contrib/plugins/cache.c - qemu - Git at Google

 /*
  * Copyright (C) 2021, Mahmoud Mandour <ma.mandourr@gmail.com>
  *
  * License: GNU GPL, version 2 or later.
  *   See the COPYING file in the top-level directory.
  */

 #include <inttypes.h>
 #include <stdio.h>
 #include <glib.h>

 #include <qemu-plugin.h>

 QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION;

 static enum qemu_plugin_mem_rw rw = QEMU_PLUGIN_MEM_RW;

 static GHashTable *miss_ht;

 static GMutex mtx;
 static GRand *rng;

 static int limit;
 static bool sys;

 static uint64_t dmem_accesses;
 static uint64_t dmisses;

 static uint64_t imem_accesses;
 static uint64_t imisses;

 enum EvictionPolicy {
     LRU,
     FIFO,
     RAND,
 };

 enum EvictionPolicy policy;

 /*
  * A CacheSet is a set of cache blocks. A memory block that maps to a set can be
  * put in any of the blocks inside the set. The number of block per set is
  * called the associativity (assoc).
  *
  * Each block contains the the stored tag and a valid bit. Since this is not
  * a functional simulator, the data itself is not stored. We only identify
  * whether a block is in the cache or not by searching for its tag.
  *
  * In order to search for memory data in the cache, the set identifier and tag
  * are extracted from the address and the set is probed to see whether a tag
  * match occur.
  *
  * An address is logically divided into three portions: The block offset,
  * the set number, and the tag.
  *
  * The set number is used to identify the set in which the block may exist.
  * The tag is compared against all the tags of a set to search for a match. If a
  * match is found, then the access is a hit.
  *
  * The CacheSet also contains bookkeaping information about eviction details.
  */

 typedef struct {
     uint64_t tag;
     bool valid;
 } CacheBlock;

 typedef struct {
     CacheBlock *blocks;
     uint64_t *lru_priorities;
     uint64_t lru_gen_counter;
     GQueue *fifo_queue;
 } CacheSet;

 typedef struct {
     CacheSet *sets;
     int num_sets;
     int cachesize;
     int assoc;
     int blksize_shift;
     uint64_t set_mask;
     uint64_t tag_mask;
 } Cache;

 typedef struct {
     char *disas_str;
     const char *symbol;
     uint64_t addr;
     uint64_t dmisses;
     uint64_t imisses;
 } InsnData;

 void (*update_hit)(Cache *cache, int set, int blk);
 void (*update_miss)(Cache *cache, int set, int blk);

 void (*metadata_init)(Cache *cache);
 void (*metadata_destroy)(Cache *cache);

 Cache *dcache, *icache;

 static int pow_of_two(int num)
 {
     g_assert((num & (num - 1)) == 0);
     int ret = 0;
     while (num /= 2) {
         ret++;
     }
     return ret;
 }

 /*
  * LRU evection policy: For each set, a generation counter is maintained
  * alongside a priority array.
  *
  * On each set access, the generation counter is incremented.
  *
  * On a cache hit: The hit-block is assigned the current generation counter,
  * indicating that it is the most recently used block.
  *
  * On a cache miss: The block with the least priority is searched and replaced
  * with the newly-cached block, of which the priority is set to the current
  * generation number.
  */

 static void lru_priorities_init(Cache *cache)
 {
     int i;

     for (i = 0; i < cache->num_sets; i++) {
         cache->sets[i].lru_priorities = g_new0(uint64_t, cache->assoc);
         cache->sets[i].lru_gen_counter = 0;
     }
 }

 static void lru_update_blk(Cache *cache, int set_idx, int blk_idx)
 {
     CacheSet *set = &cache->sets[set_idx];
     set->lru_priorities[blk_idx] = cache->sets[set_idx].lru_gen_counter;
     set->lru_gen_counter++;
 }

 static int lru_get_lru_block(Cache *cache, int set_idx)
 {
     int i, min_idx, min_priority;

     min_priority = cache->sets[set_idx].lru_priorities[0];
     min_idx = 0;

     for (i = 1; i < cache->assoc; i++) {
         if (cache->sets[set_idx].lru_priorities[i] < min_priority) {
             min_priority = cache->sets[set_idx].lru_priorities[i];
             min_idx = i;
         }
     }
     return min_idx;
 }

 static void lru_priorities_destroy(Cache *cache)
 {
     int i;

     for (i = 0; i < cache->num_sets; i++) {
         g_free(cache->sets[i].lru_priorities);
     }
 }

