_SHIFT, 1UL << order);
   #endif
   
           /* 1. Zap current PTEs, giving away the underlying pages. */
           for (i = 0; i < (1 << order); i++) {
                   int pfn;
                   uint64_t new_val = 0;
                   pfn = vtomach((char *)addr + i*PAGE_SIZE) >> PAGE_SHIFT;
   
                   PANIC_IF(HYPERVISOR_update_va_mapping((vm_offset_t)((char *)addr + (i * PAGE_SIZE)), new_val, 0));
                   PFNTOMFN(pfn) = INVALID_P2M_ENTRY;
                   PANIC_IF(HYPERVISOR_memory_op(
                           XENMEM_decrease_reservation, &reservation) != 1);
           }
   
           /* 2. Map new pages in place of old pages. */
           for (i = 0; i < (1 << order); i++) {
                   int pfn;
                   uint64_t new_val;
                   pfn = pfn0 + i;
                   PANIC_IF(HYPERVISOR_memory_op(XENMEM_increase_reservation, &reservation) != 1);
                   
                   new_val = mfn << PAGE_SHIFT;
                   PANIC_IF(HYPERVISOR_update_va_mapping((vm_offset_t)addr + (i * PAGE_SIZE), 
                                                         new_val, PG_KERNEL));
                   xen_machphys_update(mfn, pfn);
                   PFNTOMFN(pfn) = mfn;
           }
   
           xen_tlb_flush();
   
           balloon_unlock(flags);
   }
   
   extern unsigned long cpu0prvpage;
   extern unsigned long *SMPpt;
   extern  struct user     *proc0uarea;
   extern  vm_offset_t     proc0kstack;
   extern int vm86paddr, vm86phystk;
   char *bootmem_start, *bootmem_current, *bootmem_end;
   
   pteinfo_t *pteinfo_list;
   void initvalues(start_info_t *startinfo);
   
   struct xenstore_domain_interface;
   extern struct xenstore_domain_interface *xen_store;
   
   char *console_page;
   
   void *
   bootmem_alloc(unsigned int size) 
   {
           char *retptr;
           
           retptr = bootmem_current;
           PANIC_IF(retptr + size > bootmem_end);
           bootmem_current += size;
   
           return retptr;
   }
   
   void 
   bootmem_free(void *ptr, unsigned int size) 
   {
           char *tptr;
           
           tptr = ptr;
           PANIC_IF(tptr != bootmem_current - size ||
                   bootmem_current - size < bootmem_start);        
   
           bootmem_current -= size;
   }
   
   #if 0
   static vm_paddr_t
   xpmap_mtop2(vm_paddr_t mpa)
   {
           return ((machine_to_phys_mapping[mpa >> PAGE_SHIFT] << PAGE_SHIFT)
               ) | (mpa & ~PG_FRAME);
   }
   
   static pd_entry_t 
   xpmap_get_bootpde(vm_paddr_t va)
   {
   
           return ((pd_entry_t *)xen_start_info->pt_base)[va >> 22];
   }
   
   static pd_entry_t
   xpmap_get_vbootpde(vm_paddr_t va)
   {
           pd_entry_t pde;
   
           pde = xpmap_get_bootpde(va);
           if ((pde & PG_V) == 0)
                   return (pde & ~PG_FRAME);
           return (pde & ~PG_FRAME) |
                   (xpmap_mtop2(pde & PG_FRAME) + KERNBASE);
   }
   
   static pt_entry_t 8*
   xpmap_get_bootptep(vm_paddr_t va)
   {
           pd_entry_t pde;
   
           pde = xpmap_get_vbootpde(va);
           if ((pde & PG_V) == 0)
                   return (void *)-1;
   #define PT_MASK         0x003ff000      /* page table address bits */
           return &(((pt_entry_t *)(pde & PG_FRAME))[(va & PT_MASK) >> PAGE_SHIFT]);
   }
   
   static pt_entry_t
   xpmap_get_bootpte(vm_paddr_t va)
   {
   
           return xpmap_get_bootptep(va)[0];
   }
   #endif
   
   
   #ifdef ADD_ISA_HOLE
   static void
   shift_phys_machine(unsigned long *phys_machine, int nr_pages)
   {
   
           unsigned long *tmp_page, *current_page, *next_page;
           int i;
   
