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[PATCH v2 1/4] KVM: add spinlock optimization framework

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  [PATCH v2 1/4] KVM: add spinlock optimization framework "Longpeng(Mike)" <longpeng2@huawei.com> - 2017-08-08 06:10 +0200
    Re: [PATCH v2 1/4] KVM: add spinlock optimization framework Paolo Bonzini <pbonzini@redhat.com> - 2017-08-08 09:40 +0200
      Re: [PATCH v2 1/4] KVM: add spinlock optimization framework Cornelia Huck <cohuck@redhat.com> - 2017-08-08 09:50 +0200
    Re: [PATCH v2 1/4] KVM: add spinlock optimization framework David Hildenbrand <david@redhat.com> - 2017-08-08 10:50 +0200
    Re: [PATCH v2 1/4] KVM: add spinlock optimization framework David Hildenbrand <david@redhat.com> - 2017-08-08 10:50 +0200
      Re: [PATCH v2 1/4] KVM: add spinlock optimization framework Paolo Bonzini <pbonzini@redhat.com> - 2017-08-08 11:10 +0200
        Re: [PATCH v2 1/4] KVM: add spinlock optimization framework "Longpeng (Mike)" <longpeng2@huawei.com> - 2017-08-08 11:40 +0200

#1705993 — [PATCH v2 1/4] KVM: add spinlock optimization framework

If the vcpu(me) exit due to request a usermode spinlock, then
the spinlock-holder may be preempted in usermode or kernmode.

But if the vcpu(me) is in kernmode, then the holder must be
preempted in kernmode, so we should choose a vcpu in kernmode
as the most eligible candidate.

This introduces kvm_arch_vcpu_in_kernel() to decide whether the
vcpu is in kernel-mode when it's preempted or spinlock exit.

Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com>
---
 arch/arm/kvm/handle_exit.c   | 2 +-
 arch/arm64/kvm/handle_exit.c | 2 +-
 arch/mips/kvm/mips.c         | 6 ++++++
 arch/powerpc/kvm/powerpc.c   | 6 ++++++
 arch/s390/kvm/diag.c         | 2 +-
 arch/s390/kvm/kvm-s390.c     | 6 ++++++
 arch/x86/kvm/hyperv.c        | 2 +-
 arch/x86/kvm/svm.c           | 4 +++-
 arch/x86/kvm/vmx.c           | 2 +-
 arch/x86/kvm/x86.c           | 6 ++++++
 include/linux/kvm_host.h     | 3 ++-
 virt/kvm/arm/arm.c           | 5 +++++
 virt/kvm/kvm_main.c          | 4 +++-
 13 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/arch/arm/kvm/handle_exit.c b/arch/arm/kvm/handle_exit.c
index 54442e3..a7ea5db 100644
--- a/arch/arm/kvm/handle_exit.c
+++ b/arch/arm/kvm/handle_exit.c
@@ -67,7 +67,7 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
 	if (kvm_vcpu_get_hsr(vcpu) & HSR_WFI_IS_WFE) {
 		trace_kvm_wfx(*vcpu_pc(vcpu), true);
 		vcpu->stat.wfe_exit_stat++;
-		kvm_vcpu_on_spin(vcpu);
+		kvm_vcpu_on_spin(vcpu, kvm_arch_vcpu_in_kernel(vcpu));
 	} else {
 		trace_kvm_wfx(*vcpu_pc(vcpu), false);
 		vcpu->stat.wfi_exit_stat++;
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 17d8a16..d6c8cb6 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -84,7 +84,7 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
 	if (kvm_vcpu_get_hsr(vcpu) & ESR_ELx_WFx_ISS_WFE) {
 		trace_kvm_wfx_arm64(*vcpu_pc(vcpu), true);
 		vcpu->stat.wfe_exit_stat++;
-		kvm_vcpu_on_spin(vcpu);
+		kvm_vcpu_on_spin(vcpu, kvm_arch_vcpu_in_kernel(vcpu));
 	} else {
 		trace_kvm_wfx_arm64(*vcpu_pc(vcpu), false);
 		vcpu->stat.wfi_exit_stat++;
diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index d4b2ad1..70208be 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -98,6 +98,12 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
 	return !!(vcpu->arch.pending_exceptions);
 }
 
+bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
+{
+	return false;
+}
+EXPORT_SYMBOL_GPL(kvm_arch_vcpu_in_kernel);
+
 int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
 {
 	return 1;
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 1a75c0b..6184c45 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -58,6 +58,12 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *v)
 	return !!(v->arch.pending_exceptions) || kvm_request_pending(v);
 }
 
+bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
+{
+	return false;
+}
+EXPORT_SYMBOL_GPL(kvm_arch_vcpu_in_kernel);
+
 int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
 {
 	return 1;
diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
index ce865bd..4ea8c38 100644
--- a/arch/s390/kvm/diag.c
+++ b/arch/s390/kvm/diag.c
@@ -150,7 +150,7 @@ static int __diag_time_slice_end(struct kvm_vcpu *vcpu)
 {
 	VCPU_EVENT(vcpu, 5, "%s", "diag time slice end");
 	vcpu->stat.diagnose_44++;
-	kvm_vcpu_on_spin(vcpu);
+	kvm_vcpu_on_spin(vcpu, kvm_arch_vcpu_in_kernel(vcpu));
 	return 0;
 }
 
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index af09d34..0b0c689 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2447,6 +2447,12 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
 	return kvm_s390_vcpu_has_irq(vcpu, 0);
 }
 
+bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
+{
+	return false;
+}
+EXPORT_SYMBOL_GPL(kvm_arch_vcpu_in_kernel);
+
 void kvm_s390_vcpu_block(struct kvm_vcpu *vcpu)
 {
 	atomic_or(PROG_BLOCK_SIE, &vcpu->arch.sie_block->prog20);
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 337b6d2..cd0e6e6 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1268,7 +1268,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 
 	switch (code) {
 	case HVCALL_NOTIFY_LONG_SPIN_WAIT:
-		kvm_vcpu_on_spin(vcpu);
+		kvm_vcpu_on_spin(vcpu, kvm_arch_vcpu_in_kernel(vcpu));
 		break;
 	case HVCALL_POST_MESSAGE:
 	case HVCALL_SIGNAL_EVENT:
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 1107626..e6ed24e 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -3749,7 +3749,9 @@ static int interrupt_window_interception(struct vcpu_svm *svm)
 
 static int pause_interception(struct vcpu_svm *svm)
 {
-	kvm_vcpu_on_spin(&(svm->vcpu));
+	struct kvm_vcpu *vcpu = &(svm->vcpu);
+
+	kvm_vcpu_on_spin(vcpu, kvm_arch_vcpu_in_kernel(vcpu));
 	return 1;
 }
 
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 9b21b12..9d6223a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6761,7 +6761,7 @@ static int handle_pause(struct kvm_vcpu *vcpu)
 	if (ple_gap)
 		grow_ple_window(vcpu);
 
-	kvm_vcpu_on_spin(vcpu);
+	kvm_vcpu_on_spin(vcpu, kvm_arch_vcpu_in_kernel(vcpu));
 	return kvm_skip_emulated_instruction(vcpu);
 }
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d734aa8..4430be6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8439,6 +8439,12 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
 	return kvm_vcpu_running(vcpu) || kvm_vcpu_has_events(vcpu);
 }
 
+bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
+{
+	return false;
+}
+EXPORT_SYMBOL_GPL(kvm_arch_vcpu_in_kernel);
+
 int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
 {
 	return kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 21a6fd6..91460aa 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -720,7 +720,7 @@ int kvm_vcpu_write_guest(struct kvm_vcpu *vcpu, gpa_t gpa, const void *data,
 bool kvm_vcpu_wake_up(struct kvm_vcpu *vcpu);
 void kvm_vcpu_kick(struct kvm_vcpu *vcpu);
 int kvm_vcpu_yield_to(struct kvm_vcpu *target);
-void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu);
+void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu, bool me_in_kern);
 void kvm_load_guest_fpu(struct kvm_vcpu *vcpu);
 void kvm_put_guest_fpu(struct kvm_vcpu *vcpu);
 
@@ -800,6 +800,7 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
 void kvm_arch_hardware_unsetup(void);
 void kvm_arch_check_processor_compat(void *rtn);
 int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu);
+bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu);
 int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu);
 
 #ifndef __KVM_HAVE_ARCH_VM_ALLOC
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index a39a1e1..862f820 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -416,6 +416,11 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *v)
 		&& !v->arch.power_off && !v->arch.pause);
 }
 
+bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
+{
+	return false;
+}
+
 /* Just ensure a guest exit from a particular CPU */
 static void exit_vm_noop(void *info)
 {
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 15252d7..e7720d2 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2317,7 +2317,7 @@ static bool kvm_vcpu_eligible_for_directed_yield(struct kvm_vcpu *vcpu)
 #endif
 }
 
