[PATCH 1/2] KVM MMU: fix for forgot mark parent->unsync_children bit

[PATCH 1/2] KVM MMU: fix for forgot mark parent->unsync_children bit

[Xiao Guangrong]

When mapping a new parent to unsync shadow page, we should mark
parent's unsync_children bit

Reported-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 arch/x86/kvm/mmu.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 97f2ea0..bf35a2f 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1374,7 +1374,9 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
 			if (sp->unsync_children) {
 				set_bit(KVM_REQ_MMU_SYNC, &vcpu->requests);
 				kvm_mmu_mark_parents_unsync(sp);
-			}
+			} else if (sp->unsync)
+				kvm_mmu_mark_parents_unsync(sp);
+
 			trace_kvm_mmu_get_page(sp, false);
 			return sp;
 		}
-- 
1.6.1.2

[PATCH 2/2] KVM MMU: fix race in invlpg code

[Xiao Guangrong]

It has race in invlpg code, like below sequences:

A: hold mmu_lock and get 'sp'
B: release mmu_lock and do other things
C: hold mmu_lock and continue use 'sp'

if other path freed 'sp' in stage B, then kernel will crash

This patch checks 'sp' whether lived before use 'sp' in stage C

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 arch/x86/kvm/paging_tmpl.h |   22 ++++++++++++++++++++--
 1 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 624b38f..13ea675 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -462,11 +462,16 @@ out_unlock:
 
 static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)
 {
-	struct kvm_mmu_page *sp = NULL;
+	struct kvm_mmu_page *sp = NULL, *s;
 	struct kvm_shadow_walk_iterator iterator;
+	struct hlist_head *bucket;
+	struct hlist_node *node, *tmp;
 	gfn_t gfn = -1;
 	u64 *sptep = NULL, gentry;
 	int invlpg_counter, level, offset = 0, need_flush = 0;
+	unsigned index;
+	bool live = false;
+	union kvm_mmu_page_role role;
 
 	spin_lock(&vcpu->kvm->mmu_lock);
 
@@ -480,7 +485,7 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)
 
 			if (!sp->unsync)
 				break;
-
+			role = sp->role;
 			WARN_ON(level != PT_PAGE_TABLE_LEVEL);
 			shift = PAGE_SHIFT -
 				  (PT_LEVEL_BITS - PT64_LEVEL_BITS) * level;
@@ -519,10 +524,23 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)
 
 	mmu_guess_page_from_pte_write(vcpu, gfn_to_gpa(gfn) + offset, gentry);
 	spin_lock(&vcpu->kvm->mmu_lock);
+	index = kvm_page_table_hashfn(gfn);
+	bucket = &vcpu->kvm->arch.mmu_page_hash[index];
+	hlist_for_each_entry_safe(s, node, tmp, bucket, hash_link)
+		if (s == sp) {
+			if (s->gfn == gfn && s->role.word == role.word)
+				live = true;
+			break;
+		}
+
+	if (!live)
+		goto unlock_exit;
+
 	if (atomic_read(&vcpu->kvm->arch.invlpg_counter) == invlpg_counter) {
 		++vcpu->kvm->stat.mmu_pte_updated;
 		FNAME(update_pte)(vcpu, sp, sptep, &gentry);
 	}
+unlock_exit:
 	spin_unlock(&vcpu->kvm->mmu_lock);
 	mmu_release_page_from_pte_write(vcpu);
 }
-- 
1.6.1.2

Re: [PATCH 2/2] KVM MMU: fix race in invlpg code

[Avi Kivity]

On 05/05/2010 03:21 PM, Xiao Guangrong wrote:
> It has race in invlpg code, like below sequences:
>
> A: hold mmu_lock and get 'sp'
> B: release mmu_lock and do other things
> C: hold mmu_lock and continue use 'sp'
>
> if other path freed 'sp' in stage B, then kernel will crash
>
> This patch checks 'sp' whether lived before use 'sp' in stage C
>
> Signed-off-by: Xiao Guangrong<xiaoguangrong@cn.fujitsu.com>
> ---
>   arch/x86/kvm/paging_tmpl.h |   22 ++++++++++++++++++++--
>   1 files changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
> index 624b38f..13ea675 100644
> --- a/arch/x86/kvm/paging_tmpl.h
> +++ b/arch/x86/kvm/paging_tmpl.h
> @@ -462,11 +462,16 @@ out_unlock:
>
>   static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)
>   {
> -	struct kvm_mmu_page *sp = NULL;
> +	struct kvm_mmu_page *sp = NULL, *s;
>   	struct kvm_shadow_walk_iterator iterator;
> +	struct hlist_head *bucket;
> +	struct hlist_node *node, *tmp;
>   	gfn_t gfn = -1;
>   	u64 *sptep = NULL, gentry;
>   	int invlpg_counter, level, offset = 0, need_flush = 0;
> +	unsigned index;
> +	bool live = false;
> +	union kvm_mmu_page_role role;
>
>   	spin_lock(&vcpu->kvm->mmu_lock);
>
> @@ -480,7 +485,7 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)
>
>   			if (!sp->unsync)
>   				break;
> -
> +			role = sp->role;
>   			WARN_ON(level != PT_PAGE_TABLE_LEVEL);
>   			shift = PAGE_SHIFT -
>   				  (PT_LEVEL_BITS - PT64_LEVEL_BITS) * level;
> @@ -519,10 +524,23 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)
>
>   	mmu_guess_page_from_pte_write(vcpu, gfn_to_gpa(gfn) + offset, gentry);
>   	spin_lock(&vcpu->kvm->mmu_lock);
> +	index = kvm_page_table_hashfn(gfn);
> +	bucket =&vcpu->kvm->arch.mmu_page_hash[index];
> +	hlist_for_each_entry_safe(s, node, tmp, bucket, hash_link)
> +		if (s == sp) {
> +			if (s->gfn == gfn&&  s->role.word == role.word)
> +				live = true;
> +			break;
> +		}
> +
> +	if (!live)
> +		goto unlock_exit;
> +
>    

Did you try the root_count method?  I think it's cleaner.

