target/nios2/mmu.c - qemu - Git at Google

 /*
  * Altera Nios II MMU emulation for qemu.
  *
  * Copyright (C) 2012 Chris Wulff <crwulff@gmail.com>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with this library; if not, see
  * <http://www.gnu.org/licenses/lgpl-2.1.html>
  */

 #include "qemu/osdep.h"
 #include "qemu-common.h"
 #include "cpu.h"
 #include "exec/exec-all.h"
 #include "mmu.h"

 #if !defined(CONFIG_USER_ONLY)

 /* Define this to enable MMU debug messages */
 /* #define DEBUG_MMU */

 #ifdef DEBUG_MMU
 #define MMU_LOG(x) x
 #else
 #define MMU_LOG(x)
 #endif

 void tlb_fill(CPUState *cs, target_ulong addr, MMUAccessType access_type,
               int mmu_idx, uintptr_t retaddr)
 {
     int ret;

     ret = nios2_cpu_handle_mmu_fault(cs, addr, access_type, mmu_idx);
     if (unlikely(ret)) {
         if (retaddr) {
             /* now we have a real cpu fault */
             cpu_restore_state(cs, retaddr);
         }
         cpu_loop_exit(cs);
     }
 }

 void mmu_read_debug(CPUNios2State *env, uint32_t rn)
 {
     switch (rn) {
     case CR_TLBACC:
         MMU_LOG(qemu_log("TLBACC READ %08X\n", env->regs[rn]));
         break;

     case CR_TLBMISC:
         MMU_LOG(qemu_log("TLBMISC READ %08X\n", env->regs[rn]));
         break;

     case CR_PTEADDR:
         MMU_LOG(qemu_log("PTEADDR READ %08X\n", env->regs[rn]));
         break;

     default:
         break;
     }
 }

 /* rw - 0 = read, 1 = write, 2 = fetch.  */
 unsigned int mmu_translate(CPUNios2State *env,
                            Nios2MMULookup *lu,
                            target_ulong vaddr, int rw, int mmu_idx)
 {
     Nios2CPU *cpu = nios2_env_get_cpu(env);
     int pid = (env->mmu.tlbmisc_wr & CR_TLBMISC_PID_MASK) >> 4;
     int vpn = vaddr >> 12;

     MMU_LOG(qemu_log("mmu_translate vaddr %08X, pid %08X, vpn %08X\n",
                      vaddr, pid, vpn));

     int way;
     for (way = 0; way < cpu->tlb_num_ways; way++) {

         Nios2TLBEntry *entry =
             &env->mmu.tlb[(way * cpu->tlb_num_ways) +
                           (vpn & env->mmu.tlb_entry_mask)];

         MMU_LOG(qemu_log("TLB[%d] TAG %08X, VPN %08X\n",
                          (way * cpu->tlb_num_ways) +
                          (vpn & env->mmu.tlb_entry_mask),
                          entry->tag, (entry->tag >> 12)));

         if (((entry->tag >> 12) != vpn) ||
             (((entry->tag & (1 << 11)) == 0) &&
             ((entry->tag & ((1 << cpu->pid_num_bits) - 1)) != pid))) {
             continue;
         }
         lu->vaddr = vaddr & TARGET_PAGE_MASK;
         lu->paddr = (entry->data & CR_TLBACC_PFN_MASK) << TARGET_PAGE_BITS;
         lu->prot = ((entry->data & CR_TLBACC_R) ? PAGE_READ : 0) |
                    ((entry->data & CR_TLBACC_W) ? PAGE_WRITE : 0) |
                    ((entry->data & CR_TLBACC_X) ? PAGE_EXEC : 0);