           tmp_page = bootmem_alloc(PAGE_SIZE);
           current_page = phys_machine + nr_pages - (PAGE_SIZE/sizeof(unsigned long));  
           next_page = current_page - (PAGE_SIZE/sizeof(unsigned long));  
           bcopy(phys_machine, tmp_page, PAGE_SIZE);
   
           while (current_page > phys_machine) { 
                   /*  save next page */
                   bcopy(next_page, tmp_page, PAGE_SIZE);
                   /* shift down page */
                   bcopy(current_page, next_page, PAGE_SIZE);
                   /*  finish swap */
                   bcopy(tmp_page, current_page, PAGE_SIZE);
             
                   current_page -= (PAGE_SIZE/sizeof(unsigned long));
                   next_page -= (PAGE_SIZE/sizeof(unsigned long));
           }
           bootmem_free(tmp_page, PAGE_SIZE);      
           
           for (i = 0; i < nr_pages; i++) {
                   xen_machphys_update(phys_machine[i], i);
           }
           memset(phys_machine, INVALID_P2M_ENTRY, PAGE_SIZE);
   
   }
   #endif /* ADD_ISA_HOLE */
   
   /*
    * Build a directory of the pages that make up our Physical to Machine
    * mapping table. The Xen suspend/restore code uses this to find our
    * mapping table.
    */
   static void
   init_frame_list_list(void *arg)
   {
           unsigned long nr_pages = xen_start_info->nr_pages;
   #define FPP     (PAGE_SIZE/sizeof(xen_pfn_t))
           int i, j, k;
   
           xen_pfn_to_mfn_frame_list_list = malloc(PAGE_SIZE, M_DEVBUF, M_WAITOK);
           for (i = 0, j = 0, k = -1; i < nr_pages;
                i += FPP, j++) {
                   if ((j & (FPP - 1)) == 0) {
                           k++;
                           xen_pfn_to_mfn_frame_list[k] =
                                   malloc(PAGE_SIZE, M_DEVBUF, M_WAITOK);
                           xen_pfn_to_mfn_frame_list_list[k] =
                                   VTOMFN(xen_pfn_to_mfn_frame_list[k]);
                           j = 0;
                   }
                   xen_pfn_to_mfn_frame_list[k][j] = 
                           VTOMFN(&xen_phys_machine[i]);
           }
   
           HYPERVISOR_shared_info->arch.max_pfn = nr_pages;
           HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list
                   = VTOMFN(xen_pfn_to_mfn_frame_list_list);
   }       
   SYSINIT(init_fll, SI_SUB_DEVFS, SI_ORDER_ANY, init_frame_list_list, NULL);
   
   extern unsigned long physfree;
   
   int pdir, curoffset;
   extern int nkpt;
   
   void
   initvalues(start_info_t *startinfo)
   { 
           int l3_pages, l2_pages, l1_pages, offset;
           vm_offset_t cur_space, cur_space_pt;
           struct physdev_set_iopl set_iopl;
           
           vm_paddr_t KPTphys, IdlePTDma;
           vm_paddr_t console_page_ma, xen_store_ma;
           vm_offset_t KPTphysoff, tmpva;
           vm_paddr_t shinfo;
   #ifdef PAE
           vm_paddr_t IdlePDPTma, IdlePDPTnewma;
           vm_paddr_t IdlePTDnewma[4];
           pd_entry_t *IdlePDPTnew, *IdlePTDnew;
   #else
           vm_paddr_t pdir_shadow_ma;
   #endif
           unsigned long i;
           int ncpus = MAXCPU;
   
           nkpt = min(
                   min(
                           max((startinfo->nr_pages >> NPGPTD_SHIFT), nkpt),
                       NPGPTD*NPDEPG - KPTDI),
                       (HYPERVISOR_VIRT_START - KERNBASE) >> PDRSHIFT);
   
           HYPERVISOR_vm_assist(VMASST_CMD_enable, VMASST_TYPE_4gb_segments);      
   #ifdef notyet
           /*
            * need to install handler
            */
           HYPERVISOR_vm_assist(VMASST_CMD_enable, VMASST_TYPE_4gb_segments_notify);       
   #endif  
           xen_start_info = startinfo;
           xen_phys_machine = (xen_pfn_t *)startinfo->mfn_list;
   
           IdlePTD = (pd_entry_t *)((uint8_t *)startinfo->pt_base + PAGE_SIZE);
           l1_pages = 0;
           
