Getting a complete list of features supported by a specific hypervisor on a given host requires taking the host-model CPU definition from virConnectGetDomainCapabilities
and passing it to virConnectBaselineHypervisorCPU with VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES flag.
But due to suboptimal initial design of CPU capabilities reporting, the CPU definition in virConnectGetDomainCapabilities uses <mode> top element while virConnectBaselineHypervisorCPU expects <cpu>. To avoid these extra steps the virConnectGetDomainCapabilities could support a new flag that would tell it to do the expansion itself.