xnu-517.tar.gz

[apple/xnu.git] / osfmk / ppc / pcb.c

/*
 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/*
 * @OSF_COPYRIGHT@
 */
/* 
 * Copyright (c) 1990,1991,1992 The University of Utah and
 * the Center for Software Science (CSS).  All rights reserved.
 *
 * Permission to use, copy, modify and distribute this software is hereby
 * granted provided that (1) source code retains these copyright, permission,
 * and disclaimer notices, and (2) redistributions including binaries
 * reproduce the notices in supporting documentation, and (3) all advertising
 * materials mentioning features or use of this software display the following
 * acknowledgement: ``This product includes software developed by the Center
 * for Software Science at the University of Utah.''
 *
 * THE UNIVERSITY OF UTAH AND CSS ALLOW FREE USE OF THIS SOFTWARE IN ITS "AS
 * IS" CONDITION.  THE UNIVERSITY OF UTAH AND CSS DISCLAIM ANY LIABILITY OF
 * ANY KIND FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 *
 * CSS requests users of this software to return to css-dist@cs.utah.edu any
 * improvements that they make and grant CSS redistribution rights.
 *
 *      Utah $Hdr: pcb.c 1.23 92/06/27$
 */

#include <cpus.h>
#include <debug.h>

#include <types.h>
#include <kern/task.h>
#include <kern/thread.h>
#include <kern/thread_act.h>
#include <kern/thread_swap.h>
#include <mach/thread_status.h>
#include <vm/vm_kern.h>
#include <kern/mach_param.h>

#include <kern/misc_protos.h>
#include <ppc/misc_protos.h>
#include <ppc/exception.h>
#include <ppc/proc_reg.h>
#include <kern/spl.h>
#include <ppc/pmap.h>
#include <ppc/trap.h>
#include <ppc/mappings.h>
#include <ppc/savearea.h>
#include <ppc/Firmware.h>
#include <ppc/asm.h>
#include <ppc/thread_act.h>
#include <ppc/vmachmon.h>
#include <ppc/low_trace.h>

#include <sys/kdebug.h>

extern int              real_ncpus;                                             /* Number of actual CPUs */
extern struct   Saveanchor saveanchor;                  /* Aliged savearea anchor */

void    machine_act_terminate(thread_act_t      act);

/*
 * These constants are dumb. They should not be in asm.h!
 */

#define KF_SIZE         (FM_SIZE+ARG_SIZE+FM_REDZONE)

#if DEBUG
int   fpu_trap_count = 0;
int   fpu_switch_count = 0;
int   vec_trap_count = 0;
int   vec_switch_count = 0;
#endif

/*
 * consider_machine_collect: try to collect machine-dependent pages
 */
void
consider_machine_collect()
{
    /*
     * none currently available
     */
        return;
}

void
consider_machine_adjust()
{
        consider_mapping_adjust();
}

/*
 * switch_context: Switch from one thread to another, needed for
 *                 switching of space
 * 
 */
thread_t
machine_switch_context(
        thread_t                        old,
        thread_continue_t       continuation,
        thread_t                        new)
{
        register thread_act_t old_act = old->top_act, new_act = new->top_act;
        register thread_t retval;
        pmap_t  new_pmap;
        facility_context *fowner;
        struct per_proc_info *ppinfo;

        if (old == new)
                panic("machine_switch_context");

        ppinfo = getPerProc();                                                          /* Get our processor block */

        ppinfo->old_thread = (unsigned int)old;
        ppinfo->cpu_flags &= ~traceBE;                                           /* disable branch tracing if on */
               
        check_simple_locks();

