[libvirt] [PATCH 2/3] qemu: Re-detect virtual cpu threads after cpu hot (un)plug.

[Peter Krempa]

After a cpu hotplug the qemu driver did not refresh information about
virtual procesors used by qemu and their corresponding threads. This
patch forces a re-detection as is done on start of QEMU.

This ensures that correct informations are reported by the
virDomainGetVcpus API and "virsh vcpuinfo".
---
 src/qemu/qemu_driver.c |   24 ++++++++++++++++++++++++
 1 files changed, 24 insertions(+), 0 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 7b1d1b6..fcaf0d2 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -3343,6 +3343,8 @@ static int qemudDomainHotplugVcpus(struct qemud_driver *driver,
     int ret = -1;
     int oldvcpus = vm->def->vcpus;
     int vcpus = oldvcpus;
+    pid_t *cpupids = NULL;
+    int ncpupids;

     qemuDomainObjEnterMonitor(driver, vm);

@@ -3373,8 +3375,30 @@ static int qemudDomainHotplugVcpus(struct qemud_driver *driver,
         }
     }

+    /* after hotplugging the cpu we need to re-detect threads for the virtual
+     * cpus */
+    if ((ncpupids = qemuMonitorGetCPUInfo(priv->mon, &cpupids)) < 0)
+        goto cleanup;
+
     ret = 0;

+    /* Treat failure to get VCPU<->PID mapping as non-fatal */
+    if (ncpupids == 0)
+        goto cleanup;
+
+    if (ncpupids != vcpus) {
+        qemuReportError(VIR_ERR_INTERNAL_ERROR,
+                        _("got wrong number of vCPU pids from QEMU monitor. "
+                          "got %d, wanted %d"),
+                        ncpupids, vcpus);
+        VIR_FREE(cpupids);
+        ret = -1;
+        goto cleanup;
+    }
+
+    priv->nvcpupids = ncpupids;
+    priv->vcpupids = cpupids;
+
 cleanup:
     qemuDomainObjExitMonitor(driver, vm);
     vm->def->vcpus = vcpus;
-- 
1.7.3.4