-void kvm_vcpu_on_spin(struct kvm_vcpu *me)
+void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool me_in_kern)
 {
 	struct kvm *kvm = me->kvm;
 	struct kvm_vcpu *vcpu;
@@ -2348,6 +2348,8 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
 				continue;
 			if (swait_active(&vcpu->wq) && !kvm_arch_vcpu_runnable(vcpu))
 				continue;
+			if (me_in_kern && !kvm_arch_vcpu_in_kernel(vcpu))
+				continue;
 			if (!kvm_vcpu_eligible_for_directed_yield(vcpu))
 				continue;
 
-- 
1.8.3.1

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#1706107

On 08/08/2017 06:05, Longpeng(Mike) wrote:
>  	return 1;
> diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
> index ce865bd..4ea8c38 100644
> --- a/arch/s390/kvm/diag.c
> +++ b/arch/s390/kvm/diag.c
> @@ -150,7 +150,7 @@ static int __diag_time_slice_end(struct kvm_vcpu *vcpu)
>  {
>  	VCPU_EVENT(vcpu, 5, "%s", "diag time slice end");
>  	vcpu->stat.diagnose_44++;
> -	kvm_vcpu_on_spin(vcpu);
> +	kvm_vcpu_on_spin(vcpu, kvm_arch_vcpu_in_kernel(vcpu));
>  	return 0;
>  }
>  

IIUC, diag is a privileged instruction so this an also be "true".

Paolo

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#1706116

On Tue, 8 Aug 2017 09:34:14 +0200
Paolo Bonzini <pbonzini@redhat.com> wrote:

> On 08/08/2017 06:05, Longpeng(Mike) wrote:
> >  	return 1;
> > diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
> > index ce865bd..4ea8c38 100644
> > --- a/arch/s390/kvm/diag.c
> > +++ b/arch/s390/kvm/diag.c
> > @@ -150,7 +150,7 @@ static int __diag_time_slice_end(struct kvm_vcpu *vcpu)
> >  {
> >  	VCPU_EVENT(vcpu, 5, "%s", "diag time slice end");
> >  	vcpu->stat.diagnose_44++;
> > -	kvm_vcpu_on_spin(vcpu);
> > +	kvm_vcpu_on_spin(vcpu, kvm_arch_vcpu_in_kernel(vcpu));
> >  	return 0;
> >  }
> >    
> 
> IIUC, diag is a privileged instruction so this an also be "true".
> 
> Paolo

Yes, indeed.

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#1706176

On 08.08.2017 10:42, David Hildenbrand wrote:
> 
>> +bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
>> +{
>> +	return false;
>> +}
> 
> why don't we need an EXPORT_SYMBOL here?
> 
>> +
>>  /* Just ensure a guest exit from a particular CPU */
>>  static void exit_vm_noop(void *info)
>>  {
>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>> index 15252d7..e7720d2 100644
>> --- a/virt/kvm/kvm_main.c
>> +++ b/virt/kvm/kvm_main.c
>> @@ -2317,7 +2317,7 @@ static bool kvm_vcpu_eligible_for_directed_yield(struct kvm_vcpu *vcpu)
>>  #endif
>>  }
>>  
>> -void kvm_vcpu_on_spin(struct kvm_vcpu *me)
>> +void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool me_in_kern)
>>  {
>>  	struct kvm *kvm = me->kvm;
>>  	struct kvm_vcpu *vcpu;
>> @@ -2348,6 +2348,8 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
>>  				continue;
>>  			if (swait_active(&vcpu->wq) && !kvm_arch_vcpu_runnable(vcpu))
>>  				continue;
>> +			if (me_in_kern && !kvm_arch_vcpu_in_kernel(vcpu))
>> +				continue;
> 
> 
> hm, does this patch compile? (me_in_kern)

pardon me, missed the parameter, so ignore this comment. comment
regarding splitting up below still holds :)

> 
> I would even move this to an other patch.
> 
> Maybe even split into
> 
> a) introducing kvm_arch_vcpu_in_kernel() for all archs
> b) modifying kvm_vcpu_on_spin(), passing the result from
> kvm_arch_vcpu_in_kernel()
> c) filling kvm_arch_vcpu_in_kernel() with life for different archs
> (multiple patches)
> d) pimping kvm_vcpu_on_spin()
> 
>>  			if (!kvm_vcpu_eligible_for_directed_yield(vcpu))
>>  				continue;
>>  
>>
> 
> 


-- 

Thanks,

David

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#1706178

> +bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
> +{
> +	return false;
> +}

why don't we need an EXPORT_SYMBOL here?

