[libvirt] [PATCH] util:qemu: fix IOThreadinfo always get failed when get running vm status

[Luyao Huang]

When we use iothreadinfo to get iothread information, we will get
error like this:

 # virsh iothreadinfo rhel7.0 --live
 error: Unable to get domain IOThreads information
 error: Unable to encode message payload

This is because virProcessGetAffinity() return a bitmap which map_len
is too big to send via rpc:

 (gdb) p *map
 $7 = {max_bit = 262144, map_len = 4096, map = 0x7f9b6c2c0a20}

To fix this issue add a new parameter &maxcpu to virProcessGetAffinity()
to let callers specify the maxcpu (also in most machine, no need loop
262144 times to check if cpu is set), if set &maxcpu to zero,
virProcessGetAffinity() will use default value (262144 or 1024) to
create bitmap. This issue was introduced in commit 825df8c.

Signed-off-by: Luyao Huang <lhuang at redhat.com>
---
 src/qemu/qemu_driver.c | 4 ++--
 src/util/virprocess.c  | 7 ++++---
 src/util/virprocess.h  | 2 +-
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 2b530c8..e1ad696 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -1459,7 +1459,7 @@ qemuDomainHelperGetVcpus(virDomainObjPtr vm, virVcpuInfoPtr info, int maxinfo,
                 unsigned char *cpumap = VIR_GET_CPUMAP(cpumaps, maplen, v);
                 virBitmapPtr map = NULL;
 
-                if (!(map = virProcessGetAffinity(priv->vcpupids[v])))
+                if (!(map = virProcessGetAffinity(priv->vcpupids[v], hostcpus)))
                     return -1;
 
                 virBitmapToDataBuf(map, cpumap, maplen);
@@ -5619,7 +5619,7 @@ qemuDomainGetIOThreadsLive(virQEMUDriverPtr driver,
             goto endjob;
         info_ret[i]->iothread_id = iothreads[i]->iothread_id;
 
-        if (!(map = virProcessGetAffinity(iothreads[i]->thread_id)))
+        if (!(map = virProcessGetAffinity(iothreads[i]->thread_id, hostcpus)))
             goto endjob;
 
         if (virBitmapToData(map, &info_ret[i]->cpumap,
diff --git a/src/util/virprocess.c b/src/util/virprocess.c
index 8fa7a9b..8800623 100644
--- a/src/util/virprocess.c
+++ b/src/util/virprocess.c
@@ -469,7 +469,8 @@ int virProcessSetAffinity(pid_t pid, virBitmapPtr map)
 }
 
 virBitmapPtr
-virProcessGetAffinity(pid_t pid)
+virProcessGetAffinity(pid_t pid,
+                      int maxcpu)
 {
     size_t i;
     cpu_set_t *mask;
@@ -504,10 +505,10 @@ virProcessGetAffinity(pid_t pid)
         goto cleanup;
     }
 
-    if (!(ret = virBitmapNew(ncpus)))
+    if (!(ret = virBitmapNew(maxcpu ? maxcpu : ncpus)))
           goto cleanup;
 
-    for (i = 0; i < ncpus; i++) {
+    for (i = 0; i < (maxcpu ? maxcpu : ncpus); i++) {
 # ifdef CPU_ALLOC
          /* coverity[overrun-local] */
         if (CPU_ISSET_S(i, masklen, mask))
diff --git a/src/util/virprocess.h b/src/util/virprocess.h
index 1768009..cc903ac 100644
--- a/src/util/virprocess.h
+++ b/src/util/virprocess.h
@@ -58,7 +58,7 @@ int virProcessKillPainfully(pid_t pid, bool force);
 
 int virProcessSetAffinity(pid_t pid, virBitmapPtr map);
 
-virBitmapPtr virProcessGetAffinity(pid_t pid);
+virBitmapPtr virProcessGetAffinity(pid_t pid, int maxcpu);
 
 int virProcessGetPids(pid_t pid, size_t *npids, pid_t **pids);
 
-- 
1.8.3.1