For our administration, we need the following actions, while concerned domain is running: 1) Change the number of virtual CPUs. 2) Change the pinning (affinity) of a virtual CPU on real CPUs. 3) Get detailed information for each virtual CPU. Currently there is no Libvirt function provided for that. We suggest to add the following 3 functions (in libvirt.c): <tt>/**</tt> <tt> * virDomainSetVcpus:</tt> <tt> * @domain: pointer to domain object, or NULL for Domain0</tt> <tt> * @nvcpus: the new number of virtual CPUs for this domain</tt> <tt> *</tt> <tt> * Dynamically change the number of virtual CPUs used by the domain.</tt> <tt> * Note that this call may fail if the underlying virtualization hypervisor</tt> <tt> * does not support it or if growing the number is arbitrary limited.</tt> <tt> * This function requires priviledged access to the hypervisor.</tt> <tt> *</tt> <tt> * Returns 0 in case of success, -1 in case of failure.</tt> <tt> */</tt> <tt>int virDomainSetVcpus(virDomainPtr domain, unsigned int nvcpus)</tt> <tt>/**</tt> <tt> * virDomainPinVcpu:</tt> <tt> * @domain: pointer to domain object, or NULL for Domain0</tt> <tt> * @vcpu: virtual CPU number</tt> <tt> * @cpumap: pointer to a bit map of real CPUs (format in virVcpuInfo)</tt> <tt> * @maplen: length of cpumap, in 8-bit bytes</tt> <tt> * </tt> <tt> * Dynamically change the real CPUs which can be allocated to a virtual CPU.</tt> <tt> * This function requires priviledged access to the hypervisor.</tt> <tt> *</tt> <tt> * Returns 0 in case of success, -1 in case of failure.</tt> <tt> */</tt> <tt>int virDomainPinVcpu(virDomainPtr domain, unsigned int vcpu,</tt> <tt> unsigned char *cpumap, int maplen)</tt> <tt>/**</tt> <tt> * virDomainGetVcpus:</tt> <tt> * @domain: pointer to domain object, or NULL for Domain0</tt> <tt> * @info: pointer to an array of virVcpuInfo structures</tt> <tt> * @maxinfo: number of structures in info array</tt> <tt> * </tt> <tt> * Extract information about virtual CPUs of a domain, store it in info array.</tt> <tt> *</tt> <tt> * Returns the number of info filled in case of success, -1 in case of failure.</tt> <tt> */</tt> <tt>int virDomainGetVcpus(virDomainPtr domain, virVcpuInfoPtr info, int maxinfo)</tt> with the following structure (in libvirt.h): <tt>/**</tt> <tt> * virVcpuInfo: structure for information about a virtual CPU in a domain.</tt> <tt> */</tt> <tt>#define VIR_MAX_CPUS 256</tt> <tt>typedef enum {</tt> <tt> VIR_VCPU_OFFLINE = 0, /* the virtual CPU is offline */</tt> <tt> VIR_VCPU_RUNNING = 1, /* the virtual CPU is running */</tt> <tt> VIR_VCPU_BLOCKED = 2, /* the virtual CPU is blocked on resource */</tt> <tt>} virVcpuState;</tt> <tt>typedef struct _virVcpuInfo virVcpuInfo;</tt> <tt>struct _virVcpuInfo {</tt> <tt> unsigned int number; /* virtual CPU number */</tt> <tt> int state; /* value from virVcpuState */</tt> <tt> unsigned long long cpuTime; /* CPU time used, in nanoseconds */</tt> <tt> int cpu; /* real CPU number, or -1 if offline */</tt> <tt> unsigned char cpumap[VIR_MAX_CPUS/8]; /* Bit map of usable real CPUs.</tt> <tt> Each bit set to 1 means that corresponding CPU is usable.</tt> <tt> Bytes are stored in little-endian order: CPU0-7, 8-15...</tt> <tt> In each byte, lowest CPU number is least significant bit */</tt> <tt>};</tt> <tt>typedef virVcpuInfo *virVcpuInfoPtr;</tt> I have successfully tried those functions via Xen hypervisor, except for the first (SetVcpus) where hypervisor operation DOM0_MAX_VCPUS fails (maybe it is not possible on a running domain ?). That function was successful via Xen daemon.