[Qemu-devel] [RFC v7 01/16] exec.c: Add new exclusive bitmap to ram_list

[Alvise Rigo <a.rigo@virtualopensystems.com>]

The purpose of this new bitmap is to flag the memory pages that are in
the middle of LL/SC operations (after a LL, before a SC). For all these
pages, the corresponding TLB entries will be generated in such a way to
force the slow-path for all the VCPUs (see the following patches).

When the system starts, the whole memory is set to dirty.

Suggested-by: Jani Kokkonen <jani.kokkonen@huawei.com>
Suggested-by: Claudio Fontana <claudio.fontana@huawei.com>
Signed-off-by: Alvise Rigo <a.rigo@virtualopensystems.com>
---
 exec.c                  |  7 +++++--
 include/exec/memory.h   |  3 ++-
 include/exec/ram_addr.h | 31 +++++++++++++++++++++++++++++++
 3 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/exec.c b/exec.c
index 7115403..51f366d 100644
--- a/exec.c
+++ b/exec.c
@@ -1575,11 +1575,14 @@ static ram_addr_t ram_block_add(RAMBlock *new_block, Error **errp)
         int i;
 
         /* ram_list.dirty_memory[] is protected by the iothread lock.  */
-        for (i = 0; i < DIRTY_MEMORY_NUM; i++) {
+        for (i = 0; i < DIRTY_MEMORY_EXCLUSIVE; i++) {
             ram_list.dirty_memory[i] =
                 bitmap_zero_extend(ram_list.dirty_memory[i],
                                    old_ram_size, new_ram_size);
-       }
+        }
+        ram_list.dirty_memory[DIRTY_MEMORY_EXCLUSIVE] =
+            bitmap_zero_extend(ram_list.dirty_memory[DIRTY_MEMORY_EXCLUSIVE],
+                               old_ram_size, new_ram_size);
     }
     cpu_physical_memory_set_dirty_range(new_block->offset,
                                         new_block->used_length,
diff --git a/include/exec/memory.h b/include/exec/memory.h
index c92734a..71e0480 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -19,7 +19,8 @@
 #define DIRTY_MEMORY_VGA       0
 #define DIRTY_MEMORY_CODE      1
 #define DIRTY_MEMORY_MIGRATION 2
-#define DIRTY_MEMORY_NUM       3        /* num of dirty bits */
+#define DIRTY_MEMORY_EXCLUSIVE 3
+#define DIRTY_MEMORY_NUM       4        /* num of dirty bits */
 
 #include <stdint.h>
 #include <stdbool.h>
diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
index ef1489d..19789fc 100644
--- a/include/exec/ram_addr.h
+++ b/include/exec/ram_addr.h
@@ -21,6 +21,7 @@
 
 #ifndef CONFIG_USER_ONLY
 #include "hw/xen/xen.h"
+#include "sysemu/sysemu.h"
 
 struct RAMBlock {
     struct rcu_head rcu;
@@ -172,6 +173,9 @@ static inline void cpu_physical_memory_set_dirty_range(ram_addr_t start,
     if (unlikely(mask & (1 << DIRTY_MEMORY_CODE))) {
         bitmap_set_atomic(d[DIRTY_MEMORY_CODE], page, end - page);
     }
+    if (unlikely(mask & (1 << DIRTY_MEMORY_EXCLUSIVE))) {
+        bitmap_set_atomic(d[DIRTY_MEMORY_EXCLUSIVE], page, end - page);
+    }
     xen_modified_memory(start, length);
 }
 
@@ -287,5 +291,32 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(unsigned long *dest,
 }
 
 void migration_bitmap_extend(ram_addr_t old, ram_addr_t new);
+
+/* Exclusive bitmap support. */
+#define EXCL_BITMAP_GET_OFFSET(addr) (addr >> TARGET_PAGE_BITS)
+
+/* Make the page of @addr not exclusive. */
+static inline void cpu_physical_memory_unset_excl(ram_addr_t addr)
+{
+    set_bit_atomic(EXCL_BITMAP_GET_OFFSET(addr),
+                   ram_list.dirty_memory[DIRTY_MEMORY_EXCLUSIVE]);
+}
+
+/* Return true if the page of @addr is exclusive, i.e. the EXCL bit is set. */
+static inline int cpu_physical_memory_is_excl(ram_addr_t addr)
+{
+    return !test_bit(EXCL_BITMAP_GET_OFFSET(addr),
+                     ram_list.dirty_memory[DIRTY_MEMORY_EXCLUSIVE]);
+}
+
+/* Set the page of @addr as exclusive clearing its EXCL bit and return the
+ * previous bit's state. */
+static inline int cpu_physical_memory_set_excl(ram_addr_t addr)
+{
+    return bitmap_test_and_clear_atomic(
+                                ram_list.dirty_memory[DIRTY_MEMORY_EXCLUSIVE],
+                                EXCL_BITMAP_GET_OFFSET(addr), 1);
+}
+
 #endif
 #endif
-- 
2.7.0