[PATCH V1 09/32] savevm: prevent cprsave if memory is volatile

[Steve Sistare <steven.sistare@oracle.com>]

cprsave and cprload require that guest ram be backed by an externally
visible shared file.  Check that in cprsave.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
---
 exec.c                | 32 ++++++++++++++++++++++++++++++++
 include/exec/memory.h |  2 ++
 migration/savevm.c    |  4 ++++
 3 files changed, 38 insertions(+)

diff --git a/exec.c b/exec.c
index 6f381f9..02160e0 100644
--- a/exec.c
+++ b/exec.c
@@ -2726,6 +2726,38 @@ ram_addr_t qemu_ram_addr_from_host(void *ptr)
     return block->offset + offset;
 }
 
+/*
+ * Return true if any memory regions are writable and not backed by shared
+ * memory.  Exclude x86 option rom shadow "pc.rom" by name, even though it is
+ * writable.
+ */
+bool qemu_ram_volatile(Error **errp)
+{
+    RAMBlock *block;
+    MemoryRegion *mr;
+    bool ret = false;
+
+    rcu_read_lock();
+    QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
+        mr = block->mr;
+        if (mr &&
+            memory_region_is_ram(mr) &&
+            !memory_region_is_ram_device(mr) &&
+            !memory_region_is_rom(mr) &&
+            (!mr->name || strcmp(mr->name, "pc.rom")) &&
+            (block->fd == -1 || !qemu_ram_is_shared(block))) {
+
+            error_setg(errp, "Memory region %s is volatile",
+                       memory_region_name(mr));
+            ret = true;
+            break;
+        }
+    }
+
+    rcu_read_unlock();
+    return ret;
+}
+
 /* Generate a debug exception if a watchpoint has been hit.  */
 void cpu_check_watchpoint(CPUState *cpu, vaddr addr, vaddr len,
                           MemTxAttrs attrs, int flags, uintptr_t ra)
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 307e527..6aafbb0 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -2519,6 +2519,8 @@ bool ram_block_discard_is_disabled(void);
  */
 bool ram_block_discard_is_required(void);
 
+bool qemu_ram_volatile(Error **errp);
+
 #endif
 
 #endif
diff --git a/migration/savevm.c b/migration/savevm.c
index 1509173..f101039 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2713,6 +2713,10 @@ void save_cpr_snapshot(const char *file, const char *mode, Error **errp)
         return;
     }
 
+    if (op == VMS_REBOOT && qemu_ram_volatile(errp)) {
+        return;
+    }
+
     f = qf_file_open(file, O_CREAT | O_WRONLY | O_TRUNC, 0600, errp);
     if (!f) {
         return;
-- 
1.8.3.1