[Qemu-devel] [RFC PATCH v4 13/28] COLO RAM: Flush cached RAM into SVM's memory

[zhanghailiang <zhang.zhanghailiang@huawei.com>]

During the time of VM's running, PVM/SVM may dirty some pages, we will transfer
PVM's dirty pages to SVM and store them into SVM's RAM cache at next checkpoint
time. So, the content of SVM's RAM cache will always be some with PVM's memory
after checkpoint.

Instead of flushing all content of SVM's RAM cache into SVM's MEMORY,
we do this in a more efficient way:
Only flush any page that dirtied by PVM or SVM since last checkpoint.
In this way, we ensure SVM's memory same with PVM's.

Besides, we must ensure flush RAM cache before load device state.

Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
Signed-off-by: Gonglei <arei.gonglei@huawei.com>
---
 arch_init.c                        | 92 ++++++++++++++++++++++++++++++++++++++
 include/migration/migration-colo.h |  1 +
 migration/colo.c                   |  1 -
 3 files changed, 93 insertions(+), 1 deletion(-)

diff --git a/arch_init.c b/arch_init.c
index f3f2460..2abb5d2 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -1154,6 +1154,7 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
 {
     int flags = 0, ret = 0;
     static uint64_t seq_iter;
+    bool need_flush = false;
 
     seq_iter++;
 
@@ -1221,6 +1222,8 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
                 ret = -EINVAL;
                 break;
             }
+
+            need_flush = true;
             ch = qemu_get_byte(f);
             ram_handle_compressed(host, ch, TARGET_PAGE_SIZE);
             break;
@@ -1231,6 +1234,8 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
                 ret = -EINVAL;
                 break;
             }
+
+            need_flush = true;
             qemu_get_buffer(f, host, TARGET_PAGE_SIZE);
             break;
         case RAM_SAVE_FLAG_XBZRLE:
@@ -1246,6 +1251,7 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
                 ret = -EINVAL;
                 break;
             }
+            need_flush = true;
             break;
         case RAM_SAVE_FLAG_EOS:
             /* normal exit */
@@ -1265,6 +1271,11 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
     }
 
     rcu_read_unlock();
+
+    if (!ret  && ram_cache_enable && need_flush) {
+        DPRINTF("Flush ram_cache\n");
+        colo_flush_ram_cache();
+    }
     DPRINTF("Completed load of VM with exit code %d seq iteration "
             "%" PRIu64 "\n", ret, seq_iter);
     return ret;
@@ -1332,6 +1343,87 @@ static void *memory_region_get_ram_cache_ptr(MemoryRegion *mr, RAMBlock *block)
     return block->host_cache + (addr - block->offset);
 }
 
+/* fix me: should this helper function be merged with
+ * migration_bitmap_find_and_reset_dirty ?
+ */
+static inline
+ram_addr_t host_bitmap_find_and_reset_dirty(MemoryRegion *mr,
+                                            ram_addr_t start)
+{
+    unsigned long base = mr->ram_addr >> TARGET_PAGE_BITS;
+    unsigned long nr = base + (start >> TARGET_PAGE_BITS);
+    uint64_t mr_size = TARGET_PAGE_ALIGN(memory_region_size(mr));
+    unsigned long size = base + (mr_size >> TARGET_PAGE_BITS);
+
+    unsigned long next;
+
+    next = find_next_bit(ram_list.dirty_memory[DIRTY_MEMORY_MIGRATION],
+                         size, nr);
+    if (next < size) {
+        clear_bit(next, ram_list.dirty_memory[DIRTY_MEMORY_MIGRATION]);
+    }
+    return (next - base) << TARGET_PAGE_BITS;
+}
+
+/*
+* Flush content of RAM cache into SVM's memory.
+* Only flush the pages that be dirtied by PVM or SVM or both.
+*/
+void colo_flush_ram_cache(void)
+{
+    RAMBlock *block = NULL;
+    void *dst_host;
+    void *src_host;
+    ram_addr_t ca  = 0, ha = 0;
+    bool got_ca = 0, got_ha = 0;
+    int64_t host_dirty = 0, both_dirty = 0;
+
+    address_space_sync_dirty_bitmap(&address_space_memory);
+    rcu_read_lock();
+    block = QLIST_FIRST_RCU(&ram_list.blocks);
+    while (true) {
+        if (ca < block->used_length && ca <= ha) {
+            ca = migration_bitmap_find_and_reset_dirty(block->mr, ca);
+            if (ca < block->used_length) {
+                got_ca = 1;
+            }
+        }
+        if (ha < block->used_length && ha <= ca) {
+            ha = host_bitmap_find_and_reset_dirty(block->mr, ha);
+            if (ha < block->used_length && ha != ca) {
+                got_ha = 1;
+            }
+            host_dirty += (ha < block->used_length ? 1 : 0);
+            both_dirty += (ha < block->used_length && ha == ca ? 1 : 0);
+        }
+        if (ca >= block->used_length && ha >= block->used_length) {
+            ca = 0;
+            ha = 0;
+            block = QLIST_NEXT_RCU(block, next);
+            if (!block) {
+                break;
+            }
+        } else {
+            if (got_ha) {
+                got_ha = 0;
+                dst_host = memory_region_get_ram_ptr(block->mr) + ha;
+                src_host = memory_region_get_ram_cache_ptr(block->mr, block)
+                           + ha;
+                memcpy(dst_host, src_host, TARGET_PAGE_SIZE);
+            }
+            if (got_ca) {
+                got_ca = 0;
+                dst_host = memory_region_get_ram_ptr(block->mr) + ca;
+                src_host = memory_region_get_ram_cache_ptr(block->mr, block)
+                           + ca;
+                memcpy(dst_host, src_host, TARGET_PAGE_SIZE);
+            }
+        }
+    }
+    rcu_read_unlock();
+    assert(migration_dirty_pages == 0);
+}
+
 static SaveVMHandlers savevm_ram_handlers = {
     .save_live_setup = ram_save_setup,
     .save_live_iterate = ram_save_iterate,
diff --git a/include/migration/migration-colo.h b/include/migration/migration-colo.h
index d47ad72..7e177f8 100644
--- a/include/migration/migration-colo.h
+++ b/include/migration/migration-colo.h
@@ -37,5 +37,6 @@ void *colo_process_incoming_checkpoints(void *opaque);
 bool loadvm_in_colo_state(void);
 /* ram cache */
 void create_and_init_ram_cache(void);
+void colo_flush_ram_cache(void);
 void release_ram_cache(void);
 #endif
diff --git a/migration/colo.c b/migration/colo.c
index 119e66c..386f5f5 100644
--- a/migration/colo.c
+++ b/migration/colo.c
@@ -409,7 +409,6 @@ void *colo_process_incoming_checkpoints(void *opaque)
         }
         DPRINTF("Finish load all vm state to cache\n");
         qemu_mutex_unlock_iothread();
-        /* TODO: flush vm state */
 
         ret = colo_ctl_put(ctl, COLO_CHECKPOINT_LOADED);
         if (ret < 0) {
-- 
1.7.12.4