         MMU_LOG(qemu_log("HIT TLB[%d] %08X %08X %08X\n",
                          (way * cpu->tlb_num_ways) +
                          (vpn & env->mmu.tlb_entry_mask),
                          lu->vaddr, lu->paddr, lu->prot));
         return 1;
     }
     return 0;
 }

 static void mmu_flush_pid(CPUNios2State *env, uint32_t pid)
 {
     CPUState *cs = ENV_GET_CPU(env);
     Nios2CPU *cpu = nios2_env_get_cpu(env);
     int idx;
     MMU_LOG(qemu_log("TLB Flush PID %d\n", pid));

     for (idx = 0; idx < cpu->tlb_num_entries; idx++) {
         Nios2TLBEntry *entry = &env->mmu.tlb[idx];

         MMU_LOG(qemu_log("TLB[%d] => %08X %08X\n",
                          idx, entry->tag, entry->data));

         if ((entry->tag & (1 << 10)) && (!(entry->tag & (1 << 11))) &&
             ((entry->tag & ((1 << cpu->pid_num_bits) - 1)) == pid)) {
             uint32_t vaddr = entry->tag & TARGET_PAGE_MASK;

             MMU_LOG(qemu_log("TLB Flush Page %08X\n", vaddr));

             tlb_flush_page(cs, vaddr);
         }
     }
 }

 void mmu_write(CPUNios2State *env, uint32_t rn, uint32_t v)
 {
     CPUState *cs = ENV_GET_CPU(env);
     Nios2CPU *cpu = nios2_env_get_cpu(env);

     MMU_LOG(qemu_log("mmu_write %08X = %08X\n", rn, v));

     switch (rn) {
     case CR_TLBACC:
         MMU_LOG(qemu_log("TLBACC: IG %02X, FLAGS %c%c%c%c%c, PFN %05X\n",
                          v >> CR_TLBACC_IGN_SHIFT,
                          (v & CR_TLBACC_C) ? 'C' : '.',
                          (v & CR_TLBACC_R) ? 'R' : '.',
                          (v & CR_TLBACC_W) ? 'W' : '.',
                          (v & CR_TLBACC_X) ? 'X' : '.',
                          (v & CR_TLBACC_G) ? 'G' : '.',
                          v & CR_TLBACC_PFN_MASK));

         /* if tlbmisc.WE == 1 then trigger a TLB write on writes to TLBACC */
         if (env->regs[CR_TLBMISC] & CR_TLBMISC_WR) {
             int way = (env->regs[CR_TLBMISC] >> CR_TLBMISC_WAY_SHIFT);
             int vpn = (env->mmu.pteaddr_wr & CR_PTEADDR_VPN_MASK) >> 2;
             int pid = (env->mmu.tlbmisc_wr & CR_TLBMISC_PID_MASK) >> 4;
             int g = (v & CR_TLBACC_G) ? 1 : 0;
             int valid = ((vpn & CR_TLBACC_PFN_MASK) < 0xC0000) ? 1 : 0;
             Nios2TLBEntry *entry =
                 &env->mmu.tlb[(way * cpu->tlb_num_ways) +
                               (vpn & env->mmu.tlb_entry_mask)];
             uint32_t newTag = (vpn << 12) | (g << 11) | (valid << 10) | pid;
             uint32_t newData = v & (CR_TLBACC_C | CR_TLBACC_R | CR_TLBACC_W |
                                     CR_TLBACC_X | CR_TLBACC_PFN_MASK);

             if ((entry->tag != newTag) || (entry->data != newData)) {
                 if (entry->tag & (1 << 10)) {
                     /* Flush existing entry */
                     MMU_LOG(qemu_log("TLB Flush Page (OLD) %08X\n",
                                      entry->tag & TARGET_PAGE_MASK));
                     tlb_flush_page(cs, entry->tag & TARGET_PAGE_MASK);
                 }
                 entry->tag = newTag;
                 entry->data = newData;
                 MMU_LOG(qemu_log("TLB[%d] = %08X %08X\n",
                                  (way * cpu->tlb_num_ways) +
                                  (vpn & env->mmu.tlb_entry_mask),
                                  entry->tag, entry->data));
             }
             /* Auto-increment tlbmisc.WAY */
             env->regs[CR_TLBMISC] =
                 (env->regs[CR_TLBMISC] & ~CR_TLBMISC_WAY_MASK) |
                 (((way + 1) & (cpu->tlb_num_ways - 1)) <<
                  CR_TLBMISC_WAY_SHIFT);
         }

