subject:"\[PATCH 4\/8\] KVM\: avoid unnecessary wait for a async pf"

Re: [PATCH 4/8] KVM: avoid unnecessary wait for a async pf

2010-10-28 Thread Xiao Guangrong

On 10/27/2010 06:42 PM, Gleb Natapov wrote:
> On Wed, Oct 27, 2010 at 05:04:58PM +0800, Xiao Guangrong wrote:
>> In current code, it checks async pf completion out of the wait context,
>> like this:
>>
>> if (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE &&
>>  !vcpu->arch.apf.halted)
>>  r = vcpu_enter_guest(vcpu);
>>  else {
>>  ..
>>  kvm_vcpu_block(vcpu)
>>   ^- waiting until 'async_pf.done' is not empty
>> }
>>  
>> kvm_check_async_pf_completion(vcpu)
>>  ^- delete list from async_pf.done
>>
>> So, if we check aysnc pf completion first, it can be blocked at
>> kvm_vcpu_block
>>
> Correct, but it can be fixed by adding vcpu->arch.apf.halted = false; to
> kvm_arch_async_page_present(), no?
> Adding kvm_check_async_pf_completion() to arch independent kvm_vcpu_block()
> constrains how other archs may implement async pf support IMO.
>  

Um, i think it's reasonable, will fix it address your comment.
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Re: [PATCH 4/8] KVM: avoid unnecessary wait for a async pf

2010-10-27 Thread Gleb Natapov

On Wed, Oct 27, 2010 at 05:04:58PM +0800, Xiao Guangrong wrote:
> In current code, it checks async pf completion out of the wait context,
> like this:
> 
> if (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE &&
>   !vcpu->arch.apf.halted)
>   r = vcpu_enter_guest(vcpu);
>   else {
>   ..
>   kvm_vcpu_block(vcpu)
>^- waiting until 'async_pf.done' is not empty
> }
>   
> kvm_check_async_pf_completion(vcpu)
>  ^- delete list from async_pf.done
> 
> So, if we check aysnc pf completion first, it can be blocked at
> kvm_vcpu_block
> 
Correct, but it can be fixed by adding vcpu->arch.apf.halted = false; to
kvm_arch_async_page_present(), no?
Adding kvm_check_async_pf_completion() to arch independent kvm_vcpu_block()
constrains how other archs may implement async pf support IMO.
 
> Fixed by move the check into wait context
> 
> Signed-off-by: Xiao Guangrong 
> ---
>  arch/x86/kvm/x86.c   |3 ---
>  include/linux/kvm_host.h |1 -
>  virt/kvm/async_pf.c  |6 --
>  virt/kvm/async_pf.h  |6 ++
>  virt/kvm/kvm_main.c  |3 ++-
>  5 files changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 16f42ff..0b2c420 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5321,8 +5321,6 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
>   vcpu->run->exit_reason = KVM_EXIT_INTR;
>   ++vcpu->stat.request_irq_exits;
>   }
> - 
> - kvm_check_async_pf_completion(vcpu);
>  
>   if (signal_pending(current)) {
>   r = -EINTR;
> @@ -6108,7 +6106,6 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
>  {
>   return (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE &&
>   !vcpu->arch.apf.halted)
> - || !list_empty_careful(&vcpu->async_pf.done)
>   || vcpu->arch.mp_state == KVM_MP_STATE_SIPI_RECEIVED
>   || vcpu->arch.nmi_pending ||
>   (kvm_arch_interrupt_allowed(vcpu) &&
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index ee4314e..0c1b7c5 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -90,7 +90,6 @@ struct kvm_async_pf {
>  };
>  
>  void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu);
> -void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu);
>  int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn,
>  struct kvm_arch_async_pf *arch);
>  int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu);
> diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
> index 60df9e0..e213ca4 100644
> --- a/virt/kvm/async_pf.c
> +++ b/virt/kvm/async_pf.c
> @@ -120,13 +120,13 @@ void kvm_clear_async_pf_completion_queue(struct 
> kvm_vcpu *vcpu)
>   vcpu->async_pf.queued = 0;
>  }
>  
> -void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
> +bool kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
>  {
>   struct kvm_async_pf *work;
>  
>   if (list_empty_careful(&vcpu->async_pf.done) ||
>   !kvm_arch_can_inject_async_page_present(vcpu))
> - return;
> + return false;
>  
>   spin_lock(&vcpu->async_pf.lock);
>   work = list_first_entry(&vcpu->async_pf.done, typeof(*work), link);
> @@ -142,6 +142,8 @@ void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
>   if (work->page)
>   put_page(work->page);
>   kmem_cache_free(async_pf_cache, work);
> +
> + return true;
>  }
>  
>  int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn,
> diff --git a/virt/kvm/async_pf.h b/virt/kvm/async_pf.h
> index e7ef644..e21533c 100644
> --- a/virt/kvm/async_pf.h
> +++ b/virt/kvm/async_pf.h
> @@ -27,10 +27,16 @@
>  int kvm_async_pf_init(void);
>  void kvm_async_pf_deinit(void);
>  void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu);
> +bool kvm_check_async_pf_completion(struct kvm_vcpu *vcpu);
> +
>  #else
>  #define kvm_async_pf_init() (0)
>  #define kvm_async_pf_deinit() do{}while(0)
>  #define kvm_async_pf_vcpu_init(C) do{}while(0)
> +static inline bool kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
> +{
> + return false;
> +}
>  #endif
>  
>  #endif
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 88d869e..d9aed28 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1347,7 +1347,8 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
>   for (;;) {
>   prepare_to_wait(&vcpu->wq, &wait, TASK_INTERRUPTIBLE);
>  
> - if (kvm_arch_vcpu_runnable(vcpu)) {
> + if (kvm_arch_vcpu_runnable(vcpu) ||
> +  kvm_check_async_pf_completion(vcpu)) {
>   kvm_make_request(KVM_REQ_UNHALT, vcpu);
>   break;
>   }
> -- 
> 1.7.0.4
> 
> --
> To unsubscribe from this list: send the line "un

