linux-kernel - Re: [PATCH v2 09/11] KVM: MMU: simplify mmu_need_write

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Date:	Thu, 24 Dec 2015 17:21:58 +0800
From:	Kai Huang <kai.huang@...ux.intel.com>
To:	Xiao Guangrong <guangrong.xiao@...ux.intel.com>,
	pbonzini@...hat.com
Cc:	gleb@...nel.org, mtosatti@...hat.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, jike.song@...el.com
Subject: Re: [PATCH v2 09/11] KVM: MMU: simplify mmu_need_write_protect



On 12/24/2015 05:11 PM, Xiao Guangrong wrote:
>
>
> On 12/24/2015 04:36 PM, Kai Huang wrote:
>>
>>
>> On 12/23/2015 07:25 PM, Xiao Guangrong wrote:
>>> Now, all non-leaf shadow page are page tracked, if gfn is not tracked
>>> there is no non-leaf shadow page of gfn is existed, we can directly
>>> make the shadow page of gfn to unsync
>>>
>>> Signed-off-by: Xiao Guangrong <guangrong.xiao@...ux.intel.com>
>>> ---
>>>   arch/x86/kvm/mmu.c | 26 ++++++++------------------
>>>   1 file changed, 8 insertions(+), 18 deletions(-)
>>>
>>> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
>>> index 5a2ca73..f89e77f 100644
>>> --- a/arch/x86/kvm/mmu.c
>>> +++ b/arch/x86/kvm/mmu.c
>>> @@ -2461,41 +2461,31 @@ static void __kvm_unsync_page(struct 
>>> kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
>>>       kvm_mmu_mark_parents_unsync(sp);
>>>   }
>>> -static void kvm_unsync_pages(struct kvm_vcpu *vcpu,  gfn_t gfn)
>>> +static bool kvm_unsync_pages(struct kvm_vcpu *vcpu, gfn_t gfn,
>>> +                 bool can_unsync)
>>>   {
>>>       struct kvm_mmu_page *s;
>>>       for_each_gfn_indirect_valid_sp(vcpu->kvm, s, gfn) {
>>> +        if (!can_unsync)
>>> +            return true;
>>> +
>>>           if (s->unsync)
>>>               continue;
>>>           WARN_ON(s->role.level != PT_PAGE_TABLE_LEVEL);
>>>           __kvm_unsync_page(vcpu, s);
>>>       }
>>> +
>>> +    return false;
>>>   }
>> I hate to say but it looks odd to me that kvm_unsync_pages takes a 
>> bool parameter called can_unsync,
>> and return a bool (which looks like suggesting whether the unsync has 
>> succeeded or not). How about
>> calling __kvm_unsync_pages directly in mmu_need_write_protect, and 
>> leave kvm_unsync_pages unchanged
>> (or even remove it as looks it is used nowhere else) ? But again it's 
>> to you and Paolo.
>>
>
> Make senses, the updated version is attached, count you review it?
Sure and it looks good to me.

Thanks,
-Kai
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