   #ifdef PAE
           l3_pages = 1;
           l2_pages = 0;
           IdlePDPT = (pd_entry_t *)startinfo->pt_base;
           IdlePDPTma = xpmap_ptom(VTOP(startinfo->pt_base));
           for (i = (KERNBASE >> 30);
                (i < 4) && (IdlePDPT[i] != 0); i++)
                           l2_pages++;
           /*
            * Note that only one page directory has been allocated at this point.
            * Thus, if KERNBASE
            */
   #if 0
           for (i = 0; i < l2_pages; i++)
                   IdlePTDma[i] = xpmap_ptom(VTOP(IdlePTD + i*PAGE_SIZE));
   #endif
           
           l2_pages = (l2_pages == 0) ? 1 : l2_pages;
   #else   
           l3_pages = 0;
           l2_pages = 1;
   #endif
           for (i = (((KERNBASE>>18) & PAGE_MASK)>>PAGE_SHIFT);
                (i<l2_pages*NPDEPG) && (i<(VM_MAX_KERNEL_ADDRESS>>PDRSHIFT)); i++) {
                   
                   if (IdlePTD[i] == 0)
                           break;
                   l1_pages++;
           }
           
           /* number of pages allocated after the pts + 1*/;
           cur_space = xen_start_info->pt_base +
               ((xen_start_info->nr_pt_frames) + 3 )*PAGE_SIZE;
           printk("initvalues(): wooh - availmem=%x,%x\n", avail_space, cur_space);
   
           printk("KERNBASE=%x,pt_base=%x, VTOPFN(base)=%x, nr_pt_frames=%x\n",
               KERNBASE,xen_start_info->pt_base, VTOPFN(xen_start_info->pt_base),
               xen_start_info->nr_pt_frames);
           xendebug_flags = 0; /* 0xffffffff; */
   
           /* allocate 4 pages for bootmem allocator */
           bootmem_start = bootmem_current = (char *)cur_space;
           cur_space += (4 * PAGE_SIZE);
           bootmem_end = (char *)cur_space;
   
           /* allocate page for gdt */
           gdt = (union descriptor *)cur_space;
           cur_space += PAGE_SIZE*ncpus;
   
           /* allocate page for ldt */
           ldt = (union descriptor *)cur_space; cur_space += PAGE_SIZE;
           cur_space += PAGE_SIZE;
           
           HYPERVISOR_shared_info = (shared_info_t *)cur_space;
           cur_space += PAGE_SIZE;
   
           xen_store = (struct xenstore_domain_interface *)cur_space;
           cur_space += PAGE_SIZE;
   
           console_page = (char *)cur_space;
           cur_space += PAGE_SIZE;
   
   #ifdef ADD_ISA_HOLE
           shift_phys_machine(xen_phys_machine, xen_start_info->nr_pages);
   #endif
           /* 
            * pre-zero unused mapped pages - mapped on 4MB boundary
            */
   #ifdef PAE
           IdlePDPT = (pd_entry_t *)startinfo->pt_base;
           IdlePDPTma = xpmap_ptom(VTOP(startinfo->pt_base));
           /*
            * Note that only one page directory has been allocated at this point.
            * Thus, if KERNBASE
            */
           IdlePTD = (pd_entry_t *)((uint8_t *)startinfo->pt_base + PAGE_SIZE);
          IdlePTDma = xpmap_ptom(VTOP(IdlePTD));
          l3_pages = 1;
  #else   
          IdlePTD = (pd_entry_t *)startinfo->pt_base;
          IdlePTDma = xpmap_ptom(VTOP(startinfo->pt_base));
          l3_pages = 0;
  #endif
          l2_pages = 1;
          l1_pages = xen_start_info->nr_pt_frames - l2_pages - l3_pages;
  
          KPTphysoff = (l2_pages + l3_pages)*PAGE_SIZE;
  
          KPTphys = xpmap_ptom(VTOP(startinfo->pt_base + KPTphysoff));
          XENPRINTF("IdlePTD %p\n", IdlePTD);
          XENPRINTF("nr_pages: %ld shared_info: 0x%lx flags: 0x%lx pt_base: 0x%lx "
                    "mod_start: 0x%lx mod_len: 0x%lx\n",
                    xen_start_info->nr_pages, xen_start_info->shared_info, 
                    xen_start_info->flags, xen_start_info->pt_base, 
                    xen_start_info->mod_start, xen_start_info->mod_len);
          /* Map proc0's KSTACK */
  
          proc0kstack = cur_space; cur_space += (KSTACK_PAGES * PAGE_SIZE);
          printk("proc0kstack=%u\n", proc0kstack);
  