         /* Writes to TLBACC don't change the read-back value */
         env->mmu.tlbacc_wr = v;
         break;

     case CR_TLBMISC:
         MMU_LOG(qemu_log("TLBMISC: WAY %X, FLAGS %c%c%c%c%c%c, PID %04X\n",
                          v >> CR_TLBMISC_WAY_SHIFT,
                          (v & CR_TLBMISC_RD) ? 'R' : '.',
                          (v & CR_TLBMISC_WR) ? 'W' : '.',
                          (v & CR_TLBMISC_DBL) ? '2' : '.',
                          (v & CR_TLBMISC_BAD) ? 'B' : '.',
                          (v & CR_TLBMISC_PERM) ? 'P' : '.',
                          (v & CR_TLBMISC_D) ? 'D' : '.',
                          (v & CR_TLBMISC_PID_MASK) >> 4));

         if ((v & CR_TLBMISC_PID_MASK) !=
             (env->mmu.tlbmisc_wr & CR_TLBMISC_PID_MASK)) {
             mmu_flush_pid(env, (env->mmu.tlbmisc_wr & CR_TLBMISC_PID_MASK) >>
                                CR_TLBMISC_PID_SHIFT);
         }
         /* if tlbmisc.RD == 1 then trigger a TLB read on writes to TLBMISC */
         if (v & CR_TLBMISC_RD) {
             int way = (v >> CR_TLBMISC_WAY_SHIFT);
             int vpn = (env->mmu.pteaddr_wr & CR_PTEADDR_VPN_MASK) >> 2;
             Nios2TLBEntry *entry =
                 &env->mmu.tlb[(way * cpu->tlb_num_ways) +
                               (vpn & env->mmu.tlb_entry_mask)];

             env->regs[CR_TLBACC] &= CR_TLBACC_IGN_MASK;
             env->regs[CR_TLBACC] |= entry->data;
             env->regs[CR_TLBACC] |= (entry->tag & (1 << 11)) ? CR_TLBACC_G : 0;
             env->regs[CR_TLBMISC] =
                 (v & ~CR_TLBMISC_PID_MASK) |
                 ((entry->tag & ((1 << cpu->pid_num_bits) - 1)) <<
                  CR_TLBMISC_PID_SHIFT);
             env->regs[CR_PTEADDR] &= ~CR_PTEADDR_VPN_MASK;
             env->regs[CR_PTEADDR] |= (entry->tag >> 12) << CR_PTEADDR_VPN_SHIFT;
             MMU_LOG(qemu_log("TLB READ way %d, vpn %05X, tag %08X, data %08X, "
                              "tlbacc %08X, tlbmisc %08X, pteaddr %08X\n",
                              way, vpn, entry->tag, entry->data,
                              env->regs[CR_TLBACC], env->regs[CR_TLBMISC],
                              env->regs[CR_PTEADDR]));
         } else {
             env->regs[CR_TLBMISC] = v;
         }

         env->mmu.tlbmisc_wr = v;
         break;

     case CR_PTEADDR:
         MMU_LOG(qemu_log("PTEADDR: PTBASE %03X, VPN %05X\n",
                          v >> CR_PTEADDR_PTBASE_SHIFT,
                          (v & CR_PTEADDR_VPN_MASK) >> CR_PTEADDR_VPN_SHIFT));

         /* Writes to PTEADDR don't change the read-back VPN value */
         env->regs[CR_PTEADDR] = (v & ~CR_PTEADDR_VPN_MASK) |
                                 (env->regs[CR_PTEADDR] & CR_PTEADDR_VPN_MASK);
         env->mmu.pteaddr_wr = v;
         break;

     default:
         break;
     }
 }

 void mmu_init(CPUNios2State *env)
 {
     Nios2CPU *cpu = nios2_env_get_cpu(env);
     Nios2MMU *mmu = &env->mmu;