> +
>  /* Just ensure a guest exit from a particular CPU */
>  static void exit_vm_noop(void *info)
>  {
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 15252d7..e7720d2 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2317,7 +2317,7 @@ static bool kvm_vcpu_eligible_for_directed_yield(struct kvm_vcpu *vcpu)
>  #endif
>  }
>  
> -void kvm_vcpu_on_spin(struct kvm_vcpu *me)
> +void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool me_in_kern)
>  {
>  	struct kvm *kvm = me->kvm;
>  	struct kvm_vcpu *vcpu;
> @@ -2348,6 +2348,8 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
>  				continue;
>  			if (swait_active(&vcpu->wq) && !kvm_arch_vcpu_runnable(vcpu))
>  				continue;
> +			if (me_in_kern && !kvm_arch_vcpu_in_kernel(vcpu))
> +				continue;


hm, does this patch compile? (me_in_kern)

I would even move this to an other patch.

Maybe even split into

a) introducing kvm_arch_vcpu_in_kernel() for all archs
b) modifying kvm_vcpu_on_spin(), passing the result from
kvm_arch_vcpu_in_kernel()
c) filling kvm_arch_vcpu_in_kernel() with life for different archs
(multiple patches)
d) pimping kvm_vcpu_on_spin()

>  			if (!kvm_vcpu_eligible_for_directed_yield(vcpu))
>  				continue;
>  
> 


-- 

Thanks,

David

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#1706235

On 08/08/2017 10:42, David Hildenbrand wrote:
> 
>> +bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
>> +{
>> +	return false;
>> +}
> 
> why don't we need an EXPORT_SYMBOL here?

Is it used outside the KVM module?  I think no architecture actually needs
to export it.

>> -void kvm_vcpu_on_spin(struct kvm_vcpu *me)
>> +void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool me_in_kern)
>>  {
>>  	struct kvm *kvm = me->kvm;
>>  	struct kvm_vcpu *vcpu;
>> @@ -2348,6 +2348,8 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
>>  				continue;
>>  			if (swait_active(&vcpu->wq) && !kvm_arch_vcpu_runnable(vcpu))
>>  				continue;
>> +			if (me_in_kern && !kvm_arch_vcpu_in_kernel(vcpu))
>> +				continue;
> 
> 
> hm, does this patch compile? (me_in_kern)

Why not? :)  This is what I have:

From d62a40d49f44ff7e789a15416316ef1cba93fa85 Mon Sep 17 00:00:00 2001
From: "Longpeng(Mike)" <longpeng2@huawei.com>
Date: Tue, 8 Aug 2017 12:05:32 +0800
Subject: [PATCH 1/4] KVM: add spinlock optimization framework

If a vcpu exits due to request a user mode spinlock, then
the spinlock-holder may be preempted in user mode or kernel mode.
(Note that not all architectures trap spin loops in user mode,
only AMD x86 and ARM/ARM64 currently do).

But if a vcpu exits in kernel mode, then the holder must be
preempted in kernel mode, so we should choose a vcpu in kernel mode
as a more likely candidate for the lock holder.

This introduces kvm_arch_vcpu_in_kernel() to decide whether the
vcpu is in kernel-mode when it's preempted.  kvm_vcpu_on_spin's
new argument says the same of the spinning VCPU.

Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/arm/kvm/handle_exit.c   | 2 +-
 arch/arm64/kvm/handle_exit.c | 2 +-
 arch/mips/kvm/mips.c         | 5 +++++
 arch/powerpc/kvm/powerpc.c   | 5 +++++
 arch/s390/kvm/diag.c         | 2 +-
 arch/s390/kvm/kvm-s390.c     | 5 +++++
 arch/x86/kvm/hyperv.c        | 2 +-
 arch/x86/kvm/svm.c           | 2 +-
 arch/x86/kvm/vmx.c           | 2 +-
 arch/x86/kvm/x86.c           | 5 +++++
 include/linux/kvm_host.h     | 3 ++-
 virt/kvm/arm/arm.c           | 5 +++++
 virt/kvm/kvm_main.c          | 4 +++-
 13 files changed, 36 insertions(+), 8 deletions(-)

