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

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Date:	Thu, 24 Dec 2015 17:11:21 +0800
From:	Xiao Guangrong <guangrong.xiao@...ux.intel.com>
To:	Kai Huang <kai.huang@...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 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?


View attachment "0009-KVM-MMU-simplify-mmu_need_write_protect.patch" of type "text/x-patch" (2201 bytes)