     MMU_LOG(qemu_log("mmu_init\n"));

     mmu->tlb_entry_mask = (cpu->tlb_num_entries / cpu->tlb_num_ways) - 1;
     mmu->tlb = g_new0(Nios2TLBEntry, cpu->tlb_num_entries);
 }

 void dump_mmu(FILE *f, fprintf_function cpu_fprintf, CPUNios2State *env)
 {
     Nios2CPU *cpu = nios2_env_get_cpu(env);
     int i;

     cpu_fprintf(f, "MMU: ways %d, entries %d, pid bits %d\n",
                 cpu->tlb_num_ways, cpu->tlb_num_entries,
                 cpu->pid_num_bits);

     for (i = 0; i < cpu->tlb_num_entries; i++) {
         Nios2TLBEntry *entry = &env->mmu.tlb[i];
         cpu_fprintf(f, "TLB[%d] = %08X %08X %c VPN %05X "
                     "PID %02X %c PFN %05X %c%c%c%c\n",
                     i, entry->tag, entry->data,
                     (entry->tag & (1 << 10)) ? 'V' : '-',
                     entry->tag >> 12,
                     entry->tag & ((1 << cpu->pid_num_bits) - 1),
                     (entry->tag & (1 << 11)) ? 'G' : '-',
                     entry->data & CR_TLBACC_PFN_MASK,
                     (entry->data & CR_TLBACC_C) ? 'C' : '-',
                     (entry->data & CR_TLBACC_R) ? 'R' : '-',
                     (entry->data & CR_TLBACC_W) ? 'W' : '-',
                     (entry->data & CR_TLBACC_X) ? 'X' : '-');
     }
 }

 #endif /* !CONFIG_USER_ONLY */
	/*
	* Altera Nios II MMU emulation for qemu.
	*
	* Copyright (C) 2012 Chris Wulff <crwulff@gmail.com>
	*
	* This library is free software; you can redistribute it and/or
	* modify it under the terms of the GNU Lesser General Public
	* License as published by the Free Software Foundation; either
	* version 2.1 of the License, or (at your option) any later version.
	*
	* This library is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* Lesser General Public License for more details.
	*
	* You should have received a copy of the GNU Lesser General Public
	* License along with this library; if not, see
	* <http://www.gnu.org/licenses/lgpl-2.1.html>
	*/

	#include "qemu/osdep.h"
	#include "qemu-common.h"
	#include "cpu.h"
	#include "exec/exec-all.h"
	#include "mmu.h"

	#if !defined(CONFIG_USER_ONLY)

	/* Define this to enable MMU debug messages */
	/* #define DEBUG_MMU */

	#ifdef DEBUG_MMU
	#define MMU_LOG(x) x
	#else
	#define MMU_LOG(x)
	#endif

	void tlb_fill(CPUState *cs, target_ulong addr, MMUAccessType access_type,
	int mmu_idx, uintptr_t retaddr)
	{
	int ret;

	ret = nios2_cpu_handle_mmu_fault(cs, addr, access_type, mmu_idx);
	if (unlikely(ret)) {
	if (retaddr) {
	/* now we have a real cpu fault */
	cpu_restore_state(cs, retaddr);
	}
	cpu_loop_exit(cs);
	}
	}

	void mmu_read_debug(CPUNios2State *env, uint32_t rn)
	{
	switch (rn) {
	case CR_TLBACC:
	MMU_LOG(qemu_log("TLBACC READ %08X\n", env->regs[rn]));
	break;

	case CR_TLBMISC:
	MMU_LOG(qemu_log("TLBMISC READ %08X\n", env->regs[rn]));
	break;

	case CR_PTEADDR:
	MMU_LOG(qemu_log("PTEADDR READ %08X\n", env->regs[rn]));
	break;

	default:
	break;
	}
	}

	/* rw - 0 = read, 1 = write, 2 = fetch. */
	unsigned int mmu_translate(CPUNios2State *env,
	Nios2MMULookup *lu,
	target_ulong vaddr, int rw, int mmu_idx)
	{
	Nios2CPU *cpu = nios2_env_get_cpu(env);
	int pid = (env->mmu.tlbmisc_wr & CR_TLBMISC_PID_MASK) >> 4;
	int vpn = vaddr >> 12;