diff --git a/arch/arm/kvm/handle_exit.c b/arch/arm/kvm/handle_exit.c
index 54442e375354..196122bb6968 100644
--- a/arch/arm/kvm/handle_exit.c
+++ b/arch/arm/kvm/handle_exit.c
@@ -67,7 +67,7 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
 	if (kvm_vcpu_get_hsr(vcpu) & HSR_WFI_IS_WFE) {
 		trace_kvm_wfx(*vcpu_pc(vcpu), true);
 		vcpu->stat.wfe_exit_stat++;
-		kvm_vcpu_on_spin(vcpu);
+		kvm_vcpu_on_spin(vcpu, false);
 	} else {
 		trace_kvm_wfx(*vcpu_pc(vcpu), false);
 		vcpu->stat.wfi_exit_stat++;
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 17d8a1677a0b..da57622cacca 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -84,7 +84,7 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
 	if (kvm_vcpu_get_hsr(vcpu) & ESR_ELx_WFx_ISS_WFE) {
 		trace_kvm_wfx_arm64(*vcpu_pc(vcpu), true);
 		vcpu->stat.wfe_exit_stat++;
-		kvm_vcpu_on_spin(vcpu);
+		kvm_vcpu_on_spin(vcpu, false);
 	} else {
 		trace_kvm_wfx_arm64(*vcpu_pc(vcpu), false);
 		vcpu->stat.wfi_exit_stat++;
diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index d4b2ad18eef2..70208bed5a15 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -98,6 +98,11 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
 	return !!(vcpu->arch.pending_exceptions);
 }
 
+bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
+{
+	return false;
+}
+
 int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
 {
 	return 1;
 }
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 1a75c0b5f4ca..6184c45015f3 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -58,6 +58,11 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *v)
 	return !!(v->arch.pending_exceptions) || kvm_request_pending(v);
 }
 
+bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
+{
+	return false;
+}
+
 int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
 {
 	return 1;
diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
index ce865bd4f81d..6182edebea3d 100644
--- a/arch/s390/kvm/diag.c
+++ b/arch/s390/kvm/diag.c
@@ -150,7 +150,7 @@ static int __diag_time_slice_end(struct kvm_vcpu *vcpu)
 {
 	VCPU_EVENT(vcpu, 5, "%s", "diag time slice end");
 	vcpu->stat.diagnose_44++;
-	kvm_vcpu_on_spin(vcpu);
+	kvm_vcpu_on_spin(vcpu, false);
 	return 0;
 }
 
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index af09d3437631..0b0c689f1d9a 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2447,6 +2447,11 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
 	return kvm_s390_vcpu_has_irq(vcpu, 0);
 }
 
+bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
+{
+	return false;
+}
+
 void kvm_s390_vcpu_block(struct kvm_vcpu *vcpu)
 {
 	atomic_or(PROG_BLOCK_SIE, &vcpu->arch.sie_block->prog20);
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index bf9992300efa..5243d54f73ab 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1274,7 +1274,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 
 	switch (code) {
 	case HVCALL_NOTIFY_LONG_SPIN_WAIT:
-		kvm_vcpu_on_spin(vcpu);
+		kvm_vcpu_on_spin(vcpu, false);
 		break;
 	case HVCALL_POST_MESSAGE:
 	case HVCALL_SIGNAL_EVENT:
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 2432bb952a30..0cc486fd9871 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -3749,7 +3749,7 @@ static int interrupt_window_interception(struct vcpu_svm *svm)
 
 static int pause_interception(struct vcpu_svm *svm)
 {
-	kvm_vcpu_on_spin(&(svm->vcpu));
+	kvm_vcpu_on_spin(&svm->vcpu, false);
 	return 1;
 }
 
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 2c0f5287fb78..fef784c22190 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6781,7 +6781,7 @@ static int handle_pause(struct kvm_vcpu *vcpu)
 	if (ple_gap)
 		grow_ple_window(vcpu);
 
-	kvm_vcpu_on_spin(vcpu);
+	kvm_vcpu_on_spin(vcpu, false);
 	return kvm_skip_emulated_instruction(vcpu);
 }
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 33fd6b6419ef..aba9d038d09e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8432,6 +8432,11 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
 	return kvm_vcpu_running(vcpu) || kvm_vcpu_has_events(vcpu);
 }
 
+bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
+{
+	return false;
+}
+
 int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
 {
 	return kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 28112d7917c1..6882538eda32 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -720,7 +720,7 @@ int kvm_vcpu_write_guest(struct kvm_vcpu *vcpu, gpa_t gpa, const void *data,
 bool kvm_vcpu_wake_up(struct kvm_vcpu *vcpu);
 void kvm_vcpu_kick(struct kvm_vcpu *vcpu);
 int kvm_vcpu_yield_to(struct kvm_vcpu *target);
-void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu);
+void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu, bool usermode_vcpu_not_eligible);
 void kvm_load_guest_fpu(struct kvm_vcpu *vcpu);
 void kvm_put_guest_fpu(struct kvm_vcpu *vcpu);
 
@@ -800,6 +800,7 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
 void kvm_arch_hardware_unsetup(void);
 void kvm_arch_check_processor_compat(void *rtn);
 int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu);
+bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu);
 int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu);
 