 /*
  * FIFO eviction policy: a FIFO queue is maintained for each CacheSet that
  * stores accesses to the cache.
  *
  * On a compulsory miss: The block index is enqueued to the fifo_queue to
  * indicate that it's the latest cached block.
  *
  * On a conflict miss: The first-in block is removed from the cache and the new
  * block is put in its place and enqueued to the FIFO queue.
  */

 static void fifo_init(Cache *cache)
 {
     int i;

     for (i = 0; i < cache->num_sets; i++) {
         cache->sets[i].fifo_queue = g_queue_new();
     }
 }

 static int fifo_get_first_block(Cache *cache, int set)
 {
     GQueue *q = cache->sets[set].fifo_queue;
     return GPOINTER_TO_INT(g_queue_pop_tail(q));
 }

 static void fifo_update_on_miss(Cache *cache, int set, int blk_idx)
 {
     GQueue *q = cache->sets[set].fifo_queue;
     g_queue_push_head(q, GINT_TO_POINTER(blk_idx));
 }

 static void fifo_destroy(Cache *cache)
 {
     int i;

     for (i = 0; i < cache->assoc; i++) {
         g_queue_free(cache->sets[i].fifo_queue);
     }
 }

 static inline uint64_t extract_tag(Cache *cache, uint64_t addr)
 {
     return addr & cache->tag_mask;
 }

 static inline uint64_t extract_set(Cache *cache, uint64_t addr)
 {
     return (addr & cache->set_mask) >> cache->blksize_shift;
 }

 static const char *cache_config_error(int blksize, int assoc, int cachesize)
 {
     if (cachesize % blksize != 0) {
         return "cache size must be divisible by block size";
     } else if (cachesize % (blksize * assoc) != 0) {
         return "cache size must be divisible by set size (assoc * block size)";
     } else {
         return NULL;
     }
 }

 static bool bad_cache_params(int blksize, int assoc, int cachesize)
 {
     return (cachesize % blksize) != 0 || (cachesize % (blksize * assoc) != 0);
 }

 static Cache *cache_init(int blksize, int assoc, int cachesize)
 {
     if (bad_cache_params(blksize, assoc, cachesize)) {
         return NULL;
     }

     Cache *cache;
     int i;
     uint64_t blk_mask;

     cache = g_new(Cache, 1);
     cache->assoc = assoc;
     cache->cachesize = cachesize;
     cache->num_sets = cachesize / (blksize * assoc);
     cache->sets = g_new(CacheSet, cache->num_sets);
     cache->blksize_shift = pow_of_two(blksize);

     for (i = 0; i < cache->num_sets; i++) {
         cache->sets[i].blocks = g_new0(CacheBlock, assoc);
     }

     blk_mask = blksize - 1;
     cache->set_mask = ((cache->num_sets - 1) << cache->blksize_shift);
     cache->tag_mask = ~(cache->set_mask | blk_mask);

     if (metadata_init) {
         metadata_init(cache);
     }

     return cache;
 }

 static int get_invalid_block(Cache *cache, uint64_t set)
 {
     int i;

     for (i = 0; i < cache->assoc; i++) {
         if (!cache->sets[set].blocks[i].valid) {
             return i;
         }
     }

     return -1;
 }

 static int get_replaced_block(Cache *cache, int set)
 {
     switch (policy) {
     case RAND:
         return g_rand_int_range(rng, 0, cache->assoc);
     case LRU:
         return lru_get_lru_block(cache, set);
     case FIFO:
         return fifo_get_first_block(cache, set);
     default:
         g_assert_not_reached();
     }
 }

 static int in_cache(Cache *cache, uint64_t addr)
 {
     int i;
     uint64_t tag, set;

     tag = extract_tag(cache, addr);
     set = extract_set(cache, addr);

     for (i = 0; i < cache->assoc; i++) {
         if (cache->sets[set].blocks[i].tag == tag &&
                 cache->sets[set].blocks[i].valid) {
             return i;
         }
     }

     return -1;
 }

 /**
  * access_cache(): Simulate a cache access
  * @cache: The cache under simulation
  * @addr: The address of the requested memory location
  *
  * Returns true if the requsted data is hit in the cache and false when missed.
  * The cache is updated on miss for the next access.
  */
 static bool access_cache(Cache *cache, uint64_t addr)
 {
     int hit_blk, replaced_blk;
     uint64_t tag, set;

     tag = extract_tag(cache, addr);
     set = extract_set(cache, addr);

     hit_blk = in_cache(cache, addr);
     if (hit_blk != -1) {
         if (update_hit) {
             update_hit(cache, set, hit_blk);
         }
         return true;
     }

     replaced_blk = get_invalid_block(cache, set);

     if (replaced_blk == -1) {
         replaced_blk = get_replaced_block(cache, set);
     }

     if (update_miss) {
         update_miss(cache, set, replaced_blk);
     }

     cache->sets[set].blocks[replaced_blk].tag = tag;
     cache->sets[set].blocks[replaced_blk].valid = true;

     return false;
 }

 static void vcpu_mem_access(unsigned int vcpu_index, qemu_plugin_meminfo_t info,
                             uint64_t vaddr, void *userdata)
 {
     uint64_t effective_addr;
     struct qemu_plugin_hwaddr *hwaddr;
     InsnData *insn;