        /* Our context might wake up on another processor, so we must
         * not keep hot state in our FPU, it must go back to the pcb
         * so that it can be found by the other if needed
         */
        if(real_ncpus > 1) {                                                            /* This is potentially slow, so only do when actually SMP */
                fowner = ppinfo->FPU_owner;                                             /* Cache this because it may change */
                if(fowner) {                                                                    /* Is there any live context? */
                        if(fowner->facAct == old->top_act) {            /* Is it for us? */
                                fpu_save(fowner);                                               /* Yes, save it */
                        }
                }
                fowner = ppinfo->VMX_owner;                                             /* Cache this because it may change */
                if(fowner) {                                                                    /* Is there any live context? */
                        if(fowner->facAct == old->top_act) {            /* Is it for us? */
                                vec_save(fowner);                                               /* Yes, save it */
                        }
                }
        }

        /*
         * If old thread is running VM, save per proc userProtKey and FamVMmode spcFlags bits in the thread spcFlags
         * This bits can be modified in the per proc without updating the thread spcFlags
         */
        if(old_act->mact.specFlags & runningVM) {
                old_act->mact.specFlags &=  ~(userProtKey|FamVMmode);
                old_act->mact.specFlags |= (ppinfo->spcFlags) & (userProtKey|FamVMmode);
        }

        /*
         * We do not have to worry about the PMAP module, so switch.
         *
         * We must not use top_act->map since this may not be the actual
         * task map, but the map being used for a klcopyin/out.
         */

        if(new_act->mact.specFlags & runningVM) {                       /* Is the new guy running a VM? */
                pmap_switch(new_act->mact.vmmCEntry->vmmPmap);  /* Switch to the VM's pmap */
                ppinfo->VMMareaPhys = new_act->mact.vmmCEntry->vmmContextPhys;
                ppinfo->VMMXAFlgs = new_act->mact.vmmCEntry->vmmXAFlgs;
                ppinfo->FAMintercept = new_act->mact.vmmCEntry->vmmFAMintercept;
        }
        else {                                                                                          /* otherwise, we use the task's pmap */
                new_pmap = new_act->task->map->pmap;
                if ((old_act->task->map->pmap != new_pmap) || (old_act->mact.specFlags & runningVM)) {
                        pmap_switch(new_pmap);                                          /* Switch if there is a change */
                }
        }

        if(old_act->mact.cioSpace != invalSpace) {                      /* Does our old guy have an active copyin/out? */
                old_act->mact.cioSpace |= cioSwitchAway;                /* Show we switched away from this guy */
                hw_blow_seg(copyIOaddr);                                                /* Blow off the first segment */
                hw_blow_seg(copyIOaddr + 0x10000000ULL);                /* Blow off the second segment */
        }

        KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SCHED,MACH_SCHED) | DBG_FUNC_NONE,
                     old->reason, (int)new, old->sched_pri, new->sched_pri, 0);

        retval = Switch_context(old, continuation, new);
        assert(retval != (struct thread_shuttle*)NULL);

        if (branch_tracing_enabled()) {
                ppinfo = getPerProc();                                                  /* Get our processor block */
                ppinfo->cpu_flags |= traceBE;                                   /* restore branch tracing */
        }

        /* We've returned from having switched context, so we should be
         * back in the original context.
         */

        return retval;
}

/*
 * Initialize the machine-dependent state for a new thread.
 */
kern_return_t
machine_thread_create(
        thread_t                thread,
        task_t                  task)
{
        savearea                *sv;                                                                    /* Pointer to newly allocated savearea */
        unsigned int    *CIsTooLimited, i;

        hw_atomic_add((uint32_t *)&saveanchor.savetarget, 4);   /* Account for the number of saveareas we think we "need"
                                                                                                                           for this activation */
        assert(thread->mact.pcb == (savearea *)0);                              /* Make sure there was no previous savearea */
        
        sv = save_alloc();                                                                              /* Go get us a savearea */
                
        bzero((char *)((unsigned int)sv + sizeof(savearea_comm)), (sizeof(savearea) - sizeof(savearea_comm)));  /* Clear it */
                
        sv->save_hdr.save_prev = 0;                                                             /* Clear the back pointer */
        sv->save_hdr.save_flags = (sv->save_hdr.save_flags & ~SAVtype) | (SAVgeneral << SAVtypeshft);   /* Mark as in use */
        sv->save_hdr.save_act = (struct thread_activation *)thread;     /* Set who owns it */
        thread->mact.pcb = sv;                                                                  /* Point to the save area */
        thread->mact.curctx = &thread->mact.facctx;                             /* Initialize facility context */
        thread->mact.facctx.facAct = thread;                                    /* Initialize facility context pointer to activation */
        thread->mact.cioSpace = invalSpace;                                             /* Initialize copyin/out space to invalid */
        thread->mact.preemption_count = 0;                                              /* Initialize preemption counter */