 #ifndef __KVM_HAVE_ARCH_VM_ALLOC
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index a39a1e161e63..862f820d06d4 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -416,6 +416,11 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *v)
 		&& !v->arch.power_off && !v->arch.pause);
 }
 
+bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
+{
+	return false;
+}
+
 /* Just ensure a guest exit from a particular CPU */
 static void exit_vm_noop(void *info)
 {
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 15252d723b54..e17c40d986f3 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2317,7 +2317,7 @@ static bool kvm_vcpu_eligible_for_directed_yield(struct kvm_vcpu *vcpu)
 #endif
 }
 
-void kvm_vcpu_on_spin(struct kvm_vcpu *me)
+void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode)
 {
 	struct kvm *kvm = me->kvm;
 	struct kvm_vcpu *vcpu;
@@ -2348,6 +2348,8 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
 				continue;
 			if (swait_active(&vcpu->wq) && !kvm_arch_vcpu_runnable(vcpu))
 				continue;
+			if (yield_to_kernel_mode && !kvm_arch_vcpu_in_kernel(vcpu))
+				continue;
 			if (!kvm_vcpu_eligible_for_directed_yield(vcpu))
 				continue;
 
-- 
1.8.3.1


From 325c00511ab67d7e46e887ecea0d8b6b91005948 Mon Sep 17 00:00:00 2001
From: "Longpeng(Mike)" <longpeng2@huawei.com>
Date: Tue, 8 Aug 2017 12:05:33 +0800
Subject: [PATCH 2/4] KVM: X86: implement the logic for spinlock optimization

get_cpl requires vcpu_load, so we must cache the result (whether the
vcpu was preempted when its cpl=0) in kvm_vcpu_arch.

Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/include/asm/kvm_host.h | 3 +++
 arch/x86/kvm/hyperv.c           | 2 +-
 arch/x86/kvm/svm.c              | 5 ++++-
 arch/x86/kvm/vmx.c              | 8 +++++++-
 arch/x86/kvm/x86.c              | 7 ++++++-
 5 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 87ac4fba6d8e..1679aabcabe5 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -688,6 +688,9 @@ struct kvm_vcpu_arch {
 
 	/* GPA available (AMD only) */
 	bool gpa_available;
+
+	/* be preempted when it's in kernel-mode(cpl=0) */
+	bool preempted_in_kernel;
 };
 
 struct kvm_lpage_info {
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 5243d54f73ab..dc97f2544b6f 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1274,7 +1274,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 
 	switch (code) {
 	case HVCALL_NOTIFY_LONG_SPIN_WAIT:
-		kvm_vcpu_on_spin(vcpu, false);
+		kvm_vcpu_on_spin(vcpu, true);
 		break;
 	case HVCALL_POST_MESSAGE:
 	case HVCALL_SIGNAL_EVENT:
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 0cc486fd9871..fc027f2e87d1 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -3749,7 +3749,10 @@ static int interrupt_window_interception(struct vcpu_svm *svm)
 
 static int pause_interception(struct vcpu_svm *svm)
 {
-	kvm_vcpu_on_spin(&svm->vcpu, false);
+	struct kvm_vcpu *vcpu = &svm->vcpu;
+	bool in_kernel = (svm_get_cpl(vcpu) == 0);
+
+	kvm_vcpu_on_spin(vcpu, in_kernel);
 	return 1;
 }
 
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index fef784c22190..46d08b389e36 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6781,7 +6781,13 @@ static int handle_pause(struct kvm_vcpu *vcpu)
 	if (ple_gap)
 		grow_ple_window(vcpu);
 
-	kvm_vcpu_on_spin(vcpu, false);
+	/*
+	 * Intel sdm vol3 ch-25.1.3 says: The "PAUSE-loop exiting"
+	 * VM-execution control is ignored if CPL > 0. OTOH, KVM
+	 * never set PAUSE_EXITING and just only uses PLE,
+	 * so the vcpu must be CPL=0 if it gets a PAUSE exit.
+	 */
+	kvm_vcpu_on_spin(vcpu, true);
 	return kvm_skip_emulated_instruction(vcpu);
 }
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index aba9d038d09e..bee9ad0ed4cd 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2873,6 +2873,10 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
 void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 {
 	int idx;
+
+	if (vcpu->preempted)
+		vcpu->arch.preempted_in_kernel = !kvm_x86_ops->get_cpl(vcpu);
+
 	/*
 	 * Disable page faults because we're in atomic context here.
 	 * kvm_write_guest_offset_cached() would call might_fault()
@@ -7985,6 +7989,7 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
 	kvm_pmu_init(vcpu);
 
 	vcpu->arch.pending_external_vector = -1;
+	vcpu->arch.preempted_in_kernel = false;
 
 	kvm_hv_vcpu_init(vcpu);
 
