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The RPC code assumed that the array returned by the driver would be fully populated; that is, ncpus on entry resulted in ncpus * return value on exit. However, while we don't support holes in the middle of ncpus, we do want to permit the case of ncpus on entry being longer than the array returned by the driver (that is, it should be safe for the caller to pass ncpus=128 on entry, and the driver will stop populating the array when it hits max_id). Additionally, a successful return implies that the caller will then use virTypedParamArrayClear on the entire array; for this to not free uninitialized memory, the driver must ensure that all skipped entries are explicitly zeroed (the RPC driver did this, but not the qemu driver). There are now three cases: server 0.9.10 and client 0.9.10 or newer: No impact - there were no hypervisor drivers that supported cpu stats server 0.9.11 or newer and client 0.9.10: if the client calls with ncpus beyond the max, then the rpc call will fail on the client side and disconnect the client, but the server is no worse for the wear server 0.9.11 or newer and client 0.9.11: the server can return a truncated array and the client will do just fine I reproduced the problem by using a host with 2 CPUs, and doing: virsh cpu-stats $dom --start 1 --count 2 * daemon/remote.c (remoteDispatchDomainGetCPUStats): Allow driver to omit tail of array. * src/remote/remote_driver.c (remoteDomainGetCPUStats): Accommodate driver that omits tail of array. * src/libvirt.c (virDomainGetCPUStats): Document this. * src/qemu/qemu_driver.c (qemuDomainGetPercpuStats): Clear all unpopulated entries. |
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| qemu_protocol.x | ||
| remote_driver.c | ||
| remote_driver.h | ||
| remote_protocol.x | ||