        /*
         * User threads will pull their context from the pcb when first
         * returning to user mode, so fill in all the necessary values.
         * Kernel threads are initialized from the save state structure 
         * at the base of the kernel stack (see stack_attach()).
         */

        thread->mact.upcb = sv;                                                                 /* Set user pcb */
        sv->save_srr1 = (uint64_t)MSR_EXPORT_MASK_SET;                  /* Set the default user MSR */
        sv->save_fpscr = 0;                                                                             /* Clear all floating point exceptions */
        sv->save_vrsave = 0;                                                                    /* Set the vector save state */
        sv->save_vscr[0] = 0x00000000;                                  
        sv->save_vscr[1] = 0x00000000;                                  
        sv->save_vscr[2] = 0x00000000;                                  
        sv->save_vscr[3] = 0x00010000;                                                  /* Disable java mode and clear saturated */
        
    return(KERN_SUCCESS);
}

/*
 * Machine-dependent cleanup prior to destroying a thread
 */
void
machine_thread_destroy(
        thread_t                thread)
{
        register savearea *pcb, *ppsv;
        register savearea_vec *vsv, *vpsv;
        register savearea_fpu *fsv, *fpsv;
        register savearea *svp;
        register int i;

/*
 *      This function will release all context.
 */

        machine_act_terminate(thread);                                                  /* Make sure all virtual machines are dead first */
 
/*
 *
 *      Walk through and release all floating point and vector contexts. Also kill live context.
 *
 */
 
        toss_live_vec(thread->mact.curctx);                                             /* Dump live vectors */

        vsv = thread->mact.curctx->VMXsave;                                             /* Get the top vector savearea */
        
        while(vsv) {                                                                                    /* Any VMX saved state? */
                vpsv = vsv;                                                                                     /* Remember so we can toss this */
                vsv = CAST_DOWN(savearea_vec *, vsv->save_hdr.save_prev);  /* Get one underneath our's */
                save_release((savearea *)vpsv);                                         /* Release it */
        }
        
        thread->mact.curctx->VMXsave = 0;                                                       /* Kill chain */
 
        toss_live_fpu(thread->mact.curctx);                                             /* Dump live float */

        fsv = thread->mact.curctx->FPUsave;                                             /* Get the top float savearea */
        
        while(fsv) {                                                                                    /* Any float saved state? */
                fpsv = fsv;                                                                                     /* Remember so we can toss this */
                fsv = CAST_DOWN(savearea_fpu *, fsv->save_hdr.save_prev);   /* Get one underneath our's */
                save_release((savearea *)fpsv);                                         /* Release it */
        }
        
        thread->mact.curctx->FPUsave = 0;                                                       /* Kill chain */

/*
 * free all regular saveareas.
 */

        pcb = thread->mact.pcb;                                                                 /* Get the general savearea */
        
        while(pcb) {                                                                                    /* Any float saved state? */
                ppsv = pcb;                                                                                     /* Remember so we can toss this */
                pcb = CAST_DOWN(savearea *, pcb->save_hdr.save_prev);  /* Get one underneath our's */ 
                save_release(ppsv);                                                                     /* Release it */
        }
        
        hw_atomic_sub((uint32_t *)&saveanchor.savetarget, 4);   /* Unaccount for the number of saveareas we think we "need" */
}

/*
 * Number of times we needed to swap an activation back in before
 * switching to it.
 */
int switch_act_swapins = 0;