     g_mutex_lock(&mtx);
     hwaddr = qemu_plugin_get_hwaddr(info, vaddr);
     if (hwaddr && qemu_plugin_hwaddr_is_io(hwaddr)) {
         g_mutex_unlock(&mtx);
         return;
     }

     effective_addr = hwaddr ? qemu_plugin_hwaddr_phys_addr(hwaddr) : vaddr;

     if (!access_cache(dcache, effective_addr)) {
         insn = (InsnData *) userdata;
         insn->dmisses++;
         dmisses++;
     }
     dmem_accesses++;
     g_mutex_unlock(&mtx);
 }

 static void vcpu_insn_exec(unsigned int vcpu_index, void *userdata)
 {
     uint64_t insn_addr;
     InsnData *insn;

     g_mutex_lock(&mtx);
     insn_addr = ((InsnData *) userdata)->addr;

     if (!access_cache(icache, insn_addr)) {
         insn = (InsnData *) userdata;
         insn->imisses++;
         imisses++;
     }
     imem_accesses++;
     g_mutex_unlock(&mtx);
 }

 static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
 {
     size_t n_insns;
     size_t i;
     InsnData *data;

     n_insns = qemu_plugin_tb_n_insns(tb);
     for (i = 0; i < n_insns; i++) {
         struct qemu_plugin_insn *insn = qemu_plugin_tb_get_insn(tb, i);
         uint64_t effective_addr;

         if (sys) {
             effective_addr = (uint64_t) qemu_plugin_insn_haddr(insn);
         } else {
             effective_addr = (uint64_t) qemu_plugin_insn_vaddr(insn);
         }

         /*
          * Instructions might get translated multiple times, we do not create
          * new entries for those instructions. Instead, we fetch the same
          * entry from the hash table and register it for the callback again.
          */
         g_mutex_lock(&mtx);
         data = g_hash_table_lookup(miss_ht, GUINT_TO_POINTER(effective_addr));
         if (data == NULL) {
             data = g_new0(InsnData, 1);
             data->disas_str = qemu_plugin_insn_disas(insn);
             data->symbol = qemu_plugin_insn_symbol(insn);
             data->addr = effective_addr;
             g_hash_table_insert(miss_ht, GUINT_TO_POINTER(effective_addr),
                                (gpointer) data);
         }
         g_mutex_unlock(&mtx);

         qemu_plugin_register_vcpu_mem_cb(insn, vcpu_mem_access,
                                          QEMU_PLUGIN_CB_NO_REGS,
                                          rw, data);

         qemu_plugin_register_vcpu_insn_exec_cb(insn, vcpu_insn_exec,
                                                QEMU_PLUGIN_CB_NO_REGS, data);
     }
 }

 static void insn_free(gpointer data)
 {
     InsnData *insn = (InsnData *) data;
     g_free(insn->disas_str);
     g_free(insn);
 }

 static void cache_free(Cache *cache)
 {
     for (int i = 0; i < cache->num_sets; i++) {
         g_free(cache->sets[i].blocks);
     }

     if (metadata_destroy) {
         metadata_destroy(cache);
     }

     g_free(cache->sets);
     g_free(cache);
 }

 static int dcmp(gconstpointer a, gconstpointer b)
 {
     InsnData *insn_a = (InsnData *) a;
     InsnData *insn_b = (InsnData *) b;

     return insn_a->dmisses < insn_b->dmisses ? 1 : -1;
 }

 static int icmp(gconstpointer a, gconstpointer b)
 {
     InsnData *insn_a = (InsnData *) a;
     InsnData *insn_b = (InsnData *) b;

     return insn_a->imisses < insn_b->imisses ? 1 : -1;
 }

 static void log_stats()
 {
     g_autoptr(GString) rep = g_string_new("");
     g_string_append_printf(rep,
         "Data accesses: %lu, Misses: %lu\nMiss rate: %lf%%\n\n",
         dmem_accesses,
         dmisses,
         ((double) dmisses / (double) dmem_accesses) * 100.0);

     g_string_append_printf(rep,
         "Instruction accesses: %lu, Misses: %lu\nMiss rate: %lf%%\n\n",
         imem_accesses,
         imisses,
         ((double) imisses / (double) imem_accesses) * 100.0);

     qemu_plugin_outs(rep->str);
 }

 static void log_top_insns()
 {
     int i;
     GList *curr, *miss_insns;
     InsnData *insn;

     miss_insns = g_hash_table_get_values(miss_ht);
     miss_insns = g_list_sort(miss_insns, dcmp);
     g_autoptr(GString) rep = g_string_new("");
     g_string_append_printf(rep, "%s", "address, data misses, instruction\n");

