Sean Christopherson <seanjc@xxxxxxxxxx> writes:
> On Thu, Aug 26, 2021, Vitaly Kuznetsov wrote:
>> Iterating over set bits in 'vcpu_bitmap' should be faster than going
>> through all vCPUs, especially when just a few bits are set.
>>
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
>> ---
>
> ...
>
>> + if (vcpu_bitmap) {
>> + for_each_set_bit(i, vcpu_bitmap, KVM_MAX_VCPUS) {
>> + vcpu = kvm_get_vcpu(kvm, i);
>> + if (!vcpu || vcpu == except)
>> + continue;
>> + kvm_make_vcpu_request(kvm, vcpu, req, tmp, me);
>> + }
>> + } else {
>> + kvm_for_each_vcpu(i, vcpu, kvm) {
>> + if (vcpu == except)
>> + continue;
>> + kvm_make_vcpu_request(kvm, vcpu, req, tmp, me);
>> }
>> }
>
> Rather than feed kvm_make_all_cpus_request_except() into kvm_make_vcpus_request_mask(),
> I think it would be better to move the kvm_for_each_vcpu() path into
> kvm_make_all_cpus_request_except() (see bottom of the mail). That eliminates the
> silliness of calling a "mask" function without a mask, and also allows a follow-up
> patch to drop @except from kvm_make_vcpus_request_mask(), which is truly nonsensical
> as the caller can and should simply not set that vCPU in the mask.
Both make perfect sense, thanks! v4 is being prepared.
--
Vitaly
