Wanpeng Li <kernellwp@xxxxxxxxx> writes: >> >> Honestly, I'd simplify the check in kvm_alloc_cpumask() as >> >> if (!kvm_para_available()) >> return; >> >> and allocated masks for all other cases. > > This will waste the memory if pv tlb and pv ipis are not exposed which > are the only users currently. > My assumption is that the number of cases where we a) expose KVM b) don't expose IPIs and PV-TLB and c) care about 1 cpumask per cpu is relatively low. Ok, let's at least have a function for if (kvm_para_has_feature(KVM_FEATURE_PV_TLB_FLUSH) && !kvm_para_has_hint(KVM_HINTS_REALTIME) && kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) as we now check it twice: in kvm_alloc_cpumask() and kvm_guest_init(), something like pv_tlb_flush_supported(). We can also do pv_ipi_supported() and probably others for consistency. Also, probably not for this patch but it all makes me wonder why there's no per-cpu 'scratch' cpumask for the whole kernel to use. We definitely need it for hypervisor support but I also see arch/x86/kernel/apic/x2apic_cluster.c has similar needs. -- Vitaly