/*
 * machine_switch_act
 *
 * Machine-dependent details of activation switching.  Called with
 * RPC locks held and preemption disabled.
 */
void
machine_switch_act( 
        thread_t                thread,
        thread_act_t    old,
        thread_act_t    new)
{
        pmap_t          new_pmap;
        facility_context *fowner;
        struct per_proc_info *ppinfo;
        
        ppinfo = getPerProc();                                                          /* Get our processor block */

        /* Our context might wake up on another processor, so we must
         * not keep hot state in our FPU, it must go back to the pcb
         * so that it can be found by the other if needed
         */
        if(real_ncpus > 1) {                                                            /* This is potentially slow, so only do when actually SMP */
                fowner = ppinfo->FPU_owner;                                             /* Cache this because it may change */
                if(fowner) {                                                                    /* Is there any live context? */
                        if(fowner->facAct == old) {                                     /* Is it for us? */
                                fpu_save(fowner);                                               /* Yes, save it */
                        }
                }
                fowner = ppinfo->VMX_owner;                                             /* Cache this because it may change */
                if(fowner) {                                                                    /* Is there any live context? */
                        if(fowner->facAct == old) {                                     /* Is it for us? */
                                vec_save(fowner);                                               /* Yes, save it */
                        }
                }
        }

        old->mact.cioSpace |= cioSwitchAway;                            /* Show we switched away from this guy */

        ast_context(new, cpu_number());

        /* Activations might have different pmaps 
         * (process->kernel->server, for example).
         * Change space if needed
         */

        if(new->mact.specFlags & runningVM) {                   /* Is the new guy running a VM? */
                pmap_switch(new->mact.vmmCEntry->vmmPmap);      /* Switch to the VM's pmap */
        }
        else {                                                                                          /* otherwise, we use the task's pmap */
                new_pmap = new->task->map->pmap;
                if ((old->task->map->pmap != new_pmap)  || (old->mact.specFlags & runningVM)) {
                        pmap_switch(new_pmap);
                }
        }

}

/*
 * act_machine_sv_free
 * release saveareas associated with an act. if flag is true, release
 * user level savearea(s) too, else don't
 *
 * this code cannot block so we call the proper save area free routine
 */
void
act_machine_sv_free(thread_act_t act)
{
        register savearea *pcb, *userpcb;
        register savearea_vec *vsv, *vpst, *vsvt;
        register savearea_fpu *fsv, *fpst, *fsvt;
        register savearea *svp;
        register int i;

/*
 *      This function will release all non-user state context.
 */
 
/*
 *
 *      Walk through and release all floating point and vector contexts that are not
 *      user state.  We will also blow away live context if it belongs to non-user state.
 *      Note that the level can not change while we are in this code.  Nor can another
 *      context be pushed on the stack.
 *
 *      We do nothing here if the current level is user.  Otherwise,
 *      the live context is cleared.  Then we find the user saved context.
 *      Next,  we take the sync lock (to keep us from munging things in *_switch).
 *      The level is set to 0 and all stacked context other than user is dequeued.
 *      Then we unlock.  Next, all of the old kernel contexts are released.
 *
 */
 
        if(act->mact.curctx->VMXlevel) {                                                /* Is the current level user state? */
                
                toss_live_vec(act->mact.curctx);                                        /* Dump live vectors if is not user */

                vsv = act->mact.curctx->VMXsave;                                        /* Get the top vector savearea */
                
                while(vsv && vsv->save_hdr.save_level) vsv = (savearea_vec *)vsv->save_hdr.save_prev;   /* Find user context if any */
        
                if(!hw_lock_to((hw_lock_t)&act->mact.curctx->VMXsync, LockTimeOut)) {   /* Get the sync lock */ 
                        panic("act_machine_sv_free - timeout getting VMX sync lock\n"); /* Tell all and die */
                }
                
