Roman Kagan <rkagan@xxxxxxxxxxxxx> writes: > On Fri, Jun 29, 2018 at 05:21:47PM +0200, Vitaly Kuznetsov wrote: >> Roman Kagan <rkagan@xxxxxxxxxxxxx> writes: >> >> > On Fri, Jun 29, 2018 at 04:14:53PM +0200, Vitaly Kuznetsov wrote: >> >> VP_INDEX almost always matches VCPU id and get_vcpu_by_vpidx() is fast, >> >> use it instead of traversing full vCPU list every time. >> >> >> >> To support the change switch kvm_make_vcpus_request_mask() to checking >> >> vcpu_id instead of vcpu index, >> > >> > I'm afraid you can't do this: vcpu_id (== apic id) can be sparse, i.e. >> > it's not very well suited for bitmaps and can exceed the max number of >> > vcpus. >> >> True. The bitmap should be of KVM_MAX_VCPU_ID size, not >> KVM_MAX_VCPUS. >> >> Unfortunately there's no convenient way to get VCPU idx from VCPU >> id, kvm_vcpu_get_idx() just walks the whole list :-( I see two possible >> options: >> 1) Add vcpu_idx fields to struct kvm_vcpu >> 2) Keep the change expecting masks of KVM_MAX_VCPU_ID in >> kvm_make_vcpus_request_mask(). KVM_MAX_VCPU_ID is currently 1023 so our >> bitmaps will be 16 longs long. Not sure if it's too much. > > 3) rework get_vcpu_by_vpidx into get_vcpu_idx_by_vpidx followed by > get_cpu, and use the former for your purposes > 4) duplicate get_vcpu_by_vpidx logic in get_vcpu_idx_by_vpidx Oh, true, thanks! > > Roman. > > P.S. I'm starting to wonder how safe this get_vcpu_* thing is WRT vcpu > removal, but that's a different story anyway. As there's no CPU removal in real Hyper-V I'd expect us to find a number of issues with Windows guests if we go down this road :-) -- Vitaly
