[Qemu-devel] [PATCH for-2.13] Add host_memory_backend_pagesize() helper

[David Gibson <david@gibson.dropbear.id.au>]

There are a couple places (one generic, one target specific) where we need
to get the host page size associated with a particular memory backend.  I
have some upcoming code which will add another place which wants this.  So,
for convenience, add a helper function to calculate this.

host_memory_backend_pagesize() returns the host pagesize for a given
HostMemoryBackend object, or for the default backend (-mem-path) if passed
NULL.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 backends/hostmem.c       | 20 ++++++++++++++++++++
 exec.c                   | 21 +++++----------------
 include/sysemu/hostmem.h |  2 ++
 target/ppc/kvm.c         | 10 +---------
 4 files changed, 28 insertions(+), 25 deletions(-)

diff --git a/backends/hostmem.c b/backends/hostmem.c
index f61093654e..b6a60cfc5d 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -18,6 +18,7 @@
 #include "qapi/visitor.h"
 #include "qemu/config-file.h"
 #include "qom/object_interfaces.h"
+#include "qemu/mmap-alloc.h"
 
 #ifdef CONFIG_NUMA
 #include <numaif.h>
@@ -262,6 +263,25 @@ bool host_memory_backend_is_mapped(HostMemoryBackend *backend)
     return backend->is_mapped;
 }
 
+long host_memory_backend_pagesize(HostMemoryBackend *memdev)
+{
+    const char *path = NULL;
+
+#ifdef __linux__
+    if (memdev) {
+        path = object_property_get_str(OBJECT(memdev), "mem-path", NULL);
+    } else {
+        path = mem_path;
+    }
+#endif
+
+    if (path) {
+        return qemu_mempath_getpagesize(path);
+    } else {
+        return getpagesize();
+    }
+}
+
 static void
 host_memory_backend_memory_complete(UserCreatable *uc, Error **errp)
 {
diff --git a/exec.c b/exec.c
index c09bd93df3..04856c2402 100644
--- a/exec.c
+++ b/exec.c
@@ -1488,18 +1488,13 @@ void ram_block_dump(Monitor *mon)
  */
 static int find_max_supported_pagesize(Object *obj, void *opaque)
 {
-    char *mem_path;
     long *hpsize_min = opaque;
 
     if (object_dynamic_cast(obj, TYPE_MEMORY_BACKEND)) {
-        mem_path = object_property_get_str(obj, "mem-path", NULL);
-        if (mem_path) {
-            long hpsize = qemu_mempath_getpagesize(mem_path);
-            if (hpsize < *hpsize_min) {
-                *hpsize_min = hpsize;
-            }
-        } else {
-            *hpsize_min = getpagesize();
+        long hpsize = host_memory_backend_pagesize(MEMORY_BACKEND(obj));
+
+        if (hpsize < *hpsize_min) {
+            *hpsize_min = hpsize;
         }
     }
 
@@ -1509,15 +1504,9 @@ static int find_max_supported_pagesize(Object *obj, void *opaque)
 long qemu_getrampagesize(void)
 {
     long hpsize = LONG_MAX;
-    long mainrampagesize;
+    long mainrampagesize = host_memory_backend_pagesize(NULL);
     Object *memdev_root;
 
-    if (mem_path) {
-        mainrampagesize = qemu_mempath_getpagesize(mem_path);
-    } else {
-        mainrampagesize = getpagesize();
-    }
-
     /* it's possible we have memory-backend objects with
      * hugepage-backed RAM. these may get mapped into system
      * address space via -numa parameters or memory hotplug
diff --git a/include/sysemu/hostmem.h b/include/sysemu/hostmem.h
index 47bc9846ac..f474ef97f6 100644
--- a/include/sysemu/hostmem.h
+++ b/include/sysemu/hostmem.h
@@ -68,4 +68,6 @@ 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);
+long host_memory_backend_pagesize(HostMemoryBackend *memdev);
+
 #endif
diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
index b329cd8173..0adcf18c9f 100644
--- a/target/ppc/kvm.c
+++ b/target/ppc/kvm.c
@@ -493,15 +493,7 @@ static void kvm_fixup_page_sizes(PowerPCCPU *cpu)
 bool kvmppc_is_mem_backend_page_size_ok(const char *obj_path)
 {
     Object *mem_obj = object_resolve_path(obj_path, NULL);
-    char *mempath = object_property_get_str(mem_obj, "mem-path", NULL);
-    long pagesize;
-
-    if (mempath) {
-        pagesize = qemu_mempath_getpagesize(mempath);
-        g_free(mempath);
-    } else {
-        pagesize = getpagesize();
-    }
+    long pagesize = host_memory_backend_pagesize(MEMORY_BACKEND(mem_obj));
 
     return pagesize >= max_cpu_page_size;
 }
-- 
2.14.3