Re: [PATCH v2 3/3] KVM: x86: use static calls to reduce kvm_x86_ops overhead

Paolo Bonzini
2021-01-15T13:58:30Z

On 15/01/21 10:45, Peter Zijlstra wrote:
> On Thu, Jan 14, 2021 at 10:27:56PM -0500, Jason Baron wrote:
>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>> index 5060922..9d4492b 100644
>> --- a/arch/x86/include/asm/kvm_host.h
>> +++ b/arch/x86/include/asm/kvm_host.h
>> @@ -1350,7 +1350,7 @@ void kvm_arch_free_vm(struct kvm *kvm);
>> static inline int kvm_arch_flush_remote_tlb(struct kvm *kvm)
>> {
>> if (kvm_x86_ops.tlb_remote_flush &&
>> - !kvm_x86_ops.tlb_remote_flush(kvm))
>> + !static_call(kvm_x86_tlb_remote_flush)(kvm))
>> return 0;
>> else
>> return -ENOTSUPP;
>
> Would you be able to use something like this?
>
> https://lkml.kernel.org/r/20201110101307.GO2651@hirez.programming.kicks-ass.net
>
> we could also add __static_call_return1(), if that would help.
>

I think I'd rather make the default callee return -ENOTSUPP directly and
remove the "if" completely. So __static_call_return1() is not
particularly useful here.

Paolo