@@ -8434,7 +8439,7 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
 
 bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
 {
-	return false;
+	return vcpu->arch.preempted_in_kernel;
 }
 
 int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
-- 
1.8.3.1


From c83cf5cf8d972ea37b55db7e059767f5e3af55d0 Mon Sep 17 00:00:00 2001
From: "Longpeng(Mike)" <longpeng2@huawei.com>
Date: Tue, 8 Aug 2017 12:05:34 +0800
Subject: [PATCH 3/4] KVM: s390: implements the kvm_arch_vcpu_in_kernel()

This implements kvm_arch_vcpu_in_kernel() for s390.  DIAG is a privileged
operation, so it cannot be called from problem state (user mode).

Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/s390/kvm/diag.c     | 2 +-
 arch/s390/kvm/kvm-s390.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
index 6182edebea3d..5ee90020382d 100644
--- a/arch/s390/kvm/diag.c
+++ b/arch/s390/kvm/diag.c
@@ -150,7 +150,7 @@ static int __diag_time_slice_end(struct kvm_vcpu *vcpu)
 {
 	VCPU_EVENT(vcpu, 5, "%s", "diag time slice end");
 	vcpu->stat.diagnose_44++;
-	kvm_vcpu_on_spin(vcpu, false);
+	kvm_vcpu_on_spin(vcpu, true);
 	return 0;
 }
 
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 0b0c689f1d9a..e46177bde829 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2449,7 +2449,7 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
 
 bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
 {
-	return false;
+	return !(vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE);
 }
 
 void kvm_s390_vcpu_block(struct kvm_vcpu *vcpu)
-- 
1.8.3.1


From 3d7c9a55166d7f0d955774360bca72a13b4ee96c Mon Sep 17 00:00:00 2001
From: "Longpeng(Mike)" <longpeng2@huawei.com>
Date: Tue, 8 Aug 2017 12:05:35 +0800
Subject: [PATCH 4/4] KVM: arm: implements the kvm_arch_vcpu_in_kernel()

This implements the kvm_arch_vcpu_in_kernel() for ARM, and adjusts
the calls to kvm_vcpu_on_spin().

Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/arm/kvm/handle_exit.c   | 2 +-
 arch/arm64/kvm/handle_exit.c | 2 +-
 virt/kvm/arm/arm.c           | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm/kvm/handle_exit.c b/arch/arm/kvm/handle_exit.c
index 196122bb6968..cf8bf6bf87c4 100644
--- a/arch/arm/kvm/handle_exit.c
+++ b/arch/arm/kvm/handle_exit.c
@@ -67,7 +67,7 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
 	if (kvm_vcpu_get_hsr(vcpu) & HSR_WFI_IS_WFE) {
 		trace_kvm_wfx(*vcpu_pc(vcpu), true);
 		vcpu->stat.wfe_exit_stat++;
-		kvm_vcpu_on_spin(vcpu, false);
+		kvm_vcpu_on_spin(vcpu, vcpu_mode_priv(vcpu));
 	} else {
 		trace_kvm_wfx(*vcpu_pc(vcpu), false);
 		vcpu->stat.wfi_exit_stat++;
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index da57622cacca..7debb74843a0 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -84,7 +84,7 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
 	if (kvm_vcpu_get_hsr(vcpu) & ESR_ELx_WFx_ISS_WFE) {
 		trace_kvm_wfx_arm64(*vcpu_pc(vcpu), true);
 		vcpu->stat.wfe_exit_stat++;
-		kvm_vcpu_on_spin(vcpu, false);
+		kvm_vcpu_on_spin(vcpu, vcpu_mode_priv(vcpu));
 	} else {
 		trace_kvm_wfx_arm64(*vcpu_pc(vcpu), false);
 		vcpu->stat.wfi_exit_stat++;
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 862f820d06d4..b9f68e4add71 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -418,7 +418,7 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *v)
 
 bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
 {
-	return false;
+	return vcpu_mode_priv(vcpu);
 }
 
 /* Just ensure a guest exit from a particular CPU */
-- 
1.8.3.1

[toc] | [prev] | [next] | [standalone]

#1706262

On 2017/8/8 17:00, Paolo Bonzini wrote:

> On 08/08/2017 10:42, David Hildenbrand wrote:
>>
>>> +bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
>>> +{
>>> +	return false;
>>> +}
>>
>> why don't we need an EXPORT_SYMBOL here?
> 
> Is it used outside the KVM module?  I think no architecture actually needs
> to export it.
> 


Hi Paolo & David,

In my original approach, I call kvm_arch_vcpu_in_kernel() in handle_pause(),
without EXPORT_SYMBOL the compiler reports:
 ERROR: "kvm_arch_vcpu_in_kernel" [arch/x86/kvm/kvm-intel.ko] undefined!
 ERROR: "kvm_arch_vcpu_in_kernel" [arch/x86/kvm/kvm-amd.ko] undefined!

