Paolo Bonzini <pbonzini@xxxxxxxxxx> writes: > On 11/12/21 15:02, Marc Zyngier wrote: >>> I'd like KVM to be consistent across architectures and have the same >>> (similar) meaning for KVM_CAP_NR_VCPUS. >> Sure, but this is a pretty useless piece of information anyway. As >> Andrew pointed out, the information is available somewhere else, and >> all we need to do is to cap it to the number of supported vcpus, which >> is effectively a KVM limitation. >> >> Also, we are talking about representing the architecture to userspace. >> No amount of massaging is going to make an arm64 box look like an x86. > > Not sure what you mean? The API is about providing a piece of > information independent of the architecture, while catering for a ppc > weirdness. Yes it's mostly useless if you don't care about ppc, but > it's not about making arm64 look like x86 or ppc; it's about not having > to special case ppc in userspace. > > If anything, if KVM_CAP_NR_VCPUS returns the same for kvm and !kvm, then > *that* is making an arm64 box look like an x86. On ARM the max vCPUs > depends on VM's GIC configuration, so KVM_CAP_NR_VCPUS should take that > into account. (I'm about to send v2 as we have s390 sorted out.) So what do we decide about ARM? - Current approach (kvm->arch.max_vcpus/kvm_arm_default_max_vcpus() depending on 'if (kvm)') - that would be my preference. - Always kvm_arm_default_max_vcpus to make the output independent on 'if (kvm)'. - keep the status quo (drop the patch). Please advise) -- Vitaly
