On 2019/10/7 22:46, Boris Ostrovsky wrote:
On 10/6/19 3:49 AM, Zhenzhong Duan wrote:
On 2019/10/4 22:52, Boris Ostrovsky wrote:
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())?
Thanks for point out, I'll do it. Just not clear if I should do that
in a separate patch,
there is a history about that code:
Its original place was here and then moved to kvm_smp_prepare_cpus()
by below commit:
34226b6b ("KVM: X86: Fix setup the virt_spin_lock_key before static
key get initialized")
which fixed jump_label_init() calling late issue.
Then 8990cac6 ("x86/jump_label: Initialize static branching early")
move jump_label_init()
early, so commit 34226b6b could be reverted.
Which is similar to what you did earlier for Xen.
You remember that, ok, I'll do the same for KVM.
Thanks
Zhenzhong
