[Qemu-devel] [PATCH 2/2] hostmem-file: allow option 'size' optional

[Haozhong Zhang]

If 'size' option of hostmem-file is not given, QEMU will use the file
size of 'mem-path' instead. For an empty file, a non-zero size must be
specified by the option 'size'.

Signed-off-by: Haozhong Zhang <address@hidden>
---
 backends/hostmem-file.c | 10 ++++++----
 exec.c                  |  8 ++++++++
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index 42efb2f..f94d2f7 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -40,10 +40,6 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error 
**errp)
 {
     HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(backend);
 
-    if (!backend->size) {
-        error_setg(errp, "can't create backend with size 0");
-        return;
-    }
     if (!fb->mem_path) {
         error_setg(errp, "mem-path property not set");
         return;
@@ -62,6 +58,12 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error 
**errp)
         g_free(path);
     }
 #endif
+    if (!errp && !backend->size) {
+        backend->size = memory_region_size(&backend->mr);
+        if (!backend->size) {
+            error_setg(errp, "can't create backend with size 0");
+        }
+    }
 }
 
 static char *get_mem_path(Object *o, Error **errp)
diff --git a/exec.c b/exec.c
index 95983c9..91adc62 100644
--- a/exec.c
+++ b/exec.c
@@ -1274,6 +1274,14 @@ static void *file_ram_alloc(RAMBlock *block,
         goto error;
     }
 
+    if (memory) {
+        memory = memory ?: file_size;
+        memory_region_set_size(block->mr, memory);
+        memory = HOST_PAGE_ALIGN(memory);
+        block->used_length = memory;
+        block->max_length = memory;
+    }
+
     if (memory < block->page_size) {
         error_setg(errp, "memory size 0x" RAM_ADDR_FMT " must be equal to "
                    "or larger than page size 0x%zx",
-- 
2.10.1