     for (curr = miss_insns, i = 0; curr && i < limit; i++, curr = curr->next) {
         insn = (InsnData *) curr->data;
         g_string_append_printf(rep, "0x%" PRIx64, insn->addr);
         if (insn->symbol) {
             g_string_append_printf(rep, " (%s)", insn->symbol);
         }
         g_string_append_printf(rep, ", %ld, %s\n", insn->dmisses,
                                insn->disas_str);
     }

     miss_insns = g_list_sort(miss_insns, icmp);
     g_string_append_printf(rep, "%s", "\naddress, fetch misses, instruction\n");

     for (curr = miss_insns, i = 0; curr && i < limit; i++, curr = curr->next) {
         insn = (InsnData *) curr->data;
         g_string_append_printf(rep, "0x%" PRIx64, insn->addr);
         if (insn->symbol) {
             g_string_append_printf(rep, " (%s)", insn->symbol);
         }
         g_string_append_printf(rep, ", %ld, %s\n", insn->imisses,
                                insn->disas_str);
     }

     qemu_plugin_outs(rep->str);
     g_list_free(miss_insns);
 }

 static void plugin_exit(qemu_plugin_id_t id, void *p)
 {
     log_stats();
     log_top_insns();

     cache_free(dcache);
     cache_free(icache);

     g_hash_table_destroy(miss_ht);
 }

 static void policy_init()
 {
     switch (policy) {
     case LRU:
         update_hit = lru_update_blk;
         update_miss = lru_update_blk;
         metadata_init = lru_priorities_init;
         metadata_destroy = lru_priorities_destroy;
         break;
     case FIFO:
         update_miss = fifo_update_on_miss;
         metadata_init = fifo_init;
         metadata_destroy = fifo_destroy;
         break;
     case RAND:
         rng = g_rand_new();
         break;
     default:
         g_assert_not_reached();
     }
 }

 QEMU_PLUGIN_EXPORT
 int qemu_plugin_install(qemu_plugin_id_t id, const qemu_info_t *info,
                         int argc, char **argv)
 {
     int i;
     int iassoc, iblksize, icachesize;
     int dassoc, dblksize, dcachesize;

     limit = 32;
     sys = info->system_emulation;

     dassoc = 8;
     dblksize = 64;
     dcachesize = dblksize * dassoc * 32;

     iassoc = 8;
     iblksize = 64;
     icachesize = iblksize * iassoc * 32;

     policy = LRU;

     for (i = 0; i < argc; i++) {
         char *opt = argv[i];
         if (g_str_has_prefix(opt, "iblksize=")) {
             iblksize = g_ascii_strtoll(opt + 9, NULL, 10);
         } else if (g_str_has_prefix(opt, "iassoc=")) {
             iassoc = g_ascii_strtoll(opt + 7, NULL, 10);
         } else if (g_str_has_prefix(opt, "icachesize=")) {
             icachesize = g_ascii_strtoll(opt + 11, NULL, 10);
         } else if (g_str_has_prefix(opt, "dblksize=")) {
             dblksize = g_ascii_strtoll(opt + 9, NULL, 10);
         } else if (g_str_has_prefix(opt, "dassoc=")) {
             dassoc = g_ascii_strtoll(opt + 7, NULL, 10);
         } else if (g_str_has_prefix(opt, "dcachesize=")) {
             dcachesize = g_ascii_strtoll(opt + 11, NULL, 10);
         } else if (g_str_has_prefix(opt, "limit=")) {
             limit = g_ascii_strtoll(opt + 6, NULL, 10);
         } else if (g_str_has_prefix(opt, "evict=")) {
             gchar *p = opt + 6;
             if (g_strcmp0(p, "rand") == 0) {
                 policy = RAND;
             } else if (g_strcmp0(p, "lru") == 0) {
                 policy = LRU;
             } else if (g_strcmp0(p, "fifo") == 0) {
                 policy = FIFO;
             } else {
                 fprintf(stderr, "invalid eviction policy: %s\n", opt);
                 return -1;
             }
         } else {
             fprintf(stderr, "option parsing failed: %s\n", opt);
             return -1;
         }
     }

     policy_init();

     dcache = cache_init(dblksize, dassoc, dcachesize);
     if (!dcache) {
         const char *err = cache_config_error(dblksize, dassoc, dcachesize);
         fprintf(stderr, "dcache cannot be constructed from given parameters\n");
         fprintf(stderr, "%s\n", err);
         return -1;
     }

     icache = cache_init(iblksize, iassoc, icachesize);
     if (!icache) {
         const char *err = cache_config_error(iblksize, iassoc, icachesize);
         fprintf(stderr, "icache cannot be constructed from given parameters\n");
         fprintf(stderr, "%s\n", err);
         return -1;
     }

     qemu_plugin_register_vcpu_tb_trans_cb(id, vcpu_tb_trans);
     qemu_plugin_register_atexit_cb(id, plugin_exit, NULL);

     miss_ht = g_hash_table_new_full(NULL, g_direct_equal, NULL, insn_free);

     return 0;
 }
	/*
	* Copyright (C) 2021, Mahmoud Mandour <ma.mandourr@gmail.com>
	*
	* License: GNU GPL, version 2 or later.
	* See the COPYING file in the top-level directory.
	*/

