What does it mean to be "pinned" to all available physical CPUs?
Isso significa que ele estará livre para rodar em qualquer uma das CPUs fisicamente disponíveis no sistema host.
O parágrafo original da documentação do KVM ...The optional attribute placement can be used to indicate the CPU placement mode for domain process, its value can be either static or auto, which defaults to placement, or numatune, or static if cpuset is specified. auto indicates the domain process will be pinned to the advisory nodeset from querying numad, and the value of attribute cpuset will be ignored if it's specified. If both cpuset and placement are not specified, or if placement is static, but no cpuset is specified, the domain process will be pinned to all the available physical CPUs.
Fonte: 20.4. Alocação de CPU