Re: [PATCH v7 2/4] KVM: X86: Add Paravirt TLB Shootdown

Wanpeng Li
2017-12-01T00:56:02Z

2017-11-30 23:17 GMT+08:00 Radim Krčmář <rkrcmar@redhat.com>:
> 2017-11-29 22:01-0800, Wanpeng Li:
>> From: Wanpeng Li <wanpeng.li@hotmail.com>
>> ---
>> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
>> @@ -498,6 +498,34 @@ static void __init kvm_apf_trap_init(void)
>> update_intr_gate(X86_TRAP_PF, async_page_fault);
>> }
>>
>> +static DEFINE_PER_CPU(cpumask_var_t, __pv_tlb_mask);
>> +
>> +static void kvm_flush_tlb_others(const struct cpumask *cpumask,
>> + const struct flush_tlb_info *info)
>> +{
>> + u8 state;
>> + int cpu;
>> + struct kvm_steal_time *src;
>> + struct cpumask *flushmask = this_cpu_cpumask_var_ptr(__pv_tlb_mask);
>> +
>> + cpumask_copy(flushmask, cpumask);
>
> Is it impossible to call this function before the allocation?
>
> I was guessing that early_initcall might allow us to avoid a (static)
> condition as there is no point in calling when there are no others, but
> expected the worst ...

kernel_init()
-> kernel_init_freeable()
-> do_basic_setup()
-> do_initcalls()
-> async_synchronize_full() => finish all async __init code
-> try_to_run_init_process()

All the async __init codes can guarantee to be completed before init
task is created, so I think arch_initcall() is fine.

Regards,
Wanpeng Li