	MMU_LOG(qemu_log("mmu_translate vaddr %08X, pid %08X, vpn %08X\n",
	vaddr, pid, vpn));

	int way;
	for (way = 0; way < cpu->tlb_num_ways; way++) {

	Nios2TLBEntry *entry =
	&env->mmu.tlb[(way * cpu->tlb_num_ways) +
	(vpn & env->mmu.tlb_entry_mask)];

	MMU_LOG(qemu_log("TLB[%d] TAG %08X, VPN %08X\n",
	(way * cpu->tlb_num_ways) +
	(vpn & env->mmu.tlb_entry_mask),
	entry->tag, (entry->tag >> 12)));

	if (((entry->tag >> 12) != vpn) \|\|
	(((entry->tag & (1 << 11)) == 0) &&
	((entry->tag & ((1 << cpu->pid_num_bits) - 1)) != pid))) {
	continue;
	}
	lu->vaddr = vaddr & TARGET_PAGE_MASK;
	lu->paddr = (entry->data & CR_TLBACC_PFN_MASK) << TARGET_PAGE_BITS;
	lu->prot = ((entry->data & CR_TLBACC_R) ? PAGE_READ : 0) \|
	((entry->data & CR_TLBACC_W) ? PAGE_WRITE : 0) \|
	((entry->data & CR_TLBACC_X) ? PAGE_EXEC : 0);

	MMU_LOG(qemu_log("HIT TLB[%d] %08X %08X %08X\n",
	(way * cpu->tlb_num_ways) +
	(vpn & env->mmu.tlb_entry_mask),
	lu->vaddr, lu->paddr, lu->prot));
	return 1;
	}
	return 0;
	}

	static void mmu_flush_pid(CPUNios2State *env, uint32_t pid)
	{
	CPUState *cs = ENV_GET_CPU(env);
	Nios2CPU *cpu = nios2_env_get_cpu(env);
	int idx;
	MMU_LOG(qemu_log("TLB Flush PID %d\n", pid));

	for (idx = 0; idx < cpu->tlb_num_entries; idx++) {
	Nios2TLBEntry *entry = &env->mmu.tlb[idx];

	MMU_LOG(qemu_log("TLB[%d] => %08X %08X\n",
	idx, entry->tag, entry->data));

	if ((entry->tag & (1 << 10)) && (!(entry->tag & (1 << 11))) &&
	((entry->tag & ((1 << cpu->pid_num_bits) - 1)) == pid)) {
	uint32_t vaddr = entry->tag & TARGET_PAGE_MASK;

	MMU_LOG(qemu_log("TLB Flush Page %08X\n", vaddr));

	tlb_flush_page(cs, vaddr);
	}
	}
	}

	void mmu_write(CPUNios2State *env, uint32_t rn, uint32_t v)
	{
	CPUState *cs = ENV_GET_CPU(env);
	Nios2CPU *cpu = nios2_env_get_cpu(env);

	MMU_LOG(qemu_log("mmu_write %08X = %08X\n", rn, v));

	switch (rn) {
	case CR_TLBACC:
	MMU_LOG(qemu_log("TLBACC: IG %02X, FLAGS %c%c%c%c%c, PFN %05X\n",
	v >> CR_TLBACC_IGN_SHIFT,
	(v & CR_TLBACC_C) ? 'C' : '.',
	(v & CR_TLBACC_R) ? 'R' : '.',
	(v & CR_TLBACC_W) ? 'W' : '.',
	(v & CR_TLBACC_X) ? 'X' : '.',
	(v & CR_TLBACC_G) ? 'G' : '.',
	v & CR_TLBACC_PFN_MASK));