[PATCH 4/8] KVM: avoid unnecessary wait for a async pf

2010-10-27 Thread Xiao Guangrong

In current code, it checks async pf completion out of the wait context,
like this:

if (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE &&
!vcpu->arch.apf.halted)
r = vcpu_enter_guest(vcpu);
else {
..
kvm_vcpu_block(vcpu)
 ^- waiting until 'async_pf.done' is not empty
}

kvm_check_async_pf_completion(vcpu)
 ^- delete list from async_pf.done

So, if we check aysnc pf completion first, it can be blocked at
kvm_vcpu_block

Fixed by move the check into wait context

Signed-off-by: Xiao Guangrong 
---
 arch/x86/kvm/x86.c   |3 ---
 include/linux/kvm_host.h |1 -
 virt/kvm/async_pf.c  |6 --
 virt/kvm/async_pf.h  |6 ++
 virt/kvm/kvm_main.c  |3 ++-
 5 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 16f42ff..0b2c420 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5321,8 +5321,6 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
vcpu->run->exit_reason = KVM_EXIT_INTR;
++vcpu->stat.request_irq_exits;
}
-   
-   kvm_check_async_pf_completion(vcpu);
 
if (signal_pending(current)) {
r = -EINTR;
@@ -6108,7 +6106,6 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
 {
return (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE &&
!vcpu->arch.apf.halted)
-   || !list_empty_careful(&vcpu->async_pf.done)
|| vcpu->arch.mp_state == KVM_MP_STATE_SIPI_RECEIVED
|| vcpu->arch.nmi_pending ||
(kvm_arch_interrupt_allowed(vcpu) &&
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index ee4314e..0c1b7c5 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -90,7 +90,6 @@ struct kvm_async_pf {
 };
 
 void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu);
-void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu);
 int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn,
   struct kvm_arch_async_pf *arch);
 int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu);
diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
index 60df9e0..e213ca4 100644
--- a/virt/kvm/async_pf.c
+++ b/virt/kvm/async_pf.c
@@ -120,13 +120,13 @@ void kvm_clear_async_pf_completion_queue(struct kvm_vcpu 
*vcpu)
vcpu->async_pf.queued = 0;
 }
 
-void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
+bool kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
 {
struct kvm_async_pf *work;
 
if (list_empty_careful(&vcpu->async_pf.done) ||
!kvm_arch_can_inject_async_page_present(vcpu))
-   return;
+   return false;
 
spin_lock(&vcpu->async_pf.lock);
work = list_first_entry(&vcpu->async_pf.done, typeof(*work), link);
@@ -142,6 +142,8 @@ void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
if (work->page)
put_page(work->page);
kmem_cache_free(async_pf_cache, work);
+
+   return true;
 }
 
 int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn,
diff --git a/virt/kvm/async_pf.h b/virt/kvm/async_pf.h
index e7ef644..e21533c 100644
--- a/virt/kvm/async_pf.h
+++ b/virt/kvm/async_pf.h
@@ -27,10 +27,16 @@
 int kvm_async_pf_init(void);
 void kvm_async_pf_deinit(void);
 void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu);
+bool kvm_check_async_pf_completion(struct kvm_vcpu *vcpu);
+
 #else
 #define kvm_async_pf_init() (0)
 #define kvm_async_pf_deinit() do{}while(0)
 #define kvm_async_pf_vcpu_init(C) do{}while(0)
+static inline bool kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
+{
+   return false;
+}
 #endif
 
 #endif
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 88d869e..d9aed28 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1347,7 +1347,8 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
for (;;) {
prepare_to_wait(&vcpu->wq, &wait, TASK_INTERRUPTIBLE);
 
-   if (kvm_arch_vcpu_runnable(vcpu)) {
+   if (kvm_arch_vcpu_runnable(vcpu) ||
+kvm_check_async_pf_completion(vcpu)) {
kvm_make_request(KVM_REQ_UNHALT, vcpu);
break;
}
-- 
1.7.0.4

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Re: [PATCH 4/8] KVM: avoid unnecessary wait for a async pf

Re: [PATCH 4/8] KVM: avoid unnecessary wait for a async pf

[PATCH 4/8] KVM: avoid unnecessary wait for a async pf

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