On 10/3/19 10:02 AM, Zhenzhong Duan wrote:
> void __init kvm_spinlock_init(void)
> {
> - /* Does host kernel support KVM_FEATURE_PV_UNHALT? */
> - if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
> - return;
> -
> - if (kvm_para_has_hint(KVM_HINTS_REALTIME))
> + /*
> + * Don't use the pvqspinlock code if no KVM_FEATURE_PV_UNHALT feature
> + * support, or there is REALTIME hints or only 1 vCPU.
> + */
> + if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT) ||
> + kvm_para_has_hint(KVM_HINTS_REALTIME) ||
> + num_possible_cpus() == 1) {
> + pr_info("PV spinlocks disabled\n");
> return;
> + }
>
> - /* Don't use the pvqspinlock code if there is only 1 vCPU. */
> - if (num_possible_cpus() == 1)
> + if (nopvspin) {
> + pr_info("PV spinlocks disabled forced by \"nopvspin\" parameter.\n");
> + static_branch_disable(&virt_spin_lock_key);
Would it make sense to bring here the other site where the key is
disabled (in kvm_smp_prepare_cpus())?
(and, in fact, shouldn't all of the checks that result in early return
above disable the key?)
-boris
> return;
> + }
> + pr_info("PV spinlocks enabled\n");
>
> __pv_init_lock_hash();
> pv_ops.lock.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
>