	#include <inttypes.h>
	#include <stdio.h>
	#include <glib.h>

	#include <qemu-plugin.h>

	QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION;

	static enum qemu_plugin_mem_rw rw = QEMU_PLUGIN_MEM_RW;

	static GHashTable *miss_ht;

	static GMutex mtx;
	static GRand *rng;

	static int limit;
	static bool sys;

	static uint64_t dmem_accesses;
	static uint64_t dmisses;

	static uint64_t imem_accesses;
	static uint64_t imisses;

	enum EvictionPolicy {
	LRU,
	FIFO,
	RAND,
	};

	enum EvictionPolicy policy;

	/*
	* A CacheSet is a set of cache blocks. A memory block that maps to a set can be
	* put in any of the blocks inside the set. The number of block per set is
	* called the associativity (assoc).
	*
	* Each block contains the the stored tag and a valid bit. Since this is not
	* a functional simulator, the data itself is not stored. We only identify
	* whether a block is in the cache or not by searching for its tag.
	*
	* In order to search for memory data in the cache, the set identifier and tag
	* are extracted from the address and the set is probed to see whether a tag
	* match occur.
	*
	* An address is logically divided into three portions: The block offset,
	* the set number, and the tag.
	*
	* The set number is used to identify the set in which the block may exist.
	* The tag is compared against all the tags of a set to search for a match. If a
	* match is found, then the access is a hit.
	*
	* The CacheSet also contains bookkeaping information about eviction details.
	*/

	typedef struct {
	uint64_t tag;
	bool valid;
	} CacheBlock;

	typedef struct {
	CacheBlock *blocks;
	uint64_t *lru_priorities;
	uint64_t lru_gen_counter;
	GQueue *fifo_queue;
	} CacheSet;

	typedef struct {
	CacheSet *sets;
	int num_sets;
	int cachesize;
	int assoc;
	int blksize_shift;
	uint64_t set_mask;
	uint64_t tag_mask;
	} Cache;

	typedef struct {
	char *disas_str;
	const char *symbol;
	uint64_t addr;
	uint64_t dmisses;
	uint64_t imisses;
	} InsnData;

	void (update_hit)(Cache cache, int set, int blk);
	void (update_miss)(Cache cache, int set, int blk);

	void (metadata_init)(Cache cache);
	void (metadata_destroy)(Cache cache);

	Cache dcache, icache;

	static int pow_of_two(int num)
	{
	g_assert((num & (num - 1)) == 0);
	int ret = 0;
	while (num /= 2) {
	ret++;
	}
	return ret;
	}

	/*
	* LRU evection policy: For each set, a generation counter is maintained
	* alongside a priority array.
	*
	* On each set access, the generation counter is incremented.
	*
	* On a cache hit: The hit-block is assigned the current generation counter,
	* indicating that it is the most recently used block.
	*
	* On a cache miss: The block with the least priority is searched and replaced
	* with the newly-cached block, of which the priority is set to the current
	* generation number.
	*/

	static void lru_priorities_init(Cache *cache)
	{
	int i;

	for (i = 0; i < cache->num_sets; i++) {
	cache->sets[i].lru_priorities = g_new0(uint64_t, cache->assoc);
	cache->sets[i].lru_gen_counter = 0;
	}
	}

	static void lru_update_blk(Cache *cache, int set_idx, int blk_idx)
	{
	CacheSet *set = &cache->sets[set_idx];
	set->lru_priorities[blk_idx] = cache->sets[set_idx].lru_gen_counter;
	set->lru_gen_counter++;
	}

	static int lru_get_lru_block(Cache *cache, int set_idx)
	{
	int i, min_idx, min_priority;

	min_priority = cache->sets[set_idx].lru_priorities[0];
	min_idx = 0;

	for (i = 1; i < cache->assoc; i++) {
	if (cache->sets[set_idx].lru_priorities[i] < min_priority) {
	min_priority = cache->sets[set_idx].lru_priorities[i];
	min_idx = i;
	}
	}
	return min_idx;
	}

	static void lru_priorities_destroy(Cache *cache)
	{
	int i;

	for (i = 0; i < cache->num_sets; i++) {
	g_free(cache->sets[i].lru_priorities);
	}
	}