                vsvt = act->mact.curctx->VMXsave;                                       /* Get the top of the chain */
                act->mact.curctx->VMXsave = vsv;                                        /* Point to the user context */
                act->mact.curctx->VMXlevel = 0;                                         /* Set the level to user */
                hw_lock_unlock((hw_lock_t)&act->mact.curctx->VMXsync);  /* Unlock */
                
                while(vsvt) {                                                                           /* Clear any VMX saved state */
                        if (vsvt == vsv) break;                                                 /* Done when hit user if any */
                        vpst = vsvt;                                                                    /* Remember so we can toss this */
                        vsvt = (savearea_vec *)vsvt->save_hdr.save_prev;        /* Get one underneath our's */          
                        save_ret((savearea *)vpst);                                             /* Release it */
                }
                
        }
 
        if(act->mact.curctx->FPUlevel) {                                                /* Is the current level user state? */
                
                toss_live_fpu(act->mact.curctx);                                        /* Dump live floats if is not user */

                fsv = act->mact.curctx->FPUsave;                                        /* Get the top floats savearea */
                
                while(fsv && fsv->save_hdr.save_level) fsv = (savearea_fpu *)fsv->save_hdr.save_prev;   /* Find user context if any */
        
                if(!hw_lock_to((hw_lock_t)&act->mact.curctx->FPUsync, LockTimeOut)) {   /* Get the sync lock */ 
                        panic("act_machine_sv_free - timeout getting FPU sync lock\n"); /* Tell all and die */
                }
                
                fsvt = act->mact.curctx->FPUsave;                                       /* Get the top of the chain */
                act->mact.curctx->FPUsave = fsv;                                        /* Point to the user context */
                act->mact.curctx->FPUlevel = 0;                                         /* Set the level to user */
                hw_lock_unlock((hw_lock_t)&act->mact.curctx->FPUsync);  /* Unlock */
                
                while(fsvt) {                                                                           /* Clear any VMX saved state */
                        if (fsvt == fsv) break;                                                 /* Done when hit user if any */
                        fpst = fsvt;                                                                    /* Remember so we can toss this */
                        fsvt = (savearea_fpu *)fsvt->save_hdr.save_prev;        /* Get one underneath our's */          
                        save_ret((savearea *)fpst);                                             /* Release it */
                }
                
        }

/*
 * free all regular saveareas except a user savearea, if any
 */

        pcb = act->mact.pcb;                                                                    /* Get the general savearea */
        userpcb = 0;                                                                                    /* Assume no user context for now */
        
        while(pcb) {                                                                                    /* Any float saved state? */
                if (pcb->save_srr1 & MASK(MSR_PR)) {                            /* Is this a user savearea? */
                        userpcb = pcb;                                                                  /* Remember so we can toss this */
                        break;
                }
                svp = pcb;                                                                                      /* Remember this */
                pcb = CAST_DOWN(savearea *, pcb->save_hdr.save_prev);  /* Get one underneath our's */ 
                save_ret(svp);                                                                          /* Release it */
        }
        
        act->mact.pcb = userpcb;                                                                /* Chain in the user if there is one, or 0 if not */
        
}

void
machine_thread_set_current(thread_t     thread)
{
    set_machine_current_act(thread->top_act);
}

void
machine_act_terminate(
        thread_act_t    act)
{
        if(act->mact.bbDescAddr) {                                                              /* Check if the Blue box assist is active */
                disable_bluebox_internal(act);                                          /* Kill off bluebox */
        }
        
        if(act->mact.vmmControl) {                                                              /* Check if VMM is active */
                vmm_tear_down_all(act);                                                         /* Kill off all VMM contexts */
        }
}

void
machine_thread_terminate_self(void)
{
        machine_act_terminate(current_act());
}

void
machine_thread_init(void)
{
#ifdef  MACHINE_STACK
#if KERNEL_STACK_SIZE > PPC_PGBYTES
        panic("KERNEL_STACK_SIZE can't be greater than PPC_PGBYTES\n");
#endif
#endif
}

