[Qemu-devel] [PATCH 2/5] exec.c: use refcnt to protect device during dispatching

[Liu Ping Fan <qemulist@gmail.com>]

From: Liu Ping Fan <pingfank@linux.vnet.ibm.com>

acquire device's refcnt with qemu_device_tree_mutex rwlock, so we
can safely handle it when mmio dispatch.

If in radix-tree, leaf is subpage, then move further step to acquire
opaque which is the type --DeiveState.

Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
---
 exec.c   |   38 ++++++++++++++++++++++++++++++++++++++
 memory.h |    2 ++
 2 files changed, 40 insertions(+), 0 deletions(-)

diff --git a/exec.c b/exec.c
index 8244d54..d2a6d08 100644
--- a/exec.c
+++ b/exec.c
@@ -3032,6 +3032,30 @@ static void subpage_write(void *opaque, target_phys_addr_t addr,
     io_mem_write(section->mr, addr, value, len);
 }
 
+static MemoryRegionSection *subpage_get_backend(subpage_t *mmio,
+    target_phys_addr_t addr)
+{
+    MemoryRegionSection *section;
+    unsigned int idx = SUBPAGE_IDX(addr);
+
+    section = &phys_sections[mmio->sub_section[idx]];
+    return section;
+}
+
+void *get_backend(MemoryRegion* mr,  target_phys_addr_t addr)
+{
+    MemoryRegionSection *p;
+    Object *ret;
+
+    if (mr->subpage) {
+        p = subpage_get_backend(mr->opaque, addr);
+        ret = OBJECT(p->mr->opaque);
+    } else {
+        ret = OBJECT(mr->opaque);
+    }
+    return ret;
+}
+
 static const MemoryRegionOps subpage_ops = {
     .read = subpage_read,
     .write = subpage_write,
@@ -3396,13 +3420,25 @@ void cpu_physical_memory_rw(target_phys_addr_t addr, uint8_t *buf,
     uint32_t val;
     target_phys_addr_t page;
     MemoryRegionSection *section;
+    Object *bk;
 
     while (len > 0) {
         page = addr & TARGET_PAGE_MASK;
         l = (page + TARGET_PAGE_SIZE) - addr;
         if (l > len)
             l = len;
+
+        qemu_rwlock_rdlock_devtree();
         section = phys_page_find(page >> TARGET_PAGE_BITS);
+        if (!(memory_region_is_ram(section->mr) ||
+            memory_region_is_romd(section->mr)) && !is_write) {
+            bk = get_backend(section->mr, addr);
+            object_ref(bk);
+        } else if (!memory_region_is_ram(section->mr) && is_write) {
+            bk = get_backend(section->mr, addr);
+            object_ref(bk);
+        }
+        qemu_rwlock_unlock_devtree();
 
         if (is_write) {
             if (!memory_region_is_ram(section->mr)) {
@@ -3426,6 +3462,7 @@ void cpu_physical_memory_rw(target_phys_addr_t addr, uint8_t *buf,
                     io_mem_write(section->mr, addr1, val, 1);
                     l = 1;
                 }
+                object_unref(bk);
             } else if (!section->readonly) {
                 ram_addr_t addr1;
                 addr1 = memory_region_get_ram_addr(section->mr)
@@ -3464,6 +3501,7 @@ void cpu_physical_memory_rw(target_phys_addr_t addr, uint8_t *buf,
                     stb_p(buf, val);
                     l = 1;
                 }
+                object_unref(bk);
             } else {
                 /* RAM case */
                 ptr = qemu_get_ram_ptr(section->mr->ram_addr
diff --git a/memory.h b/memory.h
index 740c48e..e5a86dc 100644
--- a/memory.h
+++ b/memory.h
@@ -748,6 +748,8 @@ void memory_global_dirty_log_stop(void);
 
 void mtree_info(fprintf_function mon_printf, void *f);
 
+void *get_backend(MemoryRegion* mr,  target_phys_addr_t addr);
+
 #endif
 
 #endif
-- 
1.7.4.4