[Qemu-devel] [PATCH 0/2] hostmem: introduce host_memory_backend_mr_inited

[Qemu-devel] [PATCH 0/2] hostmem: introduce host_memory_backend_mr_inited

[Peter Xu]

This is a tiny cleanup series for host backend mem. Patch 1 introduced
the new interface, patch 2 uses them. Please review, thanks.

Peter Xu (2):
  hostmem: introduce host_memory_backend_mr_inited()
  hostmem: use host_memory_backend_mr_inited() where proper

 backends/hostmem-file.c  |  6 +++---
 backends/hostmem.c       | 19 ++++++++++++++-----
 include/sysemu/hostmem.h |  1 +
 3 files changed, 18 insertions(+), 8 deletions(-)

-- 
2.7.4

[Qemu-devel] [PATCH 1/2] hostmem: introduce host_memory_backend_mr_inited()

[Peter Xu]

We were checking this against memory region size of host memory
backend's mr field to see whether the mr has been inited. This is
efficient but less elegant. Let's make a helper for it to avoid
confusions, along with some notes.

Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 backends/hostmem.c       | 9 +++++++++
 include/sysemu/hostmem.h | 1 +
 2 files changed, 10 insertions(+)

diff --git a/backends/hostmem.c b/backends/hostmem.c
index 7f5de70..4e9ef62 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -243,6 +243,15 @@ static void host_memory_backend_init(Object *obj)
     backend->prealloc = mem_prealloc;
 }
 
+bool host_memory_backend_mr_inited(HostMemoryBackend *backend)
+{
+    /*
+     * NOTE: We forbid zero-length memory backend, so here zero means
+     * "we haven't inited the backend memory region yet".
+     */
+    return memory_region_size(&backend->mr) != 0;
+}
+
 MemoryRegion *
 host_memory_backend_get_memory(HostMemoryBackend *backend, Error **errp)
 {
diff --git a/include/sysemu/hostmem.h b/include/sysemu/hostmem.h
index ecae0cf..ed6a437 100644
--- a/include/sysemu/hostmem.h
+++ b/include/sysemu/hostmem.h
@@ -62,6 +62,7 @@ struct HostMemoryBackend {
     MemoryRegion mr;
 };
 
+bool host_memory_backend_mr_inited(HostMemoryBackend *backend);
 MemoryRegion *host_memory_backend_get_memory(HostMemoryBackend *backend,
                                              Error **errp);
 
-- 
2.7.4

[Qemu-devel] [PATCH 2/2] hostmem: use host_memory_backend_mr_inited() where proper

[Peter Xu]

Use the new interface to boost readability.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 backends/hostmem-file.c |  6 +++---
 backends/hostmem.c      | 10 +++++-----
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index 42efb2f..fc4ef46 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -51,7 +51,7 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
 #ifndef CONFIG_LINUX
     error_setg(errp, "-mem-path not supported on this host");
 #else
-    if (!memory_region_size(&backend->mr)) {
+    if (!host_memory_backend_mr_inited(backend)) {
         gchar *path;
         backend->force_prealloc = mem_prealloc;
         path = object_get_canonical_path(OBJECT(backend));
@@ -76,7 +76,7 @@ static void set_mem_path(Object *o, const char *str, Error **errp)
     HostMemoryBackend *backend = MEMORY_BACKEND(o);
     HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o);
 
-    if (memory_region_size(&backend->mr)) {
+    if (host_memory_backend_mr_inited(backend)) {
         error_setg(errp, "cannot change property value");
         return;
     }
@@ -96,7 +96,7 @@ static void file_memory_backend_set_share(Object *o, bool value, Error **errp)
     HostMemoryBackend *backend = MEMORY_BACKEND(o);
     HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o);
 
-    if (memory_region_size(&backend->mr)) {
+    if (host_memory_backend_mr_inited(backend)) {
         error_setg(errp, "cannot change property value");
         return;
     }
diff --git a/backends/hostmem.c b/backends/hostmem.c
index 4e9ef62..07137a2 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -45,7 +45,7 @@ host_memory_backend_set_size(Object *obj, Visitor *v, const char *name,
     Error *local_err = NULL;
     uint64_t value;
 
-    if (memory_region_size(&backend->mr)) {
+    if (host_memory_backend_mr_inited(backend)) {
         error_setg(&local_err, "cannot change property value");
         goto out;
     }
@@ -152,7 +152,7 @@ static void host_memory_backend_set_merge(Object *obj, bool value, Error **errp)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);
 
-    if (!memory_region_size(&backend->mr)) {
+    if (!host_memory_backend_mr_inited(backend)) {
         backend->merge = value;
         return;
     }
@@ -178,7 +178,7 @@ static void host_memory_backend_set_dump(Object *obj, bool value, Error **errp)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);
 
-    if (!memory_region_size(&backend->mr)) {
+    if (!host_memory_backend_mr_inited(backend)) {
         backend->dump = value;
         return;
     }
@@ -214,7 +214,7 @@ static void host_memory_backend_set_prealloc(Object *obj, bool value,
         }
     }
 
-    if (!memory_region_size(&backend->mr)) {
+    if (!host_memory_backend_mr_inited(backend)) {
         backend->prealloc = value;
         return;
     }
@@ -255,7 +255,7 @@ bool host_memory_backend_mr_inited(HostMemoryBackend *backend)
 MemoryRegion *
 host_memory_backend_get_memory(HostMemoryBackend *backend, Error **errp)
 {
-    return memory_region_size(&backend->mr) ? &backend->mr : NULL;
+    return host_memory_backend_mr_inited(backend) ? &backend->mr : NULL;
 }
 
 void host_memory_backend_set_mapped(HostMemoryBackend *backend, bool mapped)
-- 
2.7.4

Re: [Qemu-devel] [PATCH 0/2] hostmem: introduce host_memory_backend_mr_inited

[Eduardo Habkost]

On Fri, Mar 10, 2017 at 09:09:28PM +0800, Peter Xu wrote:
> This is a tiny cleanup series for host backend mem. Patch 1 introduced
> the new interface, patch 2 uses them. Please review, thanks.

Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>

Queueing for 2.10, on my machine-next branch.

-- 
Eduardo