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[PATCH v2 09/11] KVM: MMU: simplify mmu_need_write_protect

Started byXiao Guangrong <guangrong.xiao@linux.intel.com>
First post2015-12-23 12:40 +0100
Last post2015-12-24 10:30 +0100
Articles 4 — 2 participants

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  [PATCH v2 09/11] KVM: MMU: simplify mmu_need_write_protect Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2015-12-23 12:40 +0100
    Re: [PATCH v2 09/11] KVM: MMU: simplify mmu_need_write_protect Kai Huang <kai.huang@linux.intel.com> - 2015-12-24 09:50 +0100
      Re: [PATCH v2 09/11] KVM: MMU: simplify mmu_need_write_protect Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2015-12-24 10:20 +0100
        Re: [PATCH v2 09/11] KVM: MMU: simplify mmu_need_write_protect Kai Huang <kai.huang@linux.intel.com> - 2015-12-24 10:30 +0100

#1297387 — [PATCH v2 09/11] KVM: MMU: simplify mmu_need_write_protect

FromXiao Guangrong <guangrong.xiao@linux.intel.com>
Date2015-12-23 12:40 +0100
Subject[PATCH v2 09/11] KVM: MMU: simplify mmu_need_write_protect
Message-ID<qIPVU-yO-23@gated-at.bofh.it>
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@linux.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;
 }
 
 static bool mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn,
 				   bool can_unsync)
 {
-	struct kvm_mmu_page *s;
-	bool need_unsync = false;
-
 	if (kvm_page_track_check_mode(vcpu, gfn, KVM_PAGE_TRACK_WRITE))
 		return true;
 
-	for_each_gfn_indirect_valid_sp(vcpu->kvm, s, gfn) {
-		if (!can_unsync)
-			return true;
-
-		if (s->role.level != PT_PAGE_TABLE_LEVEL)
-			return true;
-
-		if (!s->unsync)
-			need_unsync = true;
-	}
-	if (need_unsync)
-		kvm_unsync_pages(vcpu, gfn);
-
-	return false;
+	return kvm_unsync_pages(vcpu, gfn, can_unsync);
 }
 
 static bool kvm_is_mmio_pfn(pfn_t pfn)
-- 
1.8.3.1

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#1297783

FromKai Huang <kai.huang@linux.intel.com>
Date2015-12-24 09:50 +0100
Message-ID<qJ9KV-4un-1@gated-at.bofh.it>
In reply to#1297387

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@linux.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.

Thanks,
-Kai
>   
>   static bool mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn,
>   				   bool can_unsync)
>   {
> -	struct kvm_mmu_page *s;
> -	bool need_unsync = false;
> -
>   	if (kvm_page_track_check_mode(vcpu, gfn, KVM_PAGE_TRACK_WRITE))
>   		return true;
>   
> -	for_each_gfn_indirect_valid_sp(vcpu->kvm, s, gfn) {
> -		if (!can_unsync)
> -			return true;
> -
> -		if (s->role.level != PT_PAGE_TABLE_LEVEL)
> -			return true;
> -
> -		if (!s->unsync)
> -			need_unsync = true;
> -	}
> -	if (need_unsync)
> -		kvm_unsync_pages(vcpu, gfn);
> -
> -	return false;
> +	return kvm_unsync_pages(vcpu, gfn, can_unsync);
>   }
>   
>   static bool kvm_is_mmio_pfn(pfn_t pfn)

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#1297788

FromXiao Guangrong <guangrong.xiao@linux.intel.com>
Date2015-12-24 10:20 +0100
Message-ID<qJadY-4TB-3@gated-at.bofh.it>
In reply to#1297783

[Multipart message — attachments visible in raw view] — view raw

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@linux.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?

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#1297795

FromKai Huang <kai.huang@linux.intel.com>
Date2015-12-24 10:30 +0100
Message-ID<qJanD-4WC-11@gated-at.bofh.it>
In reply to#1297788

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@linux.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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