#if MACH_ASSERT

void
dump_thread(thread_t th)
{
        printf(" thread @ 0x%x:\n", th);
}

int
    dump_act(thread_act_t thr_act)
{
    if (!thr_act)
        return(0);

    printf("thr_act(0x%x)(%d): thread=%x(%d) task=%x(%d)\n",
           thr_act, thr_act->ref_count,
           thr_act->thread, thr_act->thread ? thr_act->thread->ref_count:0,
           thr_act->task,   thr_act->task   ? thr_act->task->ref_count : 0);

    printf("\tsusp=%x active=%x hi=%x lo=%x\n",
           0 /*thr_act->alerts*/, 0 /*thr_act->alert_mask*/,
           thr_act->suspend_count, thr_act->active,
           thr_act->higher, thr_act->lower);

    return((int)thr_act);
}

#endif

unsigned int 
get_useraddr()
{
        return(current_act()->mact.upcb->save_srr0);
}

/*
 * detach and return a kernel stack from a thread
 */

vm_offset_t
machine_stack_detach(
        thread_t                thread)
{
  vm_offset_t stack;

  KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_SCHED,MACH_STACK_DETACH),
                                                                                        thread, thread->priority,
                                                                                        thread->sched_pri, 0, 0);

  if (thread->top_act)
          act_machine_sv_free(thread->top_act);

  stack = thread->kernel_stack;
  thread->kernel_stack = 0;
  return(stack);
}

/*
 * attach a kernel stack to a thread and initialize it
 *
 * attaches a stack to a thread. if there is no save
 * area we allocate one.  the top save area is then
 * loaded with the pc (continuation address), the initial
 * stack pointer, and a std kernel MSR. if the top
 * save area is the user save area bad things will 
 * happen
 *
 */

void
machine_stack_attach(
        thread_t                thread,
        vm_offset_t             stack,
        void                     (*start)(thread_t))
{
  thread_act_t thr_act;
  unsigned int *kss;
  struct savearea *sv;

        KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_SCHED,MACH_STACK_ATTACH),
            thread, thread->priority,
            thread->sched_pri, start,
            0);

  assert(stack);
  kss = (unsigned int *)STACK_IKS(stack);
  thread->kernel_stack = stack;

  /* during initialization we sometimes do not have an
     activation. in that case do not do anything */
  if ((thr_act = thread->top_act) != 0) {
    sv = save_get();  /* cannot block */
        sv->save_hdr.save_flags = (sv->save_hdr.save_flags & ~SAVtype) | (SAVgeneral << SAVtypeshft);   /* Mark as in use */
    sv->save_hdr.save_act = (struct thread_activation *)thr_act;
        sv->save_hdr.save_prev = (addr64_t)((uintptr_t)thr_act->mact.pcb);
    thr_act->mact.pcb = sv;

    sv->save_srr0 = (unsigned int) start;
    /* sv->save_r3 = ARG ? */
    sv->save_r1 = (vm_offset_t)((int)kss - KF_SIZE);
        sv->save_srr1 = MSR_SUPERVISOR_INT_OFF;
        sv->save_fpscr = 0;                                                                     /* Clear all floating point exceptions */
        sv->save_vrsave = 0;                                                            /* Set the vector save state */
        sv->save_vscr[3] = 0x00010000;                                          /* Supress java mode */
    *(CAST_DOWN(int *, sv->save_r1)) = 0;
    thr_act->mact.ksp = 0;                            
  }

  return;
}

/*
 * move a stack from old to new thread
 */

void
machine_stack_handoff(
        thread_t                old,
        thread_t                new)
{

        vm_offset_t stack;
        pmap_t new_pmap;
        facility_context *fowner;
        mapping *mp;
        struct per_proc_info *ppinfo;
        
        assert(new->top_act);
        assert(old->top_act);

        if (old == new)
                panic("machine_stack_handoff");
        