          /* vm86/bios stack */
          cur_space += PAGE_SIZE;
  
          /* Map space for the vm86 region */
          vm86paddr = (vm_offset_t)cur_space;
          cur_space += (PAGE_SIZE * 3);
  
  #ifdef PAE
          IdlePDPTnew = (pd_entry_t *)cur_space; cur_space += PAGE_SIZE;
          bzero(IdlePDPTnew, PAGE_SIZE);
  
          IdlePDPTnewma =  xpmap_ptom(VTOP(IdlePDPTnew));
          IdlePTDnew = (pd_entry_t *)cur_space; cur_space += 4*PAGE_SIZE;
          bzero(IdlePTDnew, 4*PAGE_SIZE);
  
          for (i = 0; i < 4; i++) 
                  IdlePTDnewma[i] =
                      xpmap_ptom(VTOP((uint8_t *)IdlePTDnew + i*PAGE_SIZE));
          /*
           * L3
           *
           * Copy the 4 machine addresses of the new PTDs in to the PDPT
           * 
           */
          for (i = 0; i < 4; i++)
                  IdlePDPTnew[i] = IdlePTDnewma[i] | PG_V;
  
          __asm__("nop;");
          /*
           *
           * re-map the new PDPT read-only
           */
          PT_SET_MA(IdlePDPTnew, IdlePDPTnewma | PG_V);
          /*
           * 
           * Unpin the current PDPT
           */
          xen_pt_unpin(IdlePDPTma);
          
          for (i = 0; i < 20; i++) {
                  int startidx = ((KERNBASE >> 18) & PAGE_MASK) >> 3;
  
                  if (IdlePTD[startidx + i] == 0) {
                          l1_pages = i;
                          break;
                  }       
          }
  
  #endif  /* PAE */
          
          /* unmap remaining pages from initial 4MB chunk
           *
           */
          for (tmpva = cur_space; (tmpva & ((1<<22)-1)) != 0; tmpva += PAGE_SIZE) {
                  bzero((char *)tmpva, PAGE_SIZE);
                  PT_SET_MA(tmpva, (vm_paddr_t)0);
          }
          
          PT_UPDATES_FLUSH();
  
          memcpy(((uint8_t *)IdlePTDnew) + ((unsigned int)(KERNBASE >> 18)),
              ((uint8_t *)IdlePTD) + ((KERNBASE >> 18) & PAGE_MASK),
              l1_pages*sizeof(pt_entry_t));
  
          for (i = 0; i < 4; i++) {
                  PT_SET_MA((uint8_t *)IdlePTDnew + i*PAGE_SIZE,
                      IdlePTDnewma[i] | PG_V);
          }
          xen_load_cr3(VTOP(IdlePDPTnew));
          xen_pgdpt_pin(xpmap_ptom(VTOP(IdlePDPTnew)));
  
          /* allocate remainder of nkpt pages */
          cur_space_pt = cur_space;
          for (offset = (KERNBASE >> PDRSHIFT), i = l1_pages; i < nkpt;
               i++, cur_space += PAGE_SIZE) {
                  pdir = (offset + i) / NPDEPG;
                  curoffset = ((offset + i) % NPDEPG);
                  if (((offset + i) << PDRSHIFT) == VM_MAX_KERNEL_ADDRESS)
                          break;
  
                  /*
                   * make sure that all the initial page table pages
                   * have been zeroed
                   */
                  PT_SET_MA(cur_space_pt,
                      xpmap_ptom(VTOP(cur_space)) | PG_V | PG_RW);
                  bzero((char *)cur_space_pt, PAGE_SIZE);
                  PT_SET_MA(cur_space_pt, (vm_paddr_t)0);
                  xen_pt_pin(xpmap_ptom(VTOP(cur_space)));
                  xen_queue_pt_update((vm_paddr_t)(IdlePTDnewma[pdir] +
                          curoffset*sizeof(vm_paddr_t)), 
                      xpmap_ptom(VTOP(cur_space)) | PG_KERNEL);
                  PT_UPDATES_FLUSH();
          }
          
          for (i = 0; i < 4; i++) {
                  pdir = (PTDPTDI + i) / NPDEPG;
                  curoffset = (PTDPTDI + i) % NPDEPG;
  
                  xen_queue_pt_update((vm_paddr_t)(IdlePTDnewma[pdir] +
                          curoffset*sizeof(vm_paddr_t)), 
                      IdlePTDnewma[i] | PG_V);
          }
  