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

Re: [PATCH 2/2] KVM MMU: fix race in invlpg code

[Xiao Guangrong]

Avi Kivity wrote:

>>       spin_lock(&vcpu->kvm->mmu_lock);
>> +    index = kvm_page_table_hashfn(gfn);
>> +    bucket =&vcpu->kvm->arch.mmu_page_hash[index];
>> +    hlist_for_each_entry_safe(s, node, tmp, bucket, hash_link)
>> +        if (s == sp) {
>> +            if (s->gfn == gfn&&  s->role.word == role.word)
>> +                live = true;
>> +            break;
>> +        }
>> +
>> +    if (!live)
>> +        goto unlock_exit;
>> +
>>    
> 
> Did you try the root_count method?  I think it's cleaner.

Avi, Thanks for your idea.

I have considered this method, but i'm not sure when it's the good time
to real free this page, and i think we also need a way to synchronize the
real free path and this path. Do you have any comment for it :-(

Xiao

Re: [PATCH 2/2] KVM MMU: fix race in invlpg code

[Avi Kivity]

On 05/05/2010 03:45 PM, Xiao Guangrong wrote:
>
> Avi Kivity wrote:
>
>    
>>>        spin_lock(&vcpu->kvm->mmu_lock);
>>> +    index = kvm_page_table_hashfn(gfn);
>>> +    bucket =&vcpu->kvm->arch.mmu_page_hash[index];
>>> +    hlist_for_each_entry_safe(s, node, tmp, bucket, hash_link)
>>> +        if (s == sp) {
>>> +            if (s->gfn == gfn&&   s->role.word == role.word)
>>> +                live = true;
>>> +            break;
>>> +        }
>>> +
>>> +    if (!live)
>>> +        goto unlock_exit;
>>> +
>>>
>>>        
>> Did you try the root_count method?  I think it's cleaner.
>>      
> Avi, Thanks for your idea.
>
> I have considered this method, but i'm not sure when it's the good time
> to real free this page, and i think we also need a way to synchronize the
> real free path and this path. Do you have any comment for it :-(
>    

Same as mmu_free_roots():

         --sp->root_count;
         if (!sp->root_count && sp->role.invalid) {
                 kvm_mmu_zap_page(vcpu->kvm, sp);
                 goto unlock_exit;
         }


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

Re: [PATCH 1/2] KVM MMU: fix for forgot mark parent->unsync_children bit

[Avi Kivity]

On 05/05/2010 03:19 PM, Xiao Guangrong wrote:
> When mapping a new parent to unsync shadow page, we should mark
> parent's unsync_children bit
>
> Reported-by: Marcelo Tosatti<mtosatti@redhat.com>
> Signed-off-by: Xiao Guangrong<xiaoguangrong@cn.fujitsu.com>
> ---
>   arch/x86/kvm/mmu.c |    4 +++-
>   1 files changed, 3 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 97f2ea0..bf35a2f 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -1374,7 +1374,9 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
>   			if (sp->unsync_children) {
>   				set_bit(KVM_REQ_MMU_SYNC,&vcpu->requests);
>   				kvm_mmu_mark_parents_unsync(sp);
> -			}
> +			} else if (sp->unsync)
> +				kvm_mmu_mark_parents_unsync(sp);
> +
>   			trace_kvm_mmu_get_page(sp, false);
>   			return sp;
>   		}
>    


Which patch does this fix?  If it wasn't merge yet, please repost with 
the fix included.

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

Re: [PATCH 1/2] KVM MMU: fix for forgot mark parent->unsync_children bit

[Xiao Guangrong]

Avi Kivity wrote:
> On 05/05/2010 03:19 PM, Xiao Guangrong wrote:
>> When mapping a new parent to unsync shadow page, we should mark
>> parent's unsync_children bit
>>
>> Reported-by: Marcelo Tosatti<mtosatti@redhat.com>
>> Signed-off-by: Xiao Guangrong<xiaoguangrong@cn.fujitsu.com>
>> ---
>>   arch/x86/kvm/mmu.c |    4 +++-
>>   1 files changed, 3 insertions(+), 1 deletions(-)
>>
>> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
>> index 97f2ea0..bf35a2f 100644
>> --- a/arch/x86/kvm/mmu.c
>> +++ b/arch/x86/kvm/mmu.c
>> @@ -1374,7 +1374,9 @@ static struct kvm_mmu_page
>> *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
>>               if (sp->unsync_children) {
>>                   set_bit(KVM_REQ_MMU_SYNC,&vcpu->requests);
>>                   kvm_mmu_mark_parents_unsync(sp);
>> -            }
>> +            } else if (sp->unsync)
>> +                kvm_mmu_mark_parents_unsync(sp);
>> +
>>               trace_kvm_mmu_get_page(sp, false);
>>               return sp;
>>           }
>>    
> 
> 
> Which patch does this fix?  If it wasn't merge yet, please repost with
> the fix included.

Oh, OK, i'll sent the previous pathset that are reverted by Marcelo.

Thanks,
Xiao