        stack = machine_stack_detach(old);
        new->kernel_stack = stack;
        if (stack == old->reserved_stack) {
                assert(new->reserved_stack);
                old->reserved_stack = new->reserved_stack;
                new->reserved_stack = stack;
        }

        ppinfo = getPerProc();                                                          /* Get our processor block */

        ppinfo->cpu_flags &= ~traceBE;                                          /* Turn off special branch trace */

        if(real_ncpus > 1) {                                                            /* This is potentially slow, so only do when actually SMP */
                fowner = ppinfo->FPU_owner;                                             /* Cache this because it may change */
                if(fowner) {                                                                    /* Is there any live context? */
                        if(fowner->facAct == old->top_act) {            /* Is it for us? */
                                fpu_save(fowner);                                               /* Yes, save it */
                        }
                }
                fowner = ppinfo->VMX_owner;                                             /* Cache this because it may change */
                if(fowner) {                                                                    /* Is there any live context? */
                        if(fowner->facAct == old->top_act) {            /* Is it for us? */
                                vec_save(fowner);                                               /* Yes, save it */
                        }
                }
        }

        /*
         * If old thread is running VM, save per proc userProtKey and FamVMmode spcFlags bits in the thread spcFlags
         * This bits can be modified in the per proc without updating the thread spcFlags
         */
        if(old->top_act->mact.specFlags & runningVM) {                  /* Is the current thread running a VM? */
                old->top_act->mact.specFlags &= ~(userProtKey|FamVMmode);
                old->top_act->mact.specFlags |= (ppinfo->spcFlags) & (userProtKey|FamVMmode);
        }

        KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SCHED,MACH_STACK_HANDOFF) | DBG_FUNC_NONE,
                     old->reason, (int)new, old->sched_pri, new->sched_pri, 0);


        if(new->top_act->mact.specFlags & runningVM) {  /* Is the new guy running a VM? */
                pmap_switch(new->top_act->mact.vmmCEntry->vmmPmap);     /* Switch to the VM's pmap */
                ppinfo->VMMareaPhys = new->top_act->mact.vmmCEntry->vmmContextPhys;
                ppinfo->VMMXAFlgs = new->top_act->mact.vmmCEntry->vmmXAFlgs;
                ppinfo->FAMintercept = new->top_act->mact.vmmCEntry->vmmFAMintercept;
        }
        else {                                                                                  /* otherwise, we use the task's pmap */
                new_pmap = new->top_act->task->map->pmap;
                if ((old->top_act->task->map->pmap != new_pmap) || (old->top_act->mact.specFlags & runningVM)) {
                        pmap_switch(new_pmap);
                }
        }

        machine_thread_set_current(new);
        ppinfo->Uassist = new->top_act->mact.cthread_self;

        ppinfo->ppbbTaskEnv = new->top_act->mact.bbTaskEnv;
        ppinfo->spcFlags = new->top_act->mact.specFlags;
        
        old->top_act->mact.cioSpace |= cioSwitchAway;   /* Show we switched away from this guy */
        mp = (mapping *)&ppinfo->ppCIOmp;
        mp->mpSpace = invalSpace;                                               /* Since we can't handoff in the middle of copy in/out, just invalidate */

        if (branch_tracing_enabled()) 
                ppinfo->cpu_flags |= traceBE;
    
        if(trcWork.traceMask) dbgTrace(0x12345678, (unsigned int)old->top_act, (unsigned int)new->top_act, 0);  /* Cut trace entry if tracing */    
    
  return;
}

/*
 * clean and initialize the current kernel stack and go to
 * the given continuation routine
 */

void
call_continuation(void (*continuation)(void) )
{

  unsigned int *kss;
  vm_offset_t tsp;

  assert(current_thread()->kernel_stack);
  kss = (unsigned int *)STACK_IKS(current_thread()->kernel_stack);
  assert(continuation);

  tsp = (vm_offset_t)((int)kss - KF_SIZE);
  assert(tsp);
  *((int *)tsp) = 0;

  Call_continuation(continuation, tsp);
  
  return;
}