hostmem: add property to map memory with MAP_SHARED
A new "share" property can be used with the "memory-file" backend to
map memory with MAP_SHARED instead of MAP_PRIVATE.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
diff --git a/exec.c b/exec.c
index a27923a..1ca7bac 100644
--- a/exec.c
+++ b/exec.c
@@ -73,6 +73,9 @@
/* RAM is pre-allocated and passed into qemu_ram_alloc_from_ptr */
#define RAM_PREALLOC (1 << 0)
+/* RAM is mmap-ed with MAP_SHARED */
+#define RAM_SHARED (1 << 1)
+
#endif
struct CPUTailQ cpus = QTAILQ_HEAD_INITIALIZER(cpus);
@@ -1074,7 +1077,9 @@
perror("ftruncate");
}
- area = mmap(0, memory, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
+ area = mmap(0, memory, PROT_READ | PROT_WRITE,
+ (block->flags & RAM_SHARED ? MAP_SHARED : MAP_PRIVATE),
+ fd, 0);
if (area == MAP_FAILED) {
error_setg_errno(errp, errno,
"unable to map backing store for hugepages");
@@ -1286,7 +1291,7 @@
#ifdef __linux__
ram_addr_t qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr,
- const char *mem_path,
+ bool share, const char *mem_path,
Error **errp)
{
RAMBlock *new_block;
@@ -1311,6 +1316,7 @@
new_block = g_malloc0(sizeof(*new_block));
new_block->mr = mr;
new_block->length = size;
+ new_block->flags = share ? RAM_SHARED : 0;
new_block->host = file_ram_alloc(new_block, size,
mem_path, errp);
if (!new_block->host) {
@@ -1413,12 +1419,8 @@
flags = MAP_FIXED;
munmap(vaddr, length);
if (block->fd >= 0) {
-#ifdef MAP_POPULATE
- flags |= mem_prealloc ? MAP_POPULATE | MAP_SHARED :
- MAP_PRIVATE;
-#else
- flags |= MAP_PRIVATE;
-#endif
+ flags |= (block->flags & RAM_SHARED ?
+ MAP_SHARED : MAP_PRIVATE);
area = mmap(vaddr, length, PROT_READ | PROT_WRITE,
flags, block->fd, offset);
} else {