linux-kernel - Re: [PATCH v2] KVM: MMU: optimize pte write path if don't have protected sp

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Date:	Wed, 11 May 2011 20:01:31 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Avi Kivity <avi@...hat.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v2] KVM: MMU: optimize pte write path if don't have protected
 sp

On 05/11/2011 07:28 PM, Avi Kivity wrote:
> On 05/11/2011 05:44 AM, Xiao Guangrong wrote:
>> Simply return from kvm_mmu_pte_write path if no shadow page is
>> write-protected, then we can avoid to walk all shadow pages and hold
>> mmu-lock
>>
>> @@ -1038,8 +1038,10 @@ static void kvm_mmu_free_page(struct kvm *kvm, struct kvm_mmu_page *sp)
>>       hlist_del(&sp->hash_link);
>>       list_del(&sp->link);
>>       free_page((unsigned long)sp->spt);
>> -    if (!sp->role.direct)
>> +    if (!sp->role.direct) {
>>           free_page((unsigned long)sp->gfns);
>> +        atomic_dec(&kvm->arch.indirect_shadow_pages);
>> +    }
>>       kmem_cache_free(mmu_page_header_cache, sp);
>>       kvm_mod_used_mmu_pages(kvm, -1);
>>   }
>> @@ -1536,6 +1538,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
>>               kvm_sync_pages(vcpu, gfn);
>>
>>           account_shadowed(vcpu->kvm, gfn);
>> +        atomic_inc(&vcpu->kvm->arch.indirect_shadow_pages);
>>       }
> 
> Better in account_shadowed()/unaccount_shadowed(), no?
> 

Yes, will fix. thanks for your reminder!

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