linux-kernel - Re: [PATCH v2 5/5] KVM: x86: improve reexecute

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Message-ID: <50CA9FA8.90109@linux.vnet.ibm.com>
Date:	Fri, 14 Dec 2012 11:40:24 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
To:	Marcelo Tosatti <mtosatti@...hat.com>
CC:	Gleb Natapov <gleb@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v2 5/5] KVM: x86: improve reexecute_instruction

On 12/14/2012 07:02 AM, Marcelo Tosatti wrote:

>>> Same comment as before: the only case where it should not attempt to 
>>> emulate is when there is a condition which makes it impossible to fix
>>> (the information is available to detect that condition).
>>>
>>> The earlier suggestion
>>>
>>> 	"How about recording the gfn number for shadow pages that have been
>>> shadowed in the current pagefault run?"
>>>
>>> Was about that.
>>
>> I think we can have a try. Is this change good to you, Marcelo?
>>
>> [eric@...alhost kvm]$ git diff
>> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
>> index 01d7c2a..e3d0001 100644
>> --- a/arch/x86/kvm/mmu.c
>> +++ b/arch/x86/kvm/mmu.c
>> @@ -4359,24 +4359,34 @@ unsigned int kvm_mmu_calculate_mmu_pages(struct kvm *kvm)
>>         return nr_mmu_pages;
>>  }
>>
>> -int kvm_mmu_get_spte_hierarchy(struct kvm_vcpu *vcpu, u64 addr, u64 sptes[4])
>> +void kvm_mmu_get_sp_hierarchy(struct kvm_vcpu *vcpu, u64 addr,
>> +                             struct kvm_mmu_sp_hierarchy *hierarchy)
>>  {
>>         struct kvm_shadow_walk_iterator iterator;
>>         u64 spte;
>> -       int nr_sptes = 0;
>> +
>> +       hierarchy->max_level = hierarchy->nr_levels = 0;
>>
>>         walk_shadow_page_lockless_begin(vcpu);
>>         for_each_shadow_entry_lockless(vcpu, addr, iterator, spte) {
>> -               sptes[iterator.level-1] = spte;
>> -               nr_sptes++;
>> +               struct kvm_mmu_page *sp =  page_header(__pa(iterator.sptep));
>> +
>> +               if (hierarchy->indirect_only && sp->role.direct)
>> +                       break;
>> +
>> +               if (!hierarchy->max_level)
>> +                       hierarchy->max_level = iterator.level;
>> +
>> +               hierarchy->shadow_gfns[iterator.level-1] = sp->gfn;
>> +               hierarchy->sptes[iterator.level-1] = spte;
>> +               hierarchy->nr_levels++;
>> +
>>                 if (!is_shadow_present_pte(spte))
>>                         break;
>>         }
>>         walk_shadow_page_lockless_end(vcpu);
>> -
>> -       return nr_sptes;
>>  }
> 
> Record gfns while shadowing in the vcpu struct, in a struct, along with cr2.
> Then validate 
> That way its guaranteed its not some other vcpu.

Okay, i will try this way. :)


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