          PT_UPDATES_FLUSH();
          
          IdlePTD = IdlePTDnew;
          IdlePDPT = IdlePDPTnew;
          IdlePDPTma = IdlePDPTnewma;
          
          /*
           * shared_info is an unsigned long so this will randomly break if
           * it is allocated above 4GB - I guess people are used to that
           * sort of thing with Xen ... sigh
           */
          shinfo = xen_start_info->shared_info;
          PT_SET_MA(HYPERVISOR_shared_info, shinfo | PG_KERNEL);
          
          printk("#4\n");
  
          xen_store_ma = (((vm_paddr_t)xen_start_info->store_mfn) << PAGE_SHIFT);
          PT_SET_MA(xen_store, xen_store_ma | PG_KERNEL);
          console_page_ma = (((vm_paddr_t)xen_start_info->console.domU.mfn) << PAGE_SHIFT);
          PT_SET_MA(console_page, console_page_ma | PG_KERNEL);
  
          printk("#5\n");
  
          set_iopl.iopl = 1;
          PANIC_IF(HYPERVISOR_physdev_op(PHYSDEVOP_SET_IOPL, &set_iopl));
          printk("#6\n");
  #if 0
          /* add page table for KERNBASE */
          xen_queue_pt_update(IdlePTDma + KPTDI*sizeof(vm_paddr_t), 
                              xpmap_ptom(VTOP(cur_space) | PG_KERNEL));
          xen_flush_queue();
  #ifdef PAE      
          xen_queue_pt_update(pdir_shadow_ma[3] + KPTDI*sizeof(vm_paddr_t), 
                              xpmap_ptom(VTOP(cur_space) | PG_V | PG_A));
  #else
          xen_queue_pt_update(pdir_shadow_ma + KPTDI*sizeof(vm_paddr_t), 
                              xpmap_ptom(VTOP(cur_space) | PG_V | PG_A));
  #endif  
          xen_flush_queue();
          cur_space += PAGE_SIZE;
          printk("#6\n");
  #endif /* 0 */  
  #ifdef notyet
          if (xen_start_info->flags & SIF_INITDOMAIN) {
                  /* Map first megabyte */
                  for (i = 0; i < (256 << PAGE_SHIFT); i += PAGE_SIZE) 
                          PT_SET_MA(KERNBASE + i, i | PG_KERNEL | PG_NC_PCD);
                  xen_flush_queue();
          }
  #endif
          /*
           * re-map kernel text read-only
           *
           */
          for (i = (((vm_offset_t)&btext) & ~PAGE_MASK);
               i < (((vm_offset_t)&etext) & ~PAGE_MASK); i += PAGE_SIZE)
                  PT_SET_MA(i, xpmap_ptom(VTOP(i)) | PG_V | PG_A);
          
          printk("#7\n");
          physfree = VTOP(cur_space);
          init_first = physfree >> PAGE_SHIFT;
          IdlePTD = (pd_entry_t *)VTOP(IdlePTD);
          IdlePDPT = (pd_entry_t *)VTOP(IdlePDPT);
          setup_xen_features();
          printk("#8, proc0kstack=%u\n", proc0kstack);
  }
  