But Paolo's approach is significantly better, it's a work of art, thanks a lot.

-- 
Regards,
Longpeng(Mike)

>>> -void kvm_vcpu_on_spin(struct kvm_vcpu *me)
>>> +void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool me_in_kern)
>>>  {
>>>  	struct kvm *kvm = me->kvm;
>>>  	struct kvm_vcpu *vcpu;
>>> @@ -2348,6 +2348,8 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
>>>  				continue;
>>>  			if (swait_active(&vcpu->wq) && !kvm_arch_vcpu_runnable(vcpu))
>>>  				continue;
>>> +			if (me_in_kern && !kvm_arch_vcpu_in_kernel(vcpu))
>>> +				continue;
>>
>>
>> hm, does this patch compile? (me_in_kern)
> 
> Why not? :)  This is what I have:
> 
>>From d62a40d49f44ff7e789a15416316ef1cba93fa85 Mon Sep 17 00:00:00 2001
> From: "Longpeng(Mike)" <longpeng2@huawei.com>
> Date: Tue, 8 Aug 2017 12:05:32 +0800
> Subject: [PATCH 1/4] KVM: add spinlock optimization framework
> 
> If a vcpu exits due to request a user mode spinlock, then
> the spinlock-holder may be preempted in user mode or kernel mode.
> (Note that not all architectures trap spin loops in user mode,
> only AMD x86 and ARM/ARM64 currently do).
> 
> But if a vcpu exits in kernel mode, then the holder must be
> preempted in kernel mode, so we should choose a vcpu in kernel mode
> as a more likely candidate for the lock holder.
> 
> This introduces kvm_arch_vcpu_in_kernel() to decide whether the
> vcpu is in kernel-mode when it's preempted.  kvm_vcpu_on_spin's
> new argument says the same of the spinning VCPU.
> 
> Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  arch/arm/kvm/handle_exit.c   | 2 +-
>  arch/arm64/kvm/handle_exit.c | 2 +-
>  arch/mips/kvm/mips.c         | 5 +++++
>  arch/powerpc/kvm/powerpc.c   | 5 +++++
>  arch/s390/kvm/diag.c         | 2 +-
>  arch/s390/kvm/kvm-s390.c     | 5 +++++
>  arch/x86/kvm/hyperv.c        | 2 +-
>  arch/x86/kvm/svm.c           | 2 +-
>  arch/x86/kvm/vmx.c           | 2 +-
>  arch/x86/kvm/x86.c           | 5 +++++
>  include/linux/kvm_host.h     | 3 ++-
>  virt/kvm/arm/arm.c           | 5 +++++
>  virt/kvm/kvm_main.c          | 4 +++-
>  13 files changed, 36 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm/kvm/handle_exit.c b/arch/arm/kvm/handle_exit.c
> index 54442e375354..196122bb6968 100644
> --- a/arch/arm/kvm/handle_exit.c
> +++ b/arch/arm/kvm/handle_exit.c
> @@ -67,7 +67,7 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
>  	if (kvm_vcpu_get_hsr(vcpu) & HSR_WFI_IS_WFE) {
>  		trace_kvm_wfx(*vcpu_pc(vcpu), true);
>  		vcpu->stat.wfe_exit_stat++;
> -		kvm_vcpu_on_spin(vcpu);
> +		kvm_vcpu_on_spin(vcpu, false);
>  	} else {
>  		trace_kvm_wfx(*vcpu_pc(vcpu), false);
>  		vcpu->stat.wfi_exit_stat++;
> diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
> index 17d8a1677a0b..da57622cacca 100644
> --- a/arch/arm64/kvm/handle_exit.c
> +++ b/arch/arm64/kvm/handle_exit.c
> @@ -84,7 +84,7 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
>  	if (kvm_vcpu_get_hsr(vcpu) & ESR_ELx_WFx_ISS_WFE) {
>  		trace_kvm_wfx_arm64(*vcpu_pc(vcpu), true);
>  		vcpu->stat.wfe_exit_stat++;
> -		kvm_vcpu_on_spin(vcpu);
> +		kvm_vcpu_on_spin(vcpu, false);
>  	} else {
>  		trace_kvm_wfx_arm64(*vcpu_pc(vcpu), false);
>  		vcpu->stat.wