remove xhat
The xhat infrastructure was added to support hardware such as the zulu
graphics card - hardware which had on-board MMUs.  The VM used the xhat code
to keep the CPU's and Zulu's page tables in-sync.  Since the only xhat user
was zulu (which is gone), we can safely remove it simplifying the whole VM
subsystem.
Assorted notes:
- AS_BUSY flag was used solely by xhat

          --- old/usr/src/uts/common/vm/vm_rm.c
          +++ new/usr/src/uts/common/vm/vm_rm.c

   1    1  /*
   2    2   * CDDL HEADER START
   3    3   *
   4    4   * The contents of this file are subject to the terms of the
   5    5   * Common Development and Distribution License (the "License").
   6    6   * You may not use this file except in compliance with the License.
   7    7   *
   8    8   * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9    9   * or http://www.opensolaris.org/os/licensing.
  10   10   * See the License for the specific language governing permissions
  11   11   * and limitations under the License.
  12   12   *
  13   13   * When distributing Covered Code, include this CDDL HEADER in each
  14   14   * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15   15   * If applicable, add the following below this CDDL HEADER, with the
  16   16   * fields enclosed by brackets "[]" replaced with your own identifying
  17   17   * information: Portions Copyright [yyyy] [name of copyright owner]
  18   18   *
  19   19   * CDDL HEADER END
  20   20   */
  21   21  /*
  22   22   * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  23   23   * Use is subject to license terms.
  24   24   */
  25   25  
  26   26  /*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
  27   27  /*        All Rights Reserved   */
  28   28  
  29   29  /*
  30   30   * University Copyright- Copyright (c) 1982, 1986, 1988
  31   31   * The Regents of the University of California
  32   32   * All Rights Reserved
  33   33   *
  34   34   * University Acknowledgment- Portions of this document are derived from
  35   35   * software developed by the University of California, Berkeley, and its
  36   36   * contributors.
  37   37   */
  38   38  
  39   39  #include <sys/types.h>
  40   40  #include <sys/t_lock.h>
  41   41  #include <sys/param.h>
  42   42  #include <sys/systm.h>
  43   43  #include <sys/mman.h>
  44   44  #include <sys/sysmacros.h>
  45   45  #include <sys/errno.h>
  46   46  #include <sys/signal.h>
  47   47  #include <sys/user.h>
  48   48  #include <sys/proc.h>
  49   49  #include <sys/cmn_err.h>
  50   50  #include <sys/debug.h>
  51   51  
  52   52  #include <vm/hat.h>
  53   53  #include <vm/as.h>
  54   54  #include <vm/seg_vn.h>
  55   55  #include <vm/rm.h>
  56   56  #include <vm/seg.h>
  57   57  #include <vm/page.h>

  58   58  
  59   59  /*
  60   60   * Yield the memory claim requirement for an address space.
  61   61   *
  62   62   * This is currently implemented as the number of active hardware
  63   63   * translations that have page structures.  Therefore, it can
  64   64   * underestimate the traditional resident set size, eg, if the
  65   65   * physical page is present and the hardware translation is missing;
  66   66   * and it can overestimate the rss, eg, if there are active
  67   67   * translations to a frame buffer with page structs.
  68      - * Also, it does not take sharing and XHATs into account.
       68 + * Also, it does not take sharing into account.
  69   69   */
  70   70  size_t
  71   71  rm_asrss(as)
  72   72          register struct as *as;
  73   73  {
  74   74          if (as != (struct as *)NULL && as != &kas)
  75   75                  return ((size_t)btop(hat_get_mapped_size(as->a_hat)));
  76   76          else
  77   77                  return (0);
  78   78  }

  79   79  
  80   80  /*
  81   81   * Return a 16-bit binary fraction representing the percent of total memory
  82   82   * used by this address space.  Binary point is to right of high-order bit.
  83   83   * Defined as the ratio of a_rss for the process to total physical memory.
  84   84   * This assumes 2s-complement arithmetic and that shorts and longs are
  85   85   * 16 bits and 32 bits, respectively.
  86   86   */
  87   87  ushort_t
  88   88  rm_pctmemory(struct as *as)
  89   89  {
  90   90          /* This can't overflow */
  91   91          ulong_t num = (ulong_t)rm_asrss(as) << (PAGESHIFT-1);
  92   92          int shift = 16 - PAGESHIFT;
  93   93          ulong_t total = total_pages;
  94   94  
  95   95          if (shift < 0) {
  96   96                  num >>= (-shift);
  97   97                  shift = 0;
  98   98          }
  99   99          while (shift > 0 && (num & 0x80000000) == 0) {
 100  100                  shift--;
 101  101                  num <<= 1;
 102  102          }
 103  103          if (shift > 0)
 104  104                  total >>= shift;
 105  105  
 106  106          return (num / total);
 107  107  }

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