Sean Christopherson <seanjc@xxxxxxxxxx> writes:
> On Fri, Aug 27, 2021, Vitaly Kuznetsov wrote:
>> Allocating cpumask dynamically in zalloc_cpumask_var() is not ideal.
>> Allocation is somewhat slow and can (in theory and when CPUMASK_OFFSTACK)
>> fail. kvm_make_all_cpus_request_except() already disables preemption so
>> we can use pre-allocated per-cpu cpumasks instead.
>>
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
>> ---
>> virt/kvm/kvm_main.c | 29 +++++++++++++++++++++++------
>> 1 file changed, 23 insertions(+), 6 deletions(-)
>>
>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>> index 2e9927c4eb32..2f5fe4f54a51 100644
>> --- a/virt/kvm/kvm_main.c
>> +++ b/virt/kvm/kvm_main.c
>> @@ -155,6 +155,8 @@ static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm);
>> static unsigned long long kvm_createvm_count;
>> static unsigned long long kvm_active_vms;
>>
>> +static DEFINE_PER_CPU(cpumask_var_t, cpu_kick_mask);
>> +
>> __weak void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm,
>> unsigned long start, unsigned long end)
>> {
>> @@ -323,14 +325,15 @@ bool kvm_make_all_cpus_request_except(struct kvm *kvm, unsigned int req,
>> struct kvm_vcpu *except)
>> {
>> struct kvm_vcpu *vcpu;
>> - cpumask_var_t cpus;
>> + struct cpumask *cpus;
>> bool called;
>> int i, me;
>>
>> - zalloc_cpumask_var(&cpus, GFP_ATOMIC);
>> -
>> me = get_cpu();
>>
>> + cpus = this_cpu_cpumask_var_ptr(cpu_kick_mask);
>> + cpumask_clear(cpus);
>> +
>> kvm_for_each_vcpu(i, vcpu, kvm) {
>> if (vcpu == except)
>> continue;
>> @@ -340,7 +343,6 @@ bool kvm_make_all_cpus_request_except(struct kvm *kvm, unsigned int req,
>> called = kvm_kick_many_cpus(cpus, !!(req & KVM_REQUEST_WAIT));
>> put_cpu();
>>
>> - free_cpumask_var(cpus);
>> return called;
>> }
>>
>> @@ -5581,9 +5583,15 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
>> goto out_free_3;
>> }
>>
>> + for_each_possible_cpu(cpu) {
>> + if (!alloc_cpumask_var_node(&per_cpu(cpu_kick_mask, cpu),
>> + GFP_KERNEL, cpu_to_node(cpu)))
>> + goto out_free_4;
>
> 'r' needs to be explicitly set to -EFAULT, e.g. in the current code it's
> guaranteed to be 0 here.
Oops, yes. Any particular reason to avoid -ENOMEM? (hope not, will use
this in v5)
>
>> + }
>> +
>> r = kvm_async_pf_init();
>> if (r)
>> - goto out_free;
>> + goto out_free_5;
>>
>> kvm_chardev_ops.owner = module;
>> kvm_vm_fops.owner = module;
>> @@ -5609,7 +5617,11 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
>>
>> out_unreg:
>> kvm_async_pf_deinit();
>> -out_free:
>> +out_free_5:
>> + for_each_possible_cpu(cpu) {
>
> Unnecessary braces.
>
>> + free_cpumask_var(per_cpu(cpu_kick_mask, cpu));
>> + }
>> +out_free_4:
>> kmem_cache_destroy(kvm_vcpu_cache);
>> out_free_3:
>> unregister_reboot_notifier(&kvm_reboot_notifier);
>> @@ -5629,8 +5641,13 @@ EXPORT_SYMBOL_GPL(kvm_init);
>>
>> void kvm_exit(void)
>> {
>> + int cpu;
>> +
>> debugfs_remove_recursive(kvm_debugfs_dir);
>> misc_deregister(&kvm_dev);
>> + for_each_possible_cpu(cpu) {
>
> Same here.
>
>> + free_cpumask_var(per_cpu(cpu_kick_mask, cpu));
>> + }
>> kmem_cache_destroy(kvm_vcpu_cache);
>> kvm_async_pf_deinit();
>> unregister_syscore_ops(&kvm_syscore_ops);
>> --
>> 2.31.1
>>
>
--
Vitaly