	/*
	* FIFO eviction policy: a FIFO queue is maintained for each CacheSet that
	* stores accesses to the cache.
	*
	* On a compulsory miss: The block index is enqueued to the fifo_queue to
	* indicate that it's the latest cached block.
	*
	* On a conflict miss: The first-in block is removed from the cache and the new
	* block is put in its place and enqueued to the FIFO queue.
	*/

	static void fifo_init(Cache *cache)
	{
	int i;

	for (i = 0; i < cache->num_sets; i++) {
	cache->sets[i].fifo_queue = g_queue_new();
	}
	}

	static int fifo_get_first_block(Cache *cache, int set)
	{
	GQueue *q = cache->sets[set].fifo_queue;
	return GPOINTER_TO_INT(g_queue_pop_tail(q));
	}

	static void fifo_update_on_miss(Cache *cache, int set, int blk_idx)
	{
	GQueue *q = cache->sets[set].fifo_queue;
	g_queue_push_head(q, GINT_TO_POINTER(blk_idx));
	}

	static void fifo_destroy(Cache *cache)
	{
	int i;

	for (i = 0; i < cache->assoc; i++) {
	g_queue_free(cache->sets[i].fifo_queue);
	}
	}

	static inline uint64_t extract_tag(Cache *cache, uint64_t addr)
	{
	return addr & cache->tag_mask;
	}

	static inline uint64_t extract_set(Cache *cache, uint64_t addr)
	{
	return (addr & cache->set_mask) >> cache->blksize_shift;
	}

	static const char *cache_config_error(int blksize, int assoc, int cachesize)
	{
	if (cachesize % blksize != 0) {
	return "cache size must be divisible by block size";
	} else if (cachesize % (blksize * assoc) != 0) {
	return "cache size must be divisible by set size (assoc * block size)";
	} else {
	return NULL;
	}
	}

	static bool bad_cache_params(int blksize, int assoc, int cachesize)
	{
	return (cachesize % blksize) != 0 \|\| (cachesize % (blksize * assoc) != 0);
	}

	static Cache *cache_init(int blksize, int assoc, int cachesize)
	{
	if (bad_cache_params(blksize, assoc, cachesize)) {
	return NULL;
	}

	Cache *cache;
	int i;
	uint64_t blk_mask;

	cache = g_new(Cache, 1);
	cache->assoc = assoc;
	cache->cachesize = cachesize;
	cache->num_sets = cachesize / (blksize * assoc);
	cache->sets = g_new(CacheSet, cache->num_sets);
	cache->blksize_shift = pow_of_two(blksize);

	for (i = 0; i < cache->num_sets; i++) {
	cache->sets[i].blocks = g_new0(CacheBlock, assoc);
	}

	blk_mask = blksize - 1;
	cache->set_mask = ((cache->num_sets - 1) << cache->blksize_shift);
	cache->tag_mask = ~(cache->set_mask \| blk_mask);

	if (metadata_init) {
	metadata_init(cache);
	}

	return cache;
	}

	static int get_invalid_block(Cache *cache, uint64_t set)
	{
	int i;

	for (i = 0; i < cache->assoc; i++) {
	if (!cache->sets[set].blocks[i].valid) {
	return i;
	}
	}

	return -1;
	}

	static int get_replaced_block(Cache *cache, int set)
	{
	switch (policy) {
	case RAND:
	return g_rand_int_range(rng, 0, cache->assoc);
	case LRU:
	return lru_get_lru_block(cache, set);
	case FIFO:
	return fifo_get_first_block(cache, set);
	default:
	g_assert_not_reached();
	}
	}

	static int in_cache(Cache *cache, uint64_t addr)
	{
	int i;
	uint64_t tag, set;

	tag = extract_tag(cache, addr);
	set = extract_set(cache, addr);

	for (i = 0; i < cache->assoc; i++) {
	if (cache->sets[set].blocks[i].tag == tag &&
	cache->sets[set].blocks[i].valid) {
	return i;
	}
	}

	return -1;
	}

	/**
	* access_cache(): Simulate a cache access
	* @cache: The cache under simulation
	* @addr: The address of the requested memory location
	*
	* Returns true if the requsted data is hit in the cache and false when missed.
	* The cache is updated on miss for the next access.
	*/
	static bool access_cache(Cache *cache, uint64_t addr)
	{
	int hit_blk, replaced_blk;
	uint64_t tag, set;

	tag = extract_tag(cache, addr);
	set = extract_set(cache, addr);

	hit_blk = in_cache(cache, addr);
	if (hit_blk != -1) {
	if (update_hit) {
	update_hit(cache, set, hit_blk);
	}
	return true;
	}

	replaced_blk = get_invalid_block(cache, set);

	if (replaced_blk == -1) {
	replaced_blk = get_replaced_block(cache, set);
	}

	if (update_miss) {
	update_miss(cache, set, replaced_blk);
	}

	cache->sets[set].blocks[replaced_blk].tag = tag;
	cache->sets[set].blocks[replaced_blk].valid = true;

	return false;
	}

	static void vcpu_mem_access(unsigned int vcpu_index, qemu_plugin_meminfo_t info,
	uint64_t vaddr, void *userdata)
	{
	uint64_t effective_addr;
	struct qemu_plugin_hwaddr *hwaddr;
	InsnData *insn;

