[Qemu-devel] [PATCH RFC for-2.3 3/6] qga: implement qmp_guest_get_memory_blocks() for Linux with sysfs

[zhanghailiang]

We can get guest's memory block information by using command
"guest-get-memory-blocks", the returned value contains a list of memory block
info, such as phys_index, online state, can-offline info.

Signed-off-by: zhanghailiang <address@hidden>
---
 qga/commands-posix.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 60 insertions(+), 6 deletions(-)

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index 8917dca..d3f7d4f 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -2005,6 +2005,60 @@ static void transfer_memory_block(GuestMemoryBlock 
*mem_blk, bool sys2memblk,
     g_assert(res == 0);
 }
 
+GuestMemoryBlockList *qmp_guest_get_memory_blocks(Error **errp)
+{
+    GuestMemoryBlockList *head, **link;
+    Error *local_err = NULL;
+    struct dirent *de;
+    DIR *dp;
+
+    head = NULL;
+    link = &head;
+
+    dp = opendir("/sys/devices/system/memory/");
+    if (!dp) {
+        error_setg_errno(errp, errno, "Can't open directory"
+                         "\"/sys/devices/system/memory/\"\n");
+        return NULL;
+    }
+
+    /* Note: the phys_index of memory block may be discontinuous,
+     * this is because a memblk is the unit of the Sparse Memory design, which
+     * allows discontinuous memory ranges (ex. NUMA), so here we should
+     * traverse the memory block directory.
+     */
+    while ((de = readdir(dp)) != NULL) {
+        GuestMemoryBlock *mem_blk;
+        GuestMemoryBlockList *entry;
+
+        if ((strncmp(de->d_name, "memory", 6) != 0) ||
+            !(de->d_type & DT_DIR)) {
+            continue;
+        }
+
+        mem_blk = g_malloc0(sizeof *mem_blk);
+        /* The d_name is "memoryXXX",  phys_index is block id, same as XXX */
+        mem_blk->phys_index = strtoul(&de->d_name[6], NULL, 10);
+        mem_blk->has_can_offline = true; /* lolspeak ftw */
+        transfer_memory_block(mem_blk, true, &local_err);
+
+        entry = g_malloc0(sizeof *entry);
+        entry->value = mem_blk;
+
+        *link = entry;
+        link = &entry->next;
+    }
+
+    if (local_err == NULL) {
+        /* there's no guest with zero memroy blocks */
+        g_assert(head != NULL);
+        return head;
+    }
+
+    qapi_free_GuestMemoryBlockList(head);
+    error_propagate(errp, local_err);
+    return NULL;
+}
 #else /* defined(__linux__) */
 
 void qmp_guest_suspend_disk(Error **errp)
@@ -2040,6 +2094,12 @@ int64_t qmp_guest_set_vcpus(GuestLogicalProcessorList 
*vcpus, Error **errp)
     return -1;
 }
 
+GuestMemoryBlockList *qmp_guest_get_memory_blocks(Error **errp)
+{
+    error_set(errp, QERR_UNSUPPORTED);
+    return NULL;
+}
+
 #endif
 
 #if !defined(CONFIG_FSFREEZE)
@@ -2126,12 +2186,6 @@ GList *ga_command_blacklist_init(GList *blacklist)
     return blacklist;
 }
 
-GuestMemoryBlockList *qmp_guest_get_memory_blocks(Error **errp)
-{
-    error_set(errp, QERR_UNSUPPORTED);
-    return NULL;
-}
-
 int64_t qmp_guest_set_memory_blocks(GuestMemoryBlockList *mem_blks,
                                     Error **errp)
 {
-- 
1.7.12.4