[Qemu-devel] [PATCH RFC for-2.3 5/6] qga: implement qmp_guest_get_memory_block_size() for Linux with sysfs

[zhanghailiang <zhang.zhanghailiang@huawei.com>]

The size of a memory block is architecture dependent,
For example, power uses 16MiB, ia64 uses 1GiB, x86 uses 128M.
It represents the logical unit upon which memory online/offline operations are
to be performed.

This function will return the value to host user.

Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
---
 qga/commands-posix.c | 43 +++++++++++++++++++++++++++++++++++++------
 1 file changed, 37 insertions(+), 6 deletions(-)

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index 1010e86..02c6b44 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -2087,6 +2087,37 @@ int64_t qmp_guest_set_memory_blocks(GuestMemoryBlockList *mem_blks,
     return processed;
 }
 
+int64_t qmp_guest_get_memory_block_size(Error **errp)
+{
+    Error *local_err = NULL;
+    char *dirpath;
+    int dirfd;
+    char *buf;
+    int64_t block_size;
+
+    dirpath = g_strdup_printf("/sys/devices/system/memory/");
+    dirfd = open(dirpath, O_RDONLY | O_DIRECTORY);
+    if (dirfd == -1) {
+        error_setg_errno(errp, errno, "open(\"%s\")", dirpath);
+        g_free(dirpath);
+        return -1;
+    }
+    g_free(dirpath);
+
+    buf = g_malloc0(20);
+    ga_read_sysfs_file(dirfd, "block_size_bytes", buf, 20, &local_err);
+    if (local_err) {
+        g_free(buf);
+        error_propagate(errp, local_err);
+        return -1;
+    }
+
+    block_size = strtol(buf, NULL, 16); /* the unit is bytes */
+    g_free(buf);
+
+    return block_size;
+}
+
 #else /* defined(__linux__) */
 
 void qmp_guest_suspend_disk(Error **errp)
@@ -2135,6 +2166,12 @@ int64_t qmp_guest_set_memory_blocks(GuestMemoryBlockList *mem_blks,
     return -1;
 }
 
+int64_t qmp_guest_get_memory_block_size(Error **errp)
+{
+    error_set(errp, QERR_UNSUPPORTED);
+    return -1;
+}
+
 #endif
 
 #if !defined(CONFIG_FSFREEZE)
@@ -2221,12 +2258,6 @@ GList *ga_command_blacklist_init(GList *blacklist)
     return blacklist;
 }
 
-int64_t qmp_guest_get_memory_block_size(Error **errp)
-{
-    error_set(errp, QERR_UNSUPPORTED);
-    return -1;
-}
-
 /* register init/cleanup routines for stateful command groups */
 void ga_command_state_init(GAState *s, GACommandState *cs)
 {
-- 
1.7.12.4