[PATCH 1/3] KVM: MMU: using kvm_set_pfn_accessed() instead of mark_page_accessed()

[PATCH 1/3] KVM: MMU: using kvm_set_pfn_accessed() instead of mark_page_accessed()

[Xiao Guangrong]

It's a small cleanup that using using kvm_set_pfn_accessed() instead
of mark_page_accessed()

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 arch/x86/kvm/mmu.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index bd82635..e10f2bd 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -313,7 +313,7 @@ static void update_spte(u64 *sptep, u64 new_spte)
 	else {
 		old_spte = __xchg_spte(sptep, new_spte);
 		if (old_spte & shadow_accessed_mask)
-			mark_page_accessed(pfn_to_page(spte_to_pfn(old_spte)));
+			kvm_set_pfn_accessed(spte_to_pfn(old_spte));
 	}
 }
 
-- 
1.6.1.2

[PATCH 2/3] KVM: MMU: move bits lost judgement into a separate function

[Xiao Guangrong]

Introduce spte_bits_lost() function to judge whether spte bits will
miss, it's more readable and can help us to cleanup code later

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 arch/x86/kvm/mmu.c |   20 +++++++++++++++++---
 1 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index e10f2bd..dd6c192 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -303,6 +303,20 @@ static u64 __xchg_spte(u64 *sptep, u64 new_spte)
 #endif
 }
 
+static bool spte_bits_lost(u64 spte)
+{
+	if (!shadow_accessed_mask)
+		return false;
+
+	if (!is_shadow_present_pte(spte))
+		return false;
+
+	if (spte & shadow_accessed_mask)
+		return false;
+
+	return true;
+}
+
 static void update_spte(u64 *sptep, u64 new_spte)
 {
 	u64 old_spte;
@@ -683,14 +697,14 @@ static void set_spte_track_bits(u64 *sptep, u64 new_spte)
 	pfn_t pfn;
 	u64 old_spte = *sptep;
 
-	if (!shadow_accessed_mask || !is_shadow_present_pte(old_spte) ||
-	      old_spte & shadow_accessed_mask) {
+	if (!spte_bits_lost(old_spte))
 		__set_spte(sptep, new_spte);
-	} else
+	else
 		old_spte = __xchg_spte(sptep, new_spte);
 
 	if (!is_rmap_spte(old_spte))
 		return;
+
 	pfn = spte_to_pfn(old_spte);
 	if (!shadow_accessed_mask || old_spte & shadow_accessed_mask)
 		kvm_set_pfn_accessed(pfn);
-- 
1.6.1.2

[PATCH 3/3] KVM: MMU: mark page dirty only when page is really written

[Xiao Guangrong]

Mark page dirty only when this page is really written, it's more exacter,
and also can fix dirty page marking in speculation path

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 arch/x86/kvm/mmu.c |   47 ++++++++++++++++++++++++++++-------------------
 1 files changed, 28 insertions(+), 19 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index dd6c192..bcc2173 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -311,24 +311,42 @@ static bool spte_bits_lost(u64 spte)
 	if (!is_shadow_present_pte(spte))
 		return false;
 
-	if (spte & shadow_accessed_mask)
+	if (spte & shadow_accessed_mask &&
+	      (!is_writable_pte(spte) || spte & shadow_dirty_mask))
 		return false;
 
 	return true;
 }
 
+static bool spte_is_bit_cleared(u64 old_spte, u64 new_spte, u64 bit_mask)
+{
+	return old_spte & bit_mask && !(new_spte & bit_mask);
+}
+
 static void update_spte(u64 *sptep, u64 new_spte)
 {
-	u64 old_spte;
+	u64 mask, old_spte = *sptep;
+
+	WARN_ON(!is_rmap_spte(new_spte));
 
-	if (!shadow_accessed_mask || (new_spte & shadow_accessed_mask) ||
-	      !is_rmap_spte(*sptep))
+	new_spte |= old_spte & shadow_dirty_mask;
+
+	mask = shadow_accessed_mask;
+	if (is_writable_pte(old_spte))
+		mask |= shadow_dirty_mask;
+
+	if (!spte_bits_lost(old_spte) || (new_spte & mask) == mask)
 		__set_spte(sptep, new_spte);
-	else {
+	else
 		old_spte = __xchg_spte(sptep, new_spte);
-		if (old_spte & shadow_accessed_mask)
-			kvm_set_pfn_accessed(spte_to_pfn(old_spte));
-	}
+
+	if (!shadow_accessed_mask)
+		return;
+
+	if (spte_is_bit_cleared(old_spte, new_spte, shadow_accessed_mask))
+		kvm_set_pfn_accessed(spte_to_pfn(old_spte));
+	if (spte_is_bit_cleared(old_spte, new_spte, shadow_dirty_mask))
+		kvm_set_pfn_dirty(spte_to_pfn(old_spte));
 }
 
