[Qemu-devel] [PATCH v2 10/10] hostmem: use object id for memory region name with >= 3.1

["Marc-André Lureau" <marcandre.lureau@redhat.com>]

hostmem-file and hostmem-memfd use the whole object path for the
memory region name, and hostname-ram uses only the path component (the
object id, or canonical path basename):

qemu -m 1024 -object memory-backend-file,id=mem,size=1G,mem-path=/tmp/foo -numa node,memdev=mem -monitor stdio
(qemu) info ramblock
              Block Name    PSize              Offset               Used              Total
            /objects/mem    4 KiB  0x0000000000000000 0x0000000040000000 0x0000000040000000

qemu -m 1024 -object memory-backend-memfd,id=mem,size=1G -numa node,memdev=mem -monitor stdio
(qemu) info ramblock
              Block Name    PSize              Offset               Used              Total
            /objects/mem    4 KiB  0x0000000000000000 0x0000000040000000 0x0000000040000000

qemu -m 1024 -object memory-backend-ram,id=mem,size=1G -numa node,memdev=mem -monitor stdio
(qemu) info ramblock
              Block Name    PSize              Offset               Used              Total
                     mem    4 KiB  0x0000000000000000 0x0000000040000000 0x0000000040000000

Use the object id for -file and -memfd with >= 3.1 for consistency.
Having a consistent naming allow to migrate to different hostmem
backends.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 include/hw/compat.h      | 11 ++++++++++-
 include/sysemu/hostmem.h |  3 ++-
 backends/hostmem-file.c  |  8 ++++----
 backends/hostmem-memfd.c |  2 +-
 backends/hostmem-ram.c   |  9 ++++-----
 backends/hostmem.c       | 30 ++++++++++++++++++++++++++++++
 6 files changed, 51 insertions(+), 12 deletions(-)

diff --git a/include/hw/compat.h b/include/hw/compat.h
index 6f4d5fc647..60f4a939a7 100644
--- a/include/hw/compat.h
+++ b/include/hw/compat.h
@@ -2,7 +2,16 @@
 #define HW_COMPAT_H
 
 #define HW_COMPAT_3_0 \
-    /* empty */
+    {\
+        .driver   = "memory-backend-file",\
+        .property = "x-use-canonical-path-for-ramblock-id",\
+        .value    = "true",\
+    },\
+    {\
+        .driver   = "memory-backend-memfd",\
+        .property = "x-use-canonical-path-for-ramblock-id",\
+        .value    = "true",\
+    },
 
 #define HW_COMPAT_2_12 \
     {\
diff --git a/include/sysemu/hostmem.h b/include/sysemu/hostmem.h
index 6e6bd2c1cb..a023b372a4 100644
--- a/include/sysemu/hostmem.h
+++ b/include/sysemu/hostmem.h
@@ -53,7 +53,7 @@ struct HostMemoryBackend {
 
     /* protected */
     uint64_t size;
-    bool merge, dump;
+    bool merge, dump, use_canonical_path;
     bool prealloc, force_prealloc, is_mapped, share;
     DECLARE_BITMAP(host_nodes, MAX_NODES + 1);
     HostMemPolicy policy;
@@ -67,5 +67,6 @@ MemoryRegion *host_memory_backend_get_memory(HostMemoryBackend *backend);
 void host_memory_backend_set_mapped(HostMemoryBackend *backend, bool mapped);
 bool host_memory_backend_is_mapped(HostMemoryBackend *backend);
 size_t host_memory_backend_pagesize(HostMemoryBackend *memdev);
+char *host_memory_backend_get_name(HostMemoryBackend *backend);
 
