Introduce Virtio-loopback epsilon release:

Epsilon release introduces a new compatibility layer which make virtio-loopback
design to work with QEMU and rust-vmm vhost-user backend without require any
changes.

Signed-off-by: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
Change-Id: I52e57563e08a7d0bdc002f8e928ee61ba0c53dd9

1 files changed, 175 insertions, 0 deletions

diff --git a/migration/page_cache.c b/migration/page_cache.c
new file mode 100644
index 000000000..6d4f7a9bb
--- /dev/null
+++ b/migration/page_cache.c
@@ -0,0 +1,175 @@
+/*
+ * Page cache for QEMU
+ * The cache is base on a hash of the page address
+ *
+ * Copyright 2012 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ *  Orit Wasserman  <owasserm@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+
+#include "qapi/qmp/qerror.h"
+#include "qapi/error.h"
+#include "qemu/host-utils.h"
+#include "page_cache.h"
+#include "trace.h"
+
+/* the page in cache will not be replaced in two cycles */
+#define CACHED_PAGE_LIFETIME 2
+
+typedef struct CacheItem CacheItem;
+
+struct CacheItem {
+    uint64_t it_addr;
+    uint64_t it_age;
+    uint8_t *it_data;
+};
+
+struct PageCache {
+    CacheItem *page_cache;
+    size_t page_size;
+    size_t max_num_items;
+    size_t num_items;
+};
+
+PageCache *cache_init(uint64_t new_size, size_t page_size, Error **errp)
+{
+    int64_t i;
+    size_t num_pages = new_size / page_size;
+    PageCache *cache;
+
+    if (new_size < page_size) {
+        error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
+                   "is smaller than one target page size");
+        return NULL;
+    }
+
+    /* round down to the nearest power of 2 */
+    if (!is_power_of_2(num_pages)) {
+        error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
+                   "is not a power of two number of pages");
+        return NULL;
+    }
+
+    /* We prefer not to abort if there is no memory */
+    cache = g_try_malloc(sizeof(*cache));
+    if (!cache) {
+        error_setg(errp, "Failed to allocate cache");
+        return NULL;
+    }
+    cache->page_size = page_size;
+    cache->num_items = 0;
+    cache->max_num_items = num_pages;
+
+    trace_migration_pagecache_init(cache->max_num_items);
+
+    /* We prefer not to abort if there is no memory */
+    cache->page_cache = g_try_malloc((cache->max_num_items) *
+                                     sizeof(*cache->page_cache));
+    if (!cache->page_cache) {
+        error_setg(errp, "Failed to allocate page cache");
+        g_free(cache);
+        return NULL;
+    }
+
+    for (i = 0; i < cache->max_num_items; i++) {
+        cache->page_cache[i].it_data = NULL;
+        cache->page_cache[i].it_age = 0;
+        cache->page_cache[i].it_addr = -1;
+    }
+
+    return cache;
+}
+
+void cache_fini(PageCache *cache)
+{
+    int64_t i;
+
+    g_assert(cache);
+    g_assert(cache->page_cache);
+
+    for (i = 0; i < cache->max_num_items; i++) {
+        g_free(cache->page_cache[i].it_data);
+    }
+
+    g_free(cache->page_cache);
+    cache->page_cache = NULL;
+    g_free(cache);
+}
+
+static size_t cache_get_cache_pos(const PageCache *cache,
+                                  uint64_t address)
+{
+    g_assert(cache->max_num_items);
+    return (address / cache->page_size) & (cache->max_num_items - 1);
+}
+
+static CacheItem *cache_get_by_addr(const PageCache *cache, uint64_t addr)
+{
+    size_t pos;
+
+    g_assert(cache);
+    g_assert(cache->page_cache);
+
+    pos = cache_get_cache_pos(cache, addr);
+
+    return &cache->page_cache[pos];
+}
+
+uint8_t *get_cached_data(const PageCache *cache, uint64_t addr)
+{
+    return cache_get_by_addr(cache, addr)->it_data;
+}
+
+bool cache_is_cached(const PageCache *cache, uint64_t addr,
+                     uint64_t current_age)
+{
+    CacheItem *it;
+
+    it = cache_get_by_addr(cache, addr);
+
+    if (it->it_addr == addr) {
+        /* update the it_age when the cache hit */
+        it->it_age = current_age;
+        return true;
+    }
+    return false;
+}
+
+int cache_insert(PageCache *cache, uint64_t addr, const uint8_t *pdata,
+                 uint64_t current_age)
+{
+
+    CacheItem *it;
+
+    /* actual update of entry */
+    it = cache_get_by_addr(cache, addr);
+
+    if (it->it_data && it->it_addr != addr &&
+        it->it_age + CACHED_PAGE_LIFETIME > current_age) {
+        /* the cache page is fresh, don't replace it */
+        return -1;
+    }
+    /* allocate page */
+    if (!it->it_data) {
+        it->it_data = g_try_malloc(cache->page_size);
+        if (!it->it_data) {
+            trace_migration_pagecache_insert();
+            return -1;
+        }
+        cache->num_items++;
+    }
+
+    memcpy(it->it_data, pdata, cache->page_size);
+
+    it->it_age = current_age;
+    it->it_addr = addr;
+
+    return 0;
+}