memory: add error propagation to file-based RAM allocation

Right now, -mem-path will fall back to RAM-based allocation in some
cases.  This should never happen with "-object memory-file", prepare
the code by adding correct error propagation.

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>

MST: drop \n at end of error messages

exec.c

@@ -1016,7 +1016,8 @@ static long gethugepagesize(const char *path)
 
 static void *file_ram_alloc(RAMBlock *block,
                             ram_addr_t memory,
-                            const char *path)
+                            const char *path,
+                            Error **errp)
 {
     char *filename;
     char *sanitized_name;
@@ -1035,7 +1036,8 @@ static void *file_ram_alloc(RAMBlock *block,
     }
 
     if (kvm_enabled() && !kvm_has_sync_mmu()) {
-        fprintf(stderr, "host lacks kvm mmu notifiers, -mem-path unsupported\n");
+        error_setg(errp,
+                   "host lacks kvm mmu notifiers, -mem-path unsupported");
         goto error;
     }
 
@@ -1052,7 +1054,8 @@ static void *file_ram_alloc(RAMBlock *block,
 
     fd = mkstemp(filename);
     if (fd < 0) {
-        perror("unable to create backing store for hugepages");
+        error_setg_errno(errp, errno,
+                         "unable to create backing store for hugepages");
         g_free(filename);
         goto error;
     }
@@ -1067,12 +1070,14 @@ static void *file_ram_alloc(RAMBlock *block,
      * If anything goes wrong with it under other filesystems,
      * mmap will fail.
      */
-    if (ftruncate(fd, memory))
+    if (ftruncate(fd, memory)) {
         perror("ftruncate");
+    }
 
     area = mmap(0, memory, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
     if (area == MAP_FAILED) {
-        perror("file_ram_alloc: can't mmap RAM pages");
+        error_setg_errno(errp, errno,
+                         "unable to map backing store for hugepages");
         close(fd);
         goto error;
     }
@@ -1281,13 +1286,14 @@ static ram_addr_t ram_block_add(RAMBlock *new_block)
 
 #ifdef __linux__
 ram_addr_t qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr,
-                                    const char *mem_path)
+                                    const char *mem_path,
+                                    Error **errp)
 {
     RAMBlock *new_block;
 
     if (xen_enabled()) {
-        fprintf(stderr, "-mem-path not supported with Xen\n");
+        error_setg(errp, "-mem-path not supported with Xen");
-        exit(1);
+        return -1;
     }
 
     if (phys_mem_alloc != qemu_anon_ram_alloc) {
@@ -1296,16 +1302,22 @@ ram_addr_t qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr,
          * phys_mem_alloc, but we haven't bothered to provide
          * a hook there.
          */
-        fprintf(stderr,
+        error_setg(errp,
-                "-mem-path not supported with this accelerator\n");
+                   "-mem-path not supported with this accelerator");
-        exit(1);
+        return -1;
     }
 
     size = TARGET_PAGE_ALIGN(size);
     new_block = g_malloc0(sizeof(*new_block));
     new_block->mr = mr;
     new_block->length = size;
-    new_block->host = file_ram_alloc(new_block, size, mem_path);
+    new_block->host = file_ram_alloc(new_block, size,
+                                     mem_path, errp);
+    if (!new_block->host) {
+        g_free(new_block);
+        return -1;
+    }
+
     return ram_block_add(new_block);
 }
 #endif

include/exec/memory.h

@@ -31,6 +31,7 @@
 #include "qemu/queue.h"
 #include "qemu/int128.h"
 #include "qemu/notify.h"
+#include "qapi/error.h"
 
 #define MAX_PHYS_ADDR_SPACE_BITS 62
 #define MAX_PHYS_ADDR            (((hwaddr)1 << MAX_PHYS_ADDR_SPACE_BITS) - 1)
@@ -321,12 +322,14 @@ void memory_region_init_ram(MemoryRegion *mr,
  * @name: the name of the region.
  * @size: size of the region.
  * @path: the path in which to allocate the RAM.
+ * @errp: pointer to Error*, to store an error if it happens.
  */
 void memory_region_init_ram_from_file(MemoryRegion *mr,
                                       struct Object *owner,
                                       const char *name,
                                       uint64_t size,
-                                      const char *path);
+                                      const char *path,
+                                      Error **errp);
 #endif
 
 /**

include/exec/ram_addr.h

@@ -23,7 +23,7 @@
 #include "hw/xen/xen.h"
 
 ram_addr_t qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr,
-                                    const char *mem_path);
+                                    const char *mem_path, Error **errp);
 ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void *host,
                                    MemoryRegion *mr);
 ram_addr_t qemu_ram_alloc(ram_addr_t size, MemoryRegion *mr);

memory.c

@@ -1038,13 +1038,14 @@ void memory_region_init_ram_from_file(MemoryRegion *mr,
                                       struct Object *owner,
                                       const char *name,
                                       uint64_t size,
-                                      const char *path)
+                                      const char *path,
+                                      Error **errp)
 {
     memory_region_init(mr, owner, name, size);
     mr->ram = true;
     mr->terminates = true;
     mr->destructor = memory_region_destructor_ram;
-    mr->ram_addr = qemu_ram_alloc_from_file(size, mr, path);
+    mr->ram_addr = qemu_ram_alloc_from_file(size, mr, path, errp);
 }
 #endif
 

numa.c

@@ -230,7 +230,18 @@ static void allocate_system_memory_nonnuma(MemoryRegion *mr, Object *owner,
 {
     if (mem_path) {
 #ifdef __linux__
-        memory_region_init_ram_from_file(mr, owner, name, ram_size, mem_path);
+        Error *err = NULL;
+        memory_region_init_ram_from_file(mr, owner, name, ram_size,
+                                         mem_path, &err);
+
+        /* Legacy behavior: if allocation failed, fall back to
+         * regular RAM allocation.
+         */
+        if (!memory_region_size(mr)) {
+            qerror_report_err(err);
+            error_free(err);
+            memory_region_init_ram(mr, owner, name, ram_size);
+        }
 #else
         fprintf(stderr, "-mem-path not supported on this host\n");
         exit(1);