  
  trap_info_t trap_table[] = {
          { 0,   0, GSEL(GCODE_SEL, SEL_KPL), (unsigned long) &IDTVEC(div)},
          { 1,   0|4, GSEL(GCODE_SEL, SEL_KPL), (unsigned long) &IDTVEC(dbg)},
          { 3,   3|4, GSEL(GCODE_SEL, SEL_KPL), (unsigned long) &IDTVEC(bpt)},
          { 4,   3, GSEL(GCODE_SEL, SEL_KPL), (unsigned long) &IDTVEC(ofl)},
          /* This is UPL on Linux and KPL on BSD */
          { 5,   3, GSEL(GCODE_SEL, SEL_KPL), (unsigned long) &IDTVEC(bnd)},
          { 6,   0, GSEL(GCODE_SEL, SEL_KPL), (unsigned long) &IDTVEC(ill)},
          { 7,   0|4, GSEL(GCODE_SEL, SEL_KPL), (unsigned long) &IDTVEC(dna)},
          /*
           * { 8,   0, GSEL(GCODE_SEL, SEL_KPL), (unsigned long) &IDTVEC(XXX)},
           *   no handler for double fault
           */
          { 9,   0, GSEL(GCODE_SEL, SEL_KPL), (unsigned long) &IDTVEC(fpusegm)},
          {10,   0, GSEL(GCODE_SEL, SEL_KPL), (unsigned long) &IDTVEC(tss)},
          {11,   0, GSEL(GCODE_SEL, SEL_KPL), (unsigned long) &IDTVEC(missing)},
          {12,   0, GSEL(GCODE_SEL, SEL_KPL), (unsigned long) &IDTVEC(stk)},
          {13,   0, GSEL(GCODE_SEL, SEL_KPL), (unsigned long) &IDTVEC(prot)},
          {14,   0|4, GSEL(GCODE_SEL, SEL_KPL), (unsigned long) &IDTVEC(page)},
          {15,   0, GSEL(GCODE_SEL, SEL_KPL), (unsigned long) &IDTVEC(rsvd)},
          {16,   0, GSEL(GCODE_SEL, SEL_KPL), (unsigned long) &IDTVEC(fpu)},
          {17,   0, GSEL(GCODE_SEL, SEL_KPL), (unsigned long) &IDTVEC(align)},
          {18,   0, GSEL(GCODE_SEL, SEL_KPL), (unsigned long) &IDTVEC(mchk)},
          {19,   0, GSEL(GCODE_SEL, SEL_KPL), (unsigned long) &IDTVEC(xmm)},
          {0x80, 3, GSEL(GCODE_SEL, SEL_KPL), (unsigned long) &IDTVEC(int0x80_syscall)},
          {  0, 0,           0, 0 }
  };
  
  /* Perform a multicall and check that individual calls succeeded. */
  int
  HYPERVISOR_multicall(struct multicall_entry * call_list, int nr_calls)
  {
          int ret = 0;
          int i;
  
          /* Perform the multicall. */
          PANIC_IF(_HYPERVISOR_multicall(call_list, nr_calls));
  
          /* Check the results of individual hypercalls. */
          for (i = 0; i < nr_calls; i++)
                  if (unlikely(call_list[i].result < 0))
                          ret++;
          if (unlikely(ret > 0))
                  panic("%d multicall(s) failed: cpu %d\n",
                      ret, smp_processor_id());
  
          /* If we didn't panic already, everything succeeded. */
          return (0);
  }
  
  /********** CODE WORTH KEEPING ABOVE HERE *****************/ 
  
  void xen_failsafe_handler(void);
  
  void
  xen_failsafe_handler(void)
  {
  
          panic("xen_failsafe_handler called!\n");
  }
  
  void xen_handle_thread_switch(struct pcb *pcb);
  
  /* This is called by cpu_switch() when switching threads. */
  /* The pcb arg refers to the process control block of the */
  /* next thread which is to run */
  void
  xen_handle_thread_switch(struct pcb *pcb)
  {
      uint32_t *a = (uint32_t *)&PCPU_GET(fsgs_gdt)[0];
      uint32_t *b = (uint32_t *)&pcb->pcb_fsd;
      multicall_entry_t mcl[3];
      int i = 0;
  
      /* Notify Xen of task switch */
      mcl[i].op = __HYPERVISOR_stack_switch;
      mcl[i].args[0] = GSEL(GDATA_SEL, SEL_KPL);
      mcl[i++].args[1] = (unsigned long)pcb;
  
      /* Check for update of fsd */
      if (*a != *b || *(a+1) != *(b+1)) {
          mcl[i].op = __HYPERVISOR_update_descriptor;
          *(uint64_t *)&mcl[i].args[0] = vtomach((vm_offset_t)a);
          *(uint64_t *)&mcl[i++].args[2] = *(uint64_t *)b;
      }    
  
      a += 2;
      b += 2;
  
      /* Check for update of gsd */
      if (*a != *b || *(a+1) != *(b+1)) {
          mcl[i].op = __HYPERVISOR_update_descriptor;
          *(uint64_t *)&mcl[i].args[0] = vtomach((vm_offset_t)a);
          *(uint64_t *)&mcl[i++].args[2] = *(uint64_t *)b;
      }    
  
      (void)HYPERVISOR_multicall(mcl, i);
  }

Cache object: bc671559f7ebe8d77889248fc69ff113