	g_mutex_lock(&mtx);
	hwaddr = qemu_plugin_get_hwaddr(info, vaddr);
	if (hwaddr && qemu_plugin_hwaddr_is_io(hwaddr)) {
	g_mutex_unlock(&mtx);
	return;
	}

	effective_addr = hwaddr ? qemu_plugin_hwaddr_phys_addr(hwaddr) : vaddr;

	if (!access_cache(dcache, effective_addr)) {
	insn = (InsnData *) userdata;
	insn->dmisses++;
	dmisses++;
	}
	dmem_accesses++;
	g_mutex_unlock(&mtx);
	}

	static void vcpu_insn_exec(unsigned int vcpu_index, void *userdata)
	{
	uint64_t insn_addr;
	InsnData *insn;

	g_mutex_lock(&mtx);
	insn_addr = ((InsnData *) userdata)->addr;

	if (!access_cache(icache, insn_addr)) {
	insn = (InsnData *) userdata;
	insn->imisses++;
	imisses++;
	}
	imem_accesses++;
	g_mutex_unlock(&mtx);
	}

	static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
	{
	size_t n_insns;
	size_t i;
	InsnData *data;

	n_insns = qemu_plugin_tb_n_insns(tb);
	for (i = 0; i < n_insns; i++) {
	struct qemu_plugin_insn *insn = qemu_plugin_tb_get_insn(tb, i);
	uint64_t effective_addr;

	if (sys) {
	effective_addr = (uint64_t) qemu_plugin_insn_haddr(insn);
	} else {
	effective_addr = (uint64_t) qemu_plugin_insn_vaddr(insn);
	}

	/*
	* Instructions might get translated multiple times, we do not create
	* new entries for those instructions. Instead, we fetch the same
	* entry from the hash table and register it for the callback again.
	*/
	g_mutex_lock(&mtx);
	data = g_hash_table_lookup(miss_ht, GUINT_TO_POINTER(effective_addr));
	if (data == NULL) {
	data = g_new0(InsnData, 1);
	data->disas_str = qemu_plugin_insn_disas(insn);
	data->symbol = qemu_plugin_insn_symbol(insn);
	data->addr = effective_addr;
	g_hash_table_insert(miss_ht, GUINT_TO_POINTER(effective_addr),
	(gpointer) data);
	}
	g_mutex_unlock(&mtx);

	qemu_plugin_register_vcpu_mem_cb(insn, vcpu_mem_access,
	QEMU_PLUGIN_CB_NO_REGS,
	rw, data);

	qemu_plugin_register_vcpu_insn_exec_cb(insn, vcpu_insn_exec,
	QEMU_PLUGIN_CB_NO_REGS, data);
	}
	}

	static void insn_free(gpointer data)
	{
	InsnData insn = (InsnData ) data;
	g_free(insn->disas_str);
	g_free(insn);
	}

	static void cache_free(Cache *cache)
	{
	for (int i = 0; i < cache->num_sets; i++) {
	g_free(cache->sets[i].blocks);
	}

	if (metadata_destroy) {
	metadata_destroy(cache);
	}

	g_free(cache->sets);
	g_free(cache);
	}

	static int dcmp(gconstpointer a, gconstpointer b)
	{
	InsnData insn_a = (InsnData ) a;
	InsnData insn_b = (InsnData ) b;

	return insn_a->dmisses < insn_b->dmisses ? 1 : -1;
	}

	static int icmp(gconstpointer a, gconstpointer b)
	{
	InsnData insn_a = (InsnData ) a;
	InsnData insn_b = (InsnData ) b;

	return insn_a->imisses < insn_b->imisses ? 1 : -1;
	}

	static void log_stats()
	{
	g_autoptr(GString) rep = g_string_new("");
	g_string_append_printf(rep,
	"Data accesses: %lu, Misses: %lu\nMiss rate: %lf%%\n\n",
	dmem_accesses,
	dmisses,
	((double) dmisses / (double) dmem_accesses) * 100.0);

	g_string_append_printf(rep,
	"Instruction accesses: %lu, Misses: %lu\nMiss rate: %lf%%\n\n",
	imem_accesses,
	imisses,
	((double) imisses / (double) imem_accesses) * 100.0);

	qemu_plugin_outs(rep->str);
	}

	static void log_top_insns()
	{
	int i;
	GList curr, miss_insns;
	InsnData *insn;

	miss_insns = g_hash_table_get_values(miss_ht);
	miss_insns = g_list_sort(miss_insns, dcmp);
	g_autoptr(GString) rep = g_string_new("");
	g_string_append_printf(rep, "%s", "address, data misses, instruction\n");