	/* if tlbmisc.WE == 1 then trigger a TLB write on writes to TLBACC */
	if (env->regs[CR_TLBMISC] & CR_TLBMISC_WR) {
	int way = (env->regs[CR_TLBMISC] >> CR_TLBMISC_WAY_SHIFT);
	int vpn = (env->mmu.pteaddr_wr & CR_PTEADDR_VPN_MASK) >> 2;
	int pid = (env->mmu.tlbmisc_wr & CR_TLBMISC_PID_MASK) >> 4;
	int g = (v & CR_TLBACC_G) ? 1 : 0;
	int valid = ((vpn & CR_TLBACC_PFN_MASK) < 0xC0000) ? 1 : 0;
	Nios2TLBEntry *entry =
	&env->mmu.tlb[(way * cpu->tlb_num_ways) +
	(vpn & env->mmu.tlb_entry_mask)];
	uint32_t newTag = (vpn << 12) \| (g << 11) \| (valid << 10) \| pid;
	uint32_t newData = v & (CR_TLBACC_C \| CR_TLBACC_R \| CR_TLBACC_W \|
	CR_TLBACC_X \| CR_TLBACC_PFN_MASK);

	if ((entry->tag != newTag) \|\| (entry->data != newData)) {
	if (entry->tag & (1 << 10)) {
	/* Flush existing entry */
	MMU_LOG(qemu_log("TLB Flush Page (OLD) %08X\n",
	entry->tag & TARGET_PAGE_MASK));
	tlb_flush_page(cs, entry->tag & TARGET_PAGE_MASK);
	}
	entry->tag = newTag;
	entry->data = newData;
	MMU_LOG(qemu_log("TLB[%d] = %08X %08X\n",
	(way * cpu->tlb_num_ways) +
	(vpn & env->mmu.tlb_entry_mask),
	entry->tag, entry->data));
	}
	/* Auto-increment tlbmisc.WAY */
	env->regs[CR_TLBMISC] =
	(env->regs[CR_TLBMISC] & ~CR_TLBMISC_WAY_MASK) \|
	(((way + 1) & (cpu->tlb_num_ways - 1)) <<
	CR_TLBMISC_WAY_SHIFT);
	}

	/* Writes to TLBACC don't change the read-back value */
	env->mmu.tlbacc_wr = v;
	break;

	case CR_TLBMISC:
	MMU_LOG(qemu_log("TLBMISC: WAY %X, FLAGS %c%c%c%c%c%c, PID %04X\n",
	v >> CR_TLBMISC_WAY_SHIFT,
	(v & CR_TLBMISC_RD) ? 'R' : '.',
	(v & CR_TLBMISC_WR) ? 'W' : '.',
	(v & CR_TLBMISC_DBL) ? '2' : '.',
	(v & CR_TLBMISC_BAD) ? 'B' : '.',
	(v & CR_TLBMISC_PERM) ? 'P' : '.',
	(v & CR_TLBMISC_D) ? 'D' : '.',
	(v & CR_TLBMISC_PID_MASK) >> 4));

	if ((v & CR_TLBMISC_PID_MASK) !=
	(env->mmu.tlbmisc_wr & CR_TLBMISC_PID_MASK)) {
	mmu_flush_pid(env, (env->mmu.tlbmisc_wr & CR_TLBMISC_PID_MASK) >>
	CR_TLBMISC_PID_SHIFT);
	}
	/* if tlbmisc.RD == 1 then trigger a TLB read on writes to TLBMISC */
	if (v & CR_TLBMISC_RD) {
	int way = (v >> CR_TLBMISC_WAY_SHIFT);
	int vpn = (env->mmu.pteaddr_wr & CR_PTEADDR_VPN_MASK) >> 2;
	Nios2TLBEntry *entry =
	&env->mmu.tlb[(way * cpu->tlb_num_ways) +
	(vpn & env->mmu.tlb_entry_mask)];

