qemu: Don't report spurious errors from vCPU tid validation on hotunplug timeout

Use of qemuDomainValidateVcpuInfo in the helpers for hotplug and unplug
of vCPUs can lead to spurious errors reported such as:

  internal error: qemu didn't report thread id for vcpu 'XX'"

The reason for this is that qemuDomainValidateVcpuInfo validates the
state of all vCPUs against the expected state of vCPUs. If an unplug
operation completed before libvirt was unable to process it yet the
expected state could not reflect the current state.

To avoid spurious errors the qemuDomainHotplugAddVcpu and
qemuDomainRemoveVcpu functions are modified to do localized validation
only for the vCPUs they actually modify.

We also now ensure that the cgroups are modified before bailing out on
error for any vCPUs which passed validation.

Additionally in order for qemuDomainRemoveVcpuAlias to be able to find
the unplugged vCPU we must ensure that qemuDomainRefreshVcpuInfo does
not clear out the alias in case when the vCPU is no longer reported by
qemu.

Co-authored-by: Partha Satapathy <partha.satapathy@oracle.com>
Signed-off-by: Shaleen Bathla <shaleen.bathla@oracle.com>
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 8ae458ae45bfbcb2d2478bf7a489eddbf4249435..5d81dc7a45eee5f4dcb10f4b359bdeefb5e4bdab 100644 (file)
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -9799,8 +9799,10 @@ qemuDomainRefreshVcpuInfo(virDomainObj *vm,
         vcpupriv->vcpus = info[i].vcpus;
         VIR_FREE(vcpupriv->type);
         vcpupriv->type = g_steal_pointer(&info[i].type);
-        VIR_FREE(vcpupriv->alias);
-        vcpupriv->alias = g_steal_pointer(&info[i].alias);
+        if (info[i].alias) {
+            VIR_FREE(vcpupriv->alias);
+            vcpupriv->alias = g_steal_pointer(&info[i].alias);
+        }
         virJSONValueFree(vcpupriv->props);
         vcpupriv->props = g_steal_pointer(&info[i].props);
         vcpupriv->enable_id = info[i].id;

diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
index da92ced2f4443dde3e7a7aba3479540a30d79e06..6e300f547cf3ac2c899f42e292cb2925a4c268b5 100644 (file)
--- a/src/qemu/qemu_hotplug.c
+++ b/src/qemu/qemu_hotplug.c
@@ -6088,38 +6088,37 @@ qemuDomainRemoveVcpu(virDomainObj *vm,
     qemuDomainVcpuPrivate *vcpupriv = QEMU_DOMAIN_VCPU_PRIVATE(vcpuinfo);
     int oldvcpus = virDomainDefGetVcpus(vm->def);
     unsigned int nvcpus = vcpupriv->vcpus;
-    virErrorPtr save_error = NULL;
     size_t i;
+    ssize_t offlineVcpuWithTid = -1;
 
     if (qemuDomainRefreshVcpuInfo(vm, VIR_ASYNC_JOB_NONE, false) < 0)
         return -1;
 
-    /* validation requires us to set the expected state prior to calling it */
     for (i = vcpu; i < vcpu + nvcpus; i++) {
         vcpuinfo = virDomainDefGetVcpu(vm->def, i);
-        vcpuinfo->online = false;
+        vcpupriv = QEMU_DOMAIN_VCPU_PRIVATE(vcpuinfo);
+
+        if (vcpupriv->tid == 0) {
+            vcpuinfo->online = false;
+            /* Clear the alias as VCPU is now unplugged */
+            VIR_FREE(vcpupriv->alias);
+            ignore_value(virCgroupDelThread(priv->cgroup, VIR_CGROUP_THREAD_VCPU, i));
+        } else {
+            if (offlineVcpuWithTid == -1)
+                offlineVcpuWithTid = i;
+        }
     }
 
-    if (qemuDomainValidateVcpuInfo(vm) < 0) {
-        /* rollback vcpu count if the setting has failed */
+    if (offlineVcpuWithTid != -1) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("qemu reported thread id for inactive vcpu '%zu'"),
+                       offlineVcpuWithTid);
         virDomainAuditVcpu(vm, oldvcpus, oldvcpus - nvcpus, "update", false);
-
-        for (i = vcpu; i < vcpu + nvcpus; i++) {
-            vcpuinfo = virDomainDefGetVcpu(vm->def, i);
-            vcpuinfo->online = true;
-        }
         return -1;
     }
 
     virDomainAuditVcpu(vm, oldvcpus, oldvcpus - nvcpus, "update", true);
 
-    virErrorPreserveLast(&save_error);
-
-    for (i = vcpu; i < vcpu + nvcpus; i++)
-        ignore_value(virCgroupDelThread(priv->cgroup, VIR_CGROUP_THREAD_VCPU, i));
-
-    virErrorRestore(&save_error);
-
     return 0;
 }
 
@@ -6141,6 +6140,9 @@ qemuDomainRemoveVcpuAlias(virDomainObj *vm,
             return;
         }
     }
+
+    VIR_DEBUG("vcpu '%s' not found in vcpulist of domain '%s'",
+              alias, vm->def->name);
 }
 
 
@@ -6209,6 +6211,7 @@ qemuDomainHotplugAddVcpu(virQEMUDriver *driver,
     int rc;
     int oldvcpus = virDomainDefGetVcpus(vm->def);
     size_t i;
+    bool vcpuTidMissing = false;
 
     if (!qemuDomainSupportsNewVcpuHotplug(vm)) {
         virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
@@ -6238,20 +6241,26 @@ qemuDomainHotplugAddVcpu(virQEMUDriver *driver,
     if (qemuDomainRefreshVcpuInfo(vm, VIR_ASYNC_JOB_NONE, false) < 0)
         return -1;
 
-    /* validation requires us to set the expected state prior to calling it */
     for (i = vcpu; i < vcpu + nvcpus; i++) {
         vcpuinfo = virDomainDefGetVcpu(vm->def, i);
         vcpupriv = QEMU_DOMAIN_VCPU_PRIVATE(vcpuinfo);
 
         vcpuinfo->online = true;
 
-        if (vcpupriv->tid > 0 &&
-            qemuProcessSetupVcpu(vm, i, true) < 0)
-            return -1;
+        if (vcpupriv->tid > 0) {
+            if (qemuProcessSetupVcpu(vm, i, true) < 0) {
+                return -1;
+            }
+        } else {
+            vcpuTidMissing = true;
+        }
     }
 
-    if (qemuDomainValidateVcpuInfo(vm) < 0)
+    if (vcpuTidMissing && qemuDomainHasVcpuPids(vm)) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("qemu didn't report thread id for vcpu '%zu'"), i);
         return -1;
+    }
 
     qemuDomainVcpuPersistOrder(vm->def);