linux-kernel - Re: [PATCH v2 1/4] KVM: add spinlock optimization framework

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Date:   Tue, 8 Aug 2017 10:44:43 +0200
From:   David Hildenbrand <david@...hat.com>
To:     "Longpeng(Mike)" <longpeng2@...wei.com>, pbonzini@...hat.com,
        rkrcmar@...hat.com
Cc:     agraf@...e.com, borntraeger@...ibm.com, cohuck@...hat.com,
        christoffer.dall@...aro.org, marc.zyngier@....com,
        james.hogan@...tec.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, weidong.huang@...wei.com,
        arei.gonglei@...wei.com, wangxinxin.wang@...wei.com,
        longpeng.mike@...il.com
Subject: Re: [PATCH v2 1/4] KVM: add spinlock optimization framework

On 08.08.2017 10:42, David Hildenbrand wrote:
> 
>> +bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
>> +{
>> +	return false;
>> +}
> 
> why don't we need an EXPORT_SYMBOL here?
> 
>> +
>>  /* Just ensure a guest exit from a particular CPU */
>>  static void exit_vm_noop(void *info)
>>  {
>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>> index 15252d7..e7720d2 100644
>> --- a/virt/kvm/kvm_main.c
>> +++ b/virt/kvm/kvm_main.c
>> @@ -2317,7 +2317,7 @@ static bool kvm_vcpu_eligible_for_directed_yield(struct kvm_vcpu *vcpu)
>>  #endif
>>  }
>>  
>> -void kvm_vcpu_on_spin(struct kvm_vcpu *me)
>> +void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool me_in_kern)
>>  {
>>  	struct kvm *kvm = me->kvm;
>>  	struct kvm_vcpu *vcpu;
>> @@ -2348,6 +2348,8 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
>>  				continue;
>>  			if (swait_active(&vcpu->wq) && !kvm_arch_vcpu_runnable(vcpu))
>>  				continue;
>> +			if (me_in_kern && !kvm_arch_vcpu_in_kernel(vcpu))
>> +				continue;
> 
> 
> hm, does this patch compile? (me_in_kern)

pardon me, missed the parameter, so ignore this comment. comment
regarding splitting up below still holds :)

> 
> I would even move this to an other patch.
> 
> Maybe even split into
> 
> a) introducing kvm_arch_vcpu_in_kernel() for all archs
> b) modifying kvm_vcpu_on_spin(), passing the result from
> kvm_arch_vcpu_in_kernel()
> c) filling kvm_arch_vcpu_in_kernel() with life for different archs
> (multiple patches)
> d) pimping kvm_vcpu_on_spin()
> 
>>  			if (!kvm_vcpu_eligible_for_directed_yield(vcpu))
>>  				continue;
>>  
>>
> 
> 


-- 

Thanks,

David