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

[Xiao Guangrong <guangrong.xiao@linux.intel.com>]

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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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>From a634f139dd9c8d0068f17b5c93cadcf979ac8acc Mon Sep 17 00:00:00 2001
From: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Date: Thu, 24 Dec 2015 17:03:04 +0800
Subject: [PATCH 09/11] KVM: MMU: simplify mmu_need_write_protect

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 | 29 +++++++----------------------
 1 file changed, 7 insertions(+), 22 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 5a2ca73..d6be758 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2452,7 +2452,7 @@ int kvm_mmu_unprotect_page(struct kvm *kvm, gfn_t gfn)
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_unprotect_page);
 
-static void __kvm_unsync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
+static void kvm_unsync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
 {
 	trace_kvm_mmu_unsync_page(sp);
 	++vcpu->kvm->stat.mmu_unsync;
@@ -2461,39 +2461,24 @@ 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)
-{
-	struct kvm_mmu_page *s;
-
-	for_each_gfn_indirect_valid_sp(vcpu->kvm, s, gfn) {
-		if (s->unsync)
-			continue;
-		WARN_ON(s->role.level != PT_PAGE_TABLE_LEVEL);
-		__kvm_unsync_page(vcpu, s);
-	}
-}
-
 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;
+	struct kvm_mmu_page *sp;
 
 	if (kvm_page_track_check_mode(vcpu, gfn, KVM_PAGE_TRACK_WRITE))
 		return true;
 
-	for_each_gfn_indirect_valid_sp(vcpu->kvm, s, gfn) {
+	for_each_gfn_indirect_valid_sp(vcpu->kvm, sp, gfn) {
 		if (!can_unsync)
 			return true;
 
-		if (s->role.level != PT_PAGE_TABLE_LEVEL)
-			return true;
+		if (sp->unsync)
+			continue;
 
-		if (!s->unsync)
-			need_unsync = true;
+		WARN_ON(sp->role.level != PT_PAGE_TABLE_LEVEL);
+		kvm_unsync_page(vcpu, sp);
 	}
-	if (need_unsync)
-		kvm_unsync_pages(vcpu, gfn);
 
 	return false;
 }
-- 
1.8.3.1