[libvirt] [PATCH 6/6] qemu: Fix hotplugging cpus with strict memory pinning

[Martin Kletzander]

When hot-plugging a VCPU into the guest, kvm needs to allocate some data
from the DMA zone, which might be in a memory node that's not allowed in
cpuset.mems.  Basically the same problem as there was with starting the
domain and due to which commit 7e72ac787848b7434c9359a57c1e2789d92350f8
exists.  This patch just extends it to hotplugging as well.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1161540

Signed-off-by: Martin Kletzander <mkletzan at redhat.com>
---
 src/qemu/qemu_driver.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index bfa62c4..dbe48ad 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -97,6 +97,7 @@
 #include "virhostdev.h"
 #include "domain_capabilities.h"
 #include "vircgroup.h"
+#include "virnuma.h"

 #define VIR_FROM_THIS VIR_FROM_QEMU

@@ -4621,6 +4622,11 @@ qemuDomainSetVcpusFlags(virDomainPtr dom, unsigned int nvcpus,
     int ncpuinfo;
     qemuDomainObjPrivatePtr priv;
     size_t i;
+    virCgroupPtr cgroup_temp = NULL;
+    char *mem_mask = NULL;
+    char *all_nodes_str = NULL;
+    virBitmapPtr all_nodes = NULL;
+    virErrorPtr err = NULL;

     virCheckFlags(VIR_DOMAIN_AFFECT_LIVE |
                   VIR_DOMAIN_AFFECT_CONFIG |
@@ -4646,9 +4652,22 @@ qemuDomainSetVcpusFlags(virDomainPtr dom, unsigned int nvcpus,

     priv = vm->privateData;

+    if (virCgroupNewEmulator(priv->cgroup, false, &cgroup_temp) < 0)
+        goto cleanup;
+
+    if (!(all_nodes = virNumaGetHostNodeset()))
+        goto cleanup;
+
+    if (!(all_nodes_str = virBitmapFormat(all_nodes)))
+        goto cleanup;
+
     if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0)
         goto cleanup;

+    if (virCgroupGetCpusetMems(cgroup_temp, &mem_mask) < 0 ||
+        virCgroupSetCpusetMems(cgroup_temp, all_nodes_str) < 0)
+        goto endjob;
+
     maximum = (flags & VIR_DOMAIN_VCPU_MAXIMUM) != 0;
     flags &= ~VIR_DOMAIN_VCPU_MAXIMUM;

@@ -4758,6 +4777,12 @@ qemuDomainSetVcpusFlags(virDomainPtr dom, unsigned int nvcpus,
     ret = 0;

  endjob:
+    if (mem_mask) {
+        err = virSaveLastError();
+        virCgroupSetCpusetMems(cgroup_temp, mem_mask);
+        virSetError(err);
+    }
+
     if (!qemuDomainObjEndJob(driver, vm))
         vm = NULL;

@@ -4766,6 +4791,10 @@ qemuDomainSetVcpusFlags(virDomainPtr dom, unsigned int nvcpus,
         virObjectUnlock(vm);
     virObjectUnref(caps);
     VIR_FREE(cpuinfo);
+    VIR_FREE(mem_mask);
+    VIR_FREE(all_nodes_str);
+    virBitmapFree(all_nodes);
+    virCgroupFree(&cgroup_temp);
     virObjectUnref(cfg);
     return ret;
 }
-- 
2.2.0