	env->regs[CR_TLBACC] &= CR_TLBACC_IGN_MASK;
	env->regs[CR_TLBACC] \|= entry->data;
	env->regs[CR_TLBACC] \|= (entry->tag & (1 << 11)) ? CR_TLBACC_G : 0;
	env->regs[CR_TLBMISC] =
	(v & ~CR_TLBMISC_PID_MASK) \|
	((entry->tag & ((1 << cpu->pid_num_bits) - 1)) <<
	CR_TLBMISC_PID_SHIFT);
	env->regs[CR_PTEADDR] &= ~CR_PTEADDR_VPN_MASK;
	env->regs[CR_PTEADDR] \|= (entry->tag >> 12) << CR_PTEADDR_VPN_SHIFT;
	MMU_LOG(qemu_log("TLB READ way %d, vpn %05X, tag %08X, data %08X, "
	"tlbacc %08X, tlbmisc %08X, pteaddr %08X\n",
	way, vpn, entry->tag, entry->data,
	env->regs[CR_TLBACC], env->regs[CR_TLBMISC],
	env->regs[CR_PTEADDR]));
	} else {
	env->regs[CR_TLBMISC] = v;
	}

	env->mmu.tlbmisc_wr = v;
	break;

	case CR_PTEADDR:
	MMU_LOG(qemu_log("PTEADDR: PTBASE %03X, VPN %05X\n",
	v >> CR_PTEADDR_PTBASE_SHIFT,
	(v & CR_PTEADDR_VPN_MASK) >> CR_PTEADDR_VPN_SHIFT));

	/* Writes to PTEADDR don't change the read-back VPN value */
	env->regs[CR_PTEADDR] = (v & ~CR_PTEADDR_VPN_MASK) \|
	(env->regs[CR_PTEADDR] & CR_PTEADDR_VPN_MASK);
	env->mmu.pteaddr_wr = v;
	break;

	default:
	break;
	}
	}

	void mmu_init(CPUNios2State *env)
	{
	Nios2CPU *cpu = nios2_env_get_cpu(env);
	Nios2MMU *mmu = &env->mmu;

	MMU_LOG(qemu_log("mmu_init\n"));

	mmu->tlb_entry_mask = (cpu->tlb_num_entries / cpu->tlb_num_ways) - 1;
	mmu->tlb = g_new0(Nios2TLBEntry, cpu->tlb_num_entries);
	}

	void dump_mmu(FILE f, fprintf_function cpu_fprintf, CPUNios2State env)
	{
	Nios2CPU *cpu = nios2_env_get_cpu(env);
	int i;

	cpu_fprintf(f, "MMU: ways %d, entries %d, pid bits %d\n",
	cpu->tlb_num_ways, cpu->tlb_num_entries,
	cpu->pid_num_bits);

	for (i = 0; i < cpu->tlb_num_entries; i++) {
	Nios2TLBEntry *entry = &env->mmu.tlb[i];
	cpu_fprintf(f, "TLB[%d] = %08X %08X %c VPN %05X "
	"PID %02X %c PFN %05X %c%c%c%c\n",
	i, entry->tag, entry->data,
	(entry->tag & (1 << 10)) ? 'V' : '-',
	entry->tag >> 12,
	entry->tag & ((1 << cpu->pid_num_bits) - 1),
	(entry->tag & (1 << 11)) ? 'G' : '-',
	entry->data & CR_TLBACC_PFN_MASK,
	(entry->data & CR_TLBACC_C) ? 'C' : '-',
	(entry->data & CR_TLBACC_R) ? 'R' : '-',
	(entry->data & CR_TLBACC_W) ? 'W' : '-',
	(entry->data & CR_TLBACC_X) ? 'X' : '-');
	}
	}

	#endif /* !CONFIG_USER_ONLY */