vcpu: implement the public APIs

Factors common checks (such as nonzero vcpu count) up front, but
drivers will still need to do additional flag checks.

* src/libvirt.c (virDomainSetVcpusFlags, virDomainGetVcpusFlags):
New functions.
(virDomainSetVcpus, virDomainGetMaxVcpus): Refer to new API.

src/libvirt.c

@@ -5192,7 +5192,9 @@ error:
  * This function requires privileged access to the hypervisor.
  *
  * This command only changes the runtime configuration of the domain,
- * so can only be called on an active domain.
+ * so can only be called on an active domain.  It is hypervisor-dependent
+ * whether it also affects persistent configuration; for more control,
+ * use virDomainSetVcpusFlags().
  *
  * Returns 0 in case of success, -1 in case of failure.
  */
@@ -5236,6 +5238,132 @@ error:
     return -1;
 }
 
+/**
+ * virDomainSetVcpusFlags:
+ * @domain: pointer to domain object, or NULL for Domain0
+ * @nvcpus: the new number of virtual CPUs for this domain, must be at least 1
+ * @flags: an OR'ed set of virDomainVcpuFlags
+ *
+ * Dynamically change the number of virtual CPUs used by the domain.
+ * Note that this call may fail if the underlying virtualization hypervisor
+ * does not support it or if growing the number is arbitrary limited.
+ * This function requires privileged access to the hypervisor.
+ *
+ * @flags must include VIR_DOMAIN_VCPU_LIVE to affect a running
+ * domain (which may fail if domain is not active), or
+ * VIR_DOMAIN_VCPU_CONFIG to affect the next boot via the XML
+ * description of the domain.  Both flags may be set.
+ *
+ * If @flags includes VIR_DOMAIN_VCPU_MAXIMUM, then
+ * VIR_DOMAIN_VCPU_LIVE must be clear, and only the maximum virtual
+ * CPU limit is altered; generally, this value must be less than or
+ * equal to virConnectGetMaxVcpus().  Otherwise, this call affects the
+ * current virtual CPU limit, which must be less than or equal to the
+ * maximum limit.
+ *
+ * Returns 0 in case of success, -1 in case of failure.
+ */
+
+int
+virDomainSetVcpusFlags(virDomainPtr domain, unsigned int nvcpus,
+                       unsigned int flags)
+{
+    virConnectPtr conn;
+    DEBUG("domain=%p, nvcpus=%u, flags=%u", domain, nvcpus, flags);
+
+    virResetLastError();
+
+    if (!VIR_IS_CONNECTED_DOMAIN(domain)) {
+        virLibDomainError(NULL, VIR_ERR_INVALID_DOMAIN, __FUNCTION__);
+        virDispatchError(NULL);
+        return (-1);
+    }
+    if (domain->conn->flags & VIR_CONNECT_RO) {
+        virLibDomainError(domain, VIR_ERR_OPERATION_DENIED, __FUNCTION__);
+        goto error;
+    }
+
+    /* Perform some argument validation common to all implementations.  */
+    if (nvcpus < 1 || (unsigned short) nvcpus != nvcpus ||
+        (flags & (VIR_DOMAIN_VCPU_LIVE | VIR_DOMAIN_VCPU_CONFIG)) == 0) {
+        virLibDomainError(domain, VIR_ERR_INVALID_ARG, __FUNCTION__);
+        goto error;
+    }
+    conn = domain->conn;
+
+    if (conn->driver->domainSetVcpusFlags) {
+        int ret;
+        ret = conn->driver->domainSetVcpusFlags (domain, nvcpus, flags);
+        if (ret < 0)
+            goto error;
+        return ret;
+    }
+
+    virLibConnError (conn, VIR_ERR_NO_SUPPORT, __FUNCTION__);
+
+error:
+    virDispatchError(domain->conn);
+    return -1;
+}
+
+/**
+ * virDomainGetVcpusFlags:
+ * @domain: pointer to domain object, or NULL for Domain0
+ * @flags: an OR'ed set of virDomainVcpuFlags
+ *
+ * Query the number of virtual CPUs used by the domain.  Note that
+ * this call may fail if the underlying virtualization hypervisor does
+ * not support it.  This function requires privileged access to the
+ * hypervisor.
+ *
+ * @flags must include either VIR_DOMAIN_VCPU_ACTIVE to query a
+ * running domain (which will fail if domain is not active), or
+ * VIR_DOMAIN_VCPU_PERSISTENT to query the XML description of the
+ * domain.  It is an error to set both flags.
+ *
+ * If @flags includes VIR_DOMAIN_VCPU_MAXIMUM, then the maximum
+ * virtual CPU limit is queried.  Otherwise, this call queries the
+ * current virtual CPU limit.
+ *
+ * Returns 0 in case of success, -1 in case of failure.
+ */
+
+int
+virDomainGetVcpusFlags(virDomainPtr domain, unsigned int flags)
+{
+    virConnectPtr conn;
+    DEBUG("domain=%p, flags=%u", domain, flags);
+
+    virResetLastError();
+
+    if (!VIR_IS_CONNECTED_DOMAIN(domain)) {
+        virLibDomainError(NULL, VIR_ERR_INVALID_DOMAIN, __FUNCTION__);
+        virDispatchError(NULL);
+        return (-1);
+    }
+
+    /* Exactly one of these two flags should be set.  */
+    if (!(flags & VIR_DOMAIN_VCPU_LIVE) == !(flags & VIR_DOMAIN_VCPU_CONFIG)) {
+        virLibDomainError(domain, VIR_ERR_INVALID_ARG, __FUNCTION__);
+        goto error;
+    }
+    conn = domain->conn;
+
+    if (conn->driver->domainGetVcpusFlags) {
+        int ret;
+        ret = conn->driver->domainGetVcpusFlags (domain, flags);
+        if (ret < 0)
+            goto error;
+        return ret;
+    }
+
+    virLibConnError (conn, VIR_ERR_NO_SUPPORT, __FUNCTION__);
+
+error:
+    virDispatchError(domain->conn);
+    return -1;
+}
+
 /**
  * virDomainPinVcpu:
  * @domain: pointer to domain object, or NULL for Domain0
@@ -5371,9 +5499,9 @@ error:
  *
  * Provides the maximum number of virtual CPUs supported for
  * the guest VM. If the guest is inactive, this is basically
- * the same as virConnectGetMaxVcpus. If the guest is running
+ * the same as virConnectGetMaxVcpus(). If the guest is running
  * this will reflect the maximum number of virtual CPUs the
- * guest was booted with.
+ * guest was booted with.  For more details, see virDomainGetVcpusFlags().
  *
  * Returns the maximum of virtual CPU or -1 in case of error.
  */