[Qemu-devel] [PATCH v6 4/6] Add support for marking memory to not be migrated. On migration, memory is checked for the NO_MIGRATION_FLAG.

[Cam Macdonell <cam@cs.ualberta.ca>]

This is useful for devices that do not want to take memory regions data with them on migration.
---
 arch_init.c  |   28 ++++++++++++++++------------
 cpu-all.h    |    2 ++
 cpu-common.h |    2 ++
 exec.c       |   12 ++++++++++++
 4 files changed, 32 insertions(+), 12 deletions(-)

diff --git a/arch_init.c b/arch_init.c
index cfc03ea..7a234fa 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -118,18 +118,21 @@ static int ram_save_block(QEMUFile *f)
                                             current_addr + TARGET_PAGE_SIZE,
                                             MIGRATION_DIRTY_FLAG);
 
-            p = qemu_get_ram_ptr(current_addr);
-
-            if (is_dup_page(p, *p)) {
-                qemu_put_be64(f, current_addr | RAM_SAVE_FLAG_COMPRESS);
-                qemu_put_byte(f, *p);
-            } else {
-                qemu_put_be64(f, current_addr | RAM_SAVE_FLAG_PAGE);
-                qemu_put_buffer(f, p, TARGET_PAGE_SIZE);
-            }
+            if (!cpu_physical_memory_get_dirty(current_addr,
+                                                    NO_MIGRATION_FLAG)) {
+                p = qemu_get_ram_ptr(current_addr);
+
+                if (is_dup_page(p, *p)) {
+                    qemu_put_be64(f, current_addr | RAM_SAVE_FLAG_COMPRESS);
+                    qemu_put_byte(f, *p);
+                } else {
+                    qemu_put_be64(f, current_addr | RAM_SAVE_FLAG_PAGE);
+                    qemu_put_buffer(f, p, TARGET_PAGE_SIZE);
+                }
 
-            found = 1;
-            break;
+                found = 1;
+                break;
+            }
         }
         addr += TARGET_PAGE_SIZE;
         current_addr = (saved_addr + addr) % last_ram_offset;
@@ -146,7 +149,8 @@ static ram_addr_t ram_save_remaining(void)
     ram_addr_t count = 0;
 
     for (addr = 0; addr < last_ram_offset; addr += TARGET_PAGE_SIZE) {
-        if (cpu_physical_memory_get_dirty(addr, MIGRATION_DIRTY_FLAG)) {
+        if (!cpu_physical_memory_get_dirty(addr, NO_MIGRATION_FLAG) &&
+                cpu_physical_memory_get_dirty(addr, MIGRATION_DIRTY_FLAG)) {
             count++;
         }
     }
diff --git a/cpu-all.h b/cpu-all.h
index 9080cc7..4df00ab 100644
--- a/cpu-all.h
+++ b/cpu-all.h
@@ -887,6 +887,8 @@ extern int mem_prealloc;
 #define CODE_DIRTY_FLAG      0x02
 #define MIGRATION_DIRTY_FLAG 0x08
 
+#define NO_MIGRATION_FLAG 0x10
+
 #define DIRTY_ALL_FLAG  (VGA_DIRTY_FLAG | CODE_DIRTY_FLAG | MIGRATION_DIRTY_FLAG)
 
 /* read dirty bit (return 0 or 1) */
diff --git a/cpu-common.h b/cpu-common.h
index 4b0ba60..a1ebbbe 100644
--- a/cpu-common.h
+++ b/cpu-common.h
@@ -39,6 +39,8 @@ static inline void cpu_register_physical_memory(target_phys_addr_t start_addr,
     cpu_register_physical_memory_offset(start_addr, size, phys_offset, 0);
 }
 
+void cpu_mark_pages_no_migrate(ram_addr_t start, uint64_t size);
+
 ram_addr_t cpu_get_physical_page_desc(target_phys_addr_t addr);
 ram_addr_t qemu_ram_map(ram_addr_t size, void *host);
 ram_addr_t qemu_ram_alloc(ram_addr_t);
diff --git a/exec.c b/exec.c
index 39c18a7..c11d22f 100644
--- a/exec.c
+++ b/exec.c
@@ -2786,6 +2786,18 @@ static void *file_ram_alloc(ram_addr_t memory, const char *path)
 }
 #endif
 
+void cpu_mark_pages_no_migrate(ram_addr_t start, uint64_t length)
+{
+    int i, len;
+    uint8_t *p;
+
+    len = length >> TARGET_PAGE_BITS;
+    p = phys_ram_flags + (start >> TARGET_PAGE_BITS);
+    for (i = 0; i < len; i++) {
+        p[i] |= NO_MIGRATION_FLAG;
+    }
+}
+
 ram_addr_t qemu_ram_map(ram_addr_t size, void *host)
 {
     RAMBlock *new_block;
-- 
1.6.3.2.198.g6096d