	for (curr = miss_insns, i = 0; curr && i < limit; i++, curr = curr->next) {
	insn = (InsnData *) curr->data;
	g_string_append_printf(rep, "0x%" PRIx64, insn->addr);
	if (insn->symbol) {
	g_string_append_printf(rep, " (%s)", insn->symbol);
	}
	g_string_append_printf(rep, ", %ld, %s\n", insn->dmisses,
	insn->disas_str);
	}

	miss_insns = g_list_sort(miss_insns, icmp);
	g_string_append_printf(rep, "%s", "\naddress, fetch misses, instruction\n");

	for (curr = miss_insns, i = 0; curr && i < limit; i++, curr = curr->next) {
	insn = (InsnData *) curr->data;
	g_string_append_printf(rep, "0x%" PRIx64, insn->addr);
	if (insn->symbol) {
	g_string_append_printf(rep, " (%s)", insn->symbol);
	}
	g_string_append_printf(rep, ", %ld, %s\n", insn->imisses,
	insn->disas_str);
	}

	qemu_plugin_outs(rep->str);
	g_list_free(miss_insns);
	}

	static void plugin_exit(qemu_plugin_id_t id, void *p)
	{
	log_stats();
	log_top_insns();

	cache_free(dcache);
	cache_free(icache);

	g_hash_table_destroy(miss_ht);
	}

	static void policy_init()
	{
	switch (policy) {
	case LRU:
	update_hit = lru_update_blk;
	update_miss = lru_update_blk;
	metadata_init = lru_priorities_init;
	metadata_destroy = lru_priorities_destroy;
	break;
	case FIFO:
	update_miss = fifo_update_on_miss;
	metadata_init = fifo_init;
	metadata_destroy = fifo_destroy;
	break;
	case RAND:
	rng = g_rand_new();
	break;
	default:
	g_assert_not_reached();
	}
	}

	QEMU_PLUGIN_EXPORT
	int qemu_plugin_install(qemu_plugin_id_t id, const qemu_info_t *info,
	int argc, char **argv)
	{
	int i;
	int iassoc, iblksize, icachesize;
	int dassoc, dblksize, dcachesize;

	limit = 32;
	sys = info->system_emulation;

	dassoc = 8;
	dblksize = 64;
	dcachesize = dblksize * dassoc * 32;

	iassoc = 8;
	iblksize = 64;
	icachesize = iblksize * iassoc * 32;

	policy = LRU;

	for (i = 0; i < argc; i++) {
	char *opt = argv[i];
	if (g_str_has_prefix(opt, "iblksize=")) {
	iblksize = g_ascii_strtoll(opt + 9, NULL, 10);
	} else if (g_str_has_prefix(opt, "iassoc=")) {
	iassoc = g_ascii_strtoll(opt + 7, NULL, 10);
	} else if (g_str_has_prefix(opt, "icachesize=")) {
	icachesize = g_ascii_strtoll(opt + 11, NULL, 10);
	} else if (g_str_has_prefix(opt, "dblksize=")) {
	dblksize = g_ascii_strtoll(opt + 9, NULL, 10);
	} else if (g_str_has_prefix(opt, "dassoc=")) {
	dassoc = g_ascii_strtoll(opt + 7, NULL, 10);
	} else if (g_str_has_prefix(opt, "dcachesize=")) {
	dcachesize = g_ascii_strtoll(opt + 11, NULL, 10);
	} else if (g_str_has_prefix(opt, "limit=")) {
	limit = g_ascii_strtoll(opt + 6, NULL, 10);
	} else if (g_str_has_prefix(opt, "evict=")) {
	gchar *p = opt + 6;
	if (g_strcmp0(p, "rand") == 0) {
	policy = RAND;
	} else if (g_strcmp0(p, "lru") == 0) {
	policy = LRU;
	} else if (g_strcmp0(p, "fifo") == 0) {
	policy = FIFO;
	} else {
	fprintf(stderr, "invalid eviction policy: %s\n", opt);
	return -1;
	}
	} else {
	fprintf(stderr, "option parsing failed: %s\n", opt);
	return -1;
	}
	}

	policy_init();

	dcache = cache_init(dblksize, dassoc, dcachesize);
	if (!dcache) {
	const char *err = cache_config_error(dblksize, dassoc, dcachesize);
	fprintf(stderr, "dcache cannot be constructed from given parameters\n");
	fprintf(stderr, "%s\n", err);
	return -1;
	}

	icache = cache_init(iblksize, iassoc, icachesize);
	if (!icache) {
	const char *err = cache_config_error(iblksize, iassoc, icachesize);
	fprintf(stderr, "icache cannot be constructed from given parameters\n");
	fprintf(stderr, "%s\n", err);
	return -1;
	}

	qemu_plugin_register_vcpu_tb_trans_cb(id, vcpu_tb_trans);
	qemu_plugin_register_atexit_cb(id, plugin_exit, NULL);

	miss_ht = g_hash_table_new_full(NULL, g_direct_equal, NULL, insn_free);

	return 0;
	}