 #endif
diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index 639c8d4307..c01a7cdf8d 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -55,16 +55,16 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
     error_setg(errp, "-mem-path not supported on this host");
 #else
     if (!host_memory_backend_mr_inited(backend)) {
-        gchar *path;
+        gchar *name;
         backend->force_prealloc = mem_prealloc;
-        path = object_get_canonical_path(OBJECT(backend));
+        name = host_memory_backend_get_name(backend);
         memory_region_init_ram_from_file(&backend->mr, OBJECT(backend),
-                                 path,
+                                 name,
                                  backend->size, fb->align,
                                  (backend->share ? RAM_SHARED : 0) |
                                  (fb->is_pmem ? RAM_PMEM : 0),
                                  fb->mem_path, errp);
-        g_free(path);
+        g_free(name);
     }
 #endif
 }
diff --git a/backends/hostmem-memfd.c b/backends/hostmem-memfd.c
index b6836b28e5..c5a4a9b530 100644
--- a/backends/hostmem-memfd.c
+++ b/backends/hostmem-memfd.c
@@ -57,7 +57,7 @@ memfd_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
         return;
     }
 
-    name = object_get_canonical_path(OBJECT(backend));
+    name = host_memory_backend_get_name(backend);
     memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend),
                                    name, backend->size, true, fd, errp);
     g_free(name);
diff --git a/backends/hostmem-ram.c b/backends/hostmem-ram.c
index 7ddd08d370..24b65d9ae3 100644
--- a/backends/hostmem-ram.c
+++ b/backends/hostmem-ram.c
@@ -16,21 +16,20 @@
 
 #define TYPE_MEMORY_BACKEND_RAM "memory-backend-ram"
 
-
 static void
 ram_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
 {
-    char *path;
+    char *name;
 
     if (!backend->size) {
         error_setg(errp, "can't create backend with size 0");
         return;
     }
 
-    path = object_get_canonical_path_component(OBJECT(backend));
-    memory_region_init_ram_shared_nomigrate(&backend->mr, OBJECT(backend), path,
+    name = host_memory_backend_get_name(backend);
+    memory_region_init_ram_shared_nomigrate(&backend->mr, OBJECT(backend), name,
                            backend->size, backend->share, errp);
-    g_free(path);
+    g_free(name);
 }
 
 static void
diff --git a/backends/hostmem.c b/backends/hostmem.c
index 1a89342039..0032232866 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -28,6 +28,16 @@ QEMU_BUILD_BUG_ON(HOST_MEM_POLICY_BIND != MPOL_BIND);
 QEMU_BUILD_BUG_ON(HOST_MEM_POLICY_INTERLEAVE != MPOL_INTERLEAVE);
 #endif
 
+char *
+host_memory_backend_get_name(HostMemoryBackend *self)
+{
+    if (!self->use_canonical_path) {
+        return object_get_canonical_path_component(OBJECT(self));
+    }
+
+    return object_get_canonical_path(OBJECT(self));
+}
+
 static void
 host_memory_backend_get_size(Object *obj, Visitor *v, const char *name,
                              void *opaque, Error **errp)
@@ -386,6 +396,23 @@ static void host_memory_backend_set_share(Object *o, bool value, Error **errp)
     backend->share = value;
 }
 
+static bool
+host_memory_backend_get_use_canonical_path(Object *obj, Error **errp)
+{
+    HostMemoryBackend *self = MEMORY_BACKEND(obj);
+
+    return self->use_canonical_path;
+}
+
+static void
+host_memory_backend_set_use_canonical_path(Object *obj, bool value,
+                                           Error **errp)
+{
+    HostMemoryBackend *self = MEMORY_BACKEND(obj);
+
+    self->use_canonical_path = value;
+}
+
 static void
 host_memory_backend_class_init(ObjectClass *oc, void *data)
 {
@@ -432,6 +459,9 @@ host_memory_backend_class_init(ObjectClass *oc, void *data)
         &error_abort);
     object_class_property_set_description(oc, "share",
         "Mark the memory as private to QEMU or shared", &error_abort);
+    object_class_property_add_bool(oc, "x-use-canonical-path-for-ramblock-id",
+        host_memory_backend_get_use_canonical_path,
+        host_memory_backend_set_use_canonical_path, &error_abort);
 }
 
 static const TypeInfo host_memory_backend_info = {
-- 
2.19.0.271.gfe8321ec05