 static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
@@ -708,7 +726,7 @@ static void set_spte_track_bits(u64 *sptep, u64 new_spte)
 	pfn = spte_to_pfn(old_spte);
 	if (!shadow_accessed_mask || old_spte & shadow_accessed_mask)
 		kvm_set_pfn_accessed(pfn);
-	if (is_writable_pte(old_spte))
+	if (!shadow_dirty_mask || old_spte & shadow_dirty_mask)
 		kvm_set_pfn_dirty(pfn);
 }
 
@@ -763,13 +781,6 @@ static int rmap_write_protect(struct kvm *kvm, u64 gfn)
 		}
 		spte = rmap_next(kvm, rmapp, spte);
 	}
-	if (write_protected) {
-		pfn_t pfn;
-
-		spte = rmap_next(kvm, rmapp, NULL);
-		pfn = spte_to_pfn(*spte);
-		kvm_set_pfn_dirty(pfn);
-	}
 
 	/* check for huge page mappings */
 	for (i = PT_DIRECTORY_LEVEL;
@@ -1942,7 +1953,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 	 * whether the guest actually used the pte (in order to detect
 	 * demand paging).
 	 */
-	spte = shadow_base_present_pte | shadow_dirty_mask;
+	spte = shadow_base_present_pte;
 	if (!speculative)
 		spte |= shadow_accessed_mask;
 	if (!dirty)
@@ -2003,8 +2014,6 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 		mark_page_dirty(vcpu->kvm, gfn);
 
 set_pte:
-	if (is_writable_pte(*sptep) && !is_writable_pte(spte))
-		kvm_set_pfn_dirty(pfn);
 	update_spte(sptep, spte);
 done:
 	return ret;
-- 
1.6.1.2

Re: [PATCH 2/3] KVM: MMU: move bits lost judgement into a separate function

[Avi Kivity]

  On 07/27/2010 06:33 AM, Xiao Guangrong wrote:
> Introduce spte_bits_lost() function to judge whether spte bits will
> miss, it's more readable and can help us to cleanup code later
>
> Signed-off-by: Xiao Guangrong<xiaoguangrong@cn.fujitsu.com>
> ---
>   arch/x86/kvm/mmu.c |   20 +++++++++++++++++---
>   1 files changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index e10f2bd..dd6c192 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -303,6 +303,20 @@ static u64 __xchg_spte(u64 *sptep, u64 new_spte)
>   #endif
>   }
>
> +static bool spte_bits_lost(u64 spte)
> +{
> +	if (!shadow_accessed_mask)
> +		return false;
> +
> +	if (!is_shadow_present_pte(spte))
> +		return false;
> +
> +	if (spte&  shadow_accessed_mask)
> +		return false;
> +
> +	return true;
> +}

IMO spte_has_volatile_bits() is a clearer name, "lost" implies they are 
already gone.


-- 
error compiling committee.c: too many arguments to function

Re: [PATCH 2/3] KVM: MMU: move bits lost judgement into a separate function

[Xiao Guangrong]

Avi Kivity wrote:
>  On 07/27/2010 06:33 AM, Xiao Guangrong wrote:
>> Introduce spte_bits_lost() function to judge whether spte bits will
>> miss, it's more readable and can help us to cleanup code later
>>
>> Signed-off-by: Xiao Guangrong<xiaoguangrong@cn.fujitsu.com>
>> ---
>>   arch/x86/kvm/mmu.c |   20 +++++++++++++++++---
>>   1 files changed, 17 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
>> index e10f2bd..dd6c192 100644
>> --- a/arch/x86/kvm/mmu.c
>> +++ b/arch/x86/kvm/mmu.c
>> @@ -303,6 +303,20 @@ static u64 __xchg_spte(u64 *sptep, u64 new_spte)
>>   #endif
>>   }
>>
>> +static bool spte_bits_lost(u64 spte)
>> +{
>> +    if (!shadow_accessed_mask)
>> +        return false;
>> +
>> +    if (!is_shadow_present_pte(spte))
>> +        return false;
>> +
>> +    if (spte&  shadow_accessed_mask)
>> +        return false;
>> +
>> +    return true;
>> +}
> 
> IMO spte_has_volatile_bits() is a clearer name, "lost" implies they are
> already gone.

Yeah, it's the better name, will fix soon.
 

Re: [PATCH 3/3] KVM: MMU: mark page dirty only when page is really written

[Avi Kivity]

  On 07/27/2010 06:35 AM, Xiao Guangrong wrote:
> Mark page dirty only when this page is really written, it's more exacter,
> and also can fix dirty page marking in speculation path
>
> Signed-off-by: Xiao Guangrong<xiaoguangrong@cn.fujitsu.com>
> ---
>   arch/x86/kvm/mmu.c |   47 ++++++++++++++++++++++++++++-------------------
>   1 files changed, 28 insertions(+), 19 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index dd6c192..bcc2173 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -311,24 +311,42 @@ static bool spte_bits_lost(u64 spte)
>   	if (!is_shadow_present_pte(spte))
>   		return false;
>
> -	if (spte&  shadow_accessed_mask)
> +	if (spte&  shadow_accessed_mask&&
> +	      (!is_writable_pte(spte) || spte&  shadow_dirty_mask))
>   		return false;
>

Please add parentheses around bitwise operators to reduce confusion.  
The rest looks good.

-- 
error compiling committee.c: too many arguments to function

Re: [PATCH 3/3] KVM: MMU: mark page dirty only when page is really written

[Xiao Guangrong]

Avi Kivity wrote:
>  On 07/27/2010 06:35 AM, Xiao Guangrong wrote:
>> Mark page dirty only when this page is really written, it's more exacter,
>> and also can fix dirty page marking in speculation path
>>
>> Signed-off-by: Xiao Guangrong<xiaoguangrong@cn.fujitsu.com>
>> ---
>>   arch/x86/kvm/mmu.c |   47
>> ++++++++++++++++++++++++++++-------------------
>>   1 files changed, 28 insertions(+), 19 deletions(-)
>>
>> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
>> index dd6c192..bcc2173 100644
>> --- a/arch/x86/kvm/mmu.c
>> +++ b/arch/x86/kvm/mmu.c
>> @@ -311,24 +311,42 @@ static bool spte_bits_lost(u64 spte)
>>       if (!is_shadow_present_pte(spte))
>>           return false;
>>
>> -    if (spte&  shadow_accessed_mask)
>> +    if (spte&  shadow_accessed_mask&&
>> +          (!is_writable_pte(spte) || spte&  shadow_dirty_mask))
>>           return false;
>>
> 
> Please add parentheses around bitwise operators to reduce confusion. 
> The rest looks good.
> 

OK, will do it in the new version, thanks.

[PATCH v2 1/3] KVM: MMU: using kvm_set_pfn_accessed() instead of mark_page_accessed()

[Xiao Guangrong]

It's a small cleanup that using using kvm_set_pfn_accessed() instead
of mark_page_accessed()

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 arch/x86/kvm/mmu.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 56da796..f7b379a 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -313,7 +313,7 @@ static void update_spte(u64 *sptep, u64 new_spte)
 	else {
 		old_spte = __xchg_spte(sptep, new_spte);
 		if (old_spte & shadow_accessed_mask)
-			mark_page_accessed(pfn_to_page(spte_to_pfn(old_spte)));
+			kvm_set_pfn_accessed(spte_to_pfn(old_spte));
 	}
 }
 
-- 
1.6.1.2

[PATCH v2 2/3] KVM: MMU: move bits lost judgement into a separate function

[Xiao Guangrong]

Introduce spte_has_volatile_bits() function to judge whether spte
bits will miss, it's more readable and can help us to cleanup code
later

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 arch/x86/kvm/mmu.c |   20 +++++++++++++++++---
 1 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index f7b379a..e18834c 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -303,6 +303,20 @@ static u64 __xchg_spte(u64 *sptep, u64 new_spte)
 #endif
 }
 
+static bool spte_has_volatile_bits(u64 spte)
+{
+	if (!shadow_accessed_mask)
+		return false;
+
+	if (!is_shadow_present_pte(spte))
+		return false;
+
+	if (spte & shadow_accessed_mask)
+		return false;
+
+	return true;
+}
+
 static void update_spte(u64 *sptep, u64 new_spte)
 {
 	u64 old_spte;
@@ -683,14 +697,14 @@ static void set_spte_track_bits(u64 *sptep, u64 new_spte)
 	pfn_t pfn;
 	u64 old_spte = *sptep;
 
-	if (!shadow_accessed_mask || !is_shadow_present_pte(old_spte) ||
-	      old_spte & shadow_accessed_mask) {
+	if (!spte_has_volatile_bits(old_spte))
 		__set_spte(sptep, new_spte);
-	} else
+	else
 		old_spte = __xchg_spte(sptep, new_spte);
 
 	if (!is_rmap_spte(old_spte))
 		return;
+
 	pfn = spte_to_pfn(old_spte);
 	if (!shadow_accessed_mask || old_spte & shadow_accessed_mask)
 		kvm_set_pfn_accessed(pfn);
-- 
1.6.1.2

[PATCH v2 3/3] KVM: MMU: mark page dirty only when page is really written

[Xiao Guangrong]

Mark page dirty only when this page is really written, it's more exacter,
and also can fix dirty page marking in speculation path

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 arch/x86/kvm/mmu.c |   47 ++++++++++++++++++++++++++++-------------------
 1 files changed, 28 insertions(+), 19 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index e18834c..9c69725 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -311,24 +311,42 @@ static bool spte_has_volatile_bits(u64 spte)
 	if (!is_shadow_present_pte(spte))
 		return false;
 
-	if (spte & shadow_accessed_mask)
+	if ((spte & shadow_accessed_mask) &&
+	      (!is_writable_pte(spte) || (spte & shadow_dirty_mask)))
 		return false;
 
 	return true;
 }
 
+static bool spte_is_bit_cleared(u64 old_spte, u64 new_spte, u64 bit_mask)
+{
+	return (old_spte & bit_mask) && !(new_spte & bit_mask);
+}
+
 static void update_spte(u64 *sptep, u64 new_spte)
 {
-	u64 old_spte;
+	u64 mask, old_spte = *sptep;
+
+	WARN_ON(!is_rmap_spte(new_spte));
 
-	if (!shadow_accessed_mask || (new_spte & shadow_accessed_mask) ||
-	      !is_rmap_spte(*sptep))
+	new_spte |= old_spte & shadow_dirty_mask;
+
+	mask = shadow_accessed_mask;
+	if (is_writable_pte(old_spte))
+		mask |= shadow_dirty_mask;
+
+	if (!spte_has_volatile_bits(old_spte) || (new_spte & mask) == mask)
 		__set_spte(sptep, new_spte);
-	else {
+	else
 		old_spte = __xchg_spte(sptep, new_spte);
-		if (old_spte & shadow_accessed_mask)
-			kvm_set_pfn_accessed(spte_to_pfn(old_spte));
-	}
+
+	if (!shadow_accessed_mask)
+		return;
+
+	if (spte_is_bit_cleared(old_spte, new_spte, shadow_accessed_mask))
+		kvm_set_pfn_accessed(spte_to_pfn(old_spte));
+	if (spte_is_bit_cleared(old_spte, new_spte, shadow_dirty_mask))
+		kvm_set_pfn_dirty(spte_to_pfn(old_spte));
 }
 
 static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
@@ -708,7 +726,7 @@ static void set_spte_track_bits(u64 *sptep, u64 new_spte)
 	pfn = spte_to_pfn(old_spte);
 	if (!shadow_accessed_mask || old_spte & shadow_accessed_mask)
 		kvm_set_pfn_accessed(pfn);
-	if (is_writable_pte(old_spte))
+	if (!shadow_dirty_mask || (old_spte & shadow_dirty_mask))
 		kvm_set_pfn_dirty(pfn);
 }
 
@@ -763,13 +781,6 @@ static int rmap_write_protect(struct kvm *kvm, u64 gfn)
 		}
 		spte = rmap_next(kvm, rmapp, spte);
 	}
-	if (write_protected) {
-		pfn_t pfn;
-
-		spte = rmap_next(kvm, rmapp, NULL);
-		pfn = spte_to_pfn(*spte);
-		kvm_set_pfn_dirty(pfn);
-	}
 
 	/* check for huge page mappings */
 	for (i = PT_DIRECTORY_LEVEL;
@@ -1942,7 +1953,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 	 * whether the guest actually used the pte (in order to detect
 	 * demand paging).
 	 */
-	spte = shadow_base_present_pte | shadow_dirty_mask;
+	spte = shadow_base_present_pte;
 	if (!speculative)
 		spte |= shadow_accessed_mask;
 	if (!dirty)
@@ -2003,8 +2014,6 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 		mark_page_dirty(vcpu->kvm, gfn);
 
 set_pte:
-	if (is_writable_pte(*sptep) && !is_writable_pte(spte))
-		kvm_set_pfn_dirty(pfn);
 	update_spte(sptep, spte);
 done:
 	return ret;
-- 
1.6.1.2

Re: [PATCH v2 1/3] KVM: MMU: using kvm_set_pfn_accessed() instead of mark_page_accessed()

[Avi Kivity]

  On 08/02/2010 11:12 AM, Xiao Guangrong wrote:
> It's a small cleanup that using using kvm_set_pfn_accessed() instead
> of mark_page_accessed()

Applied all of v2, thanks.

-- 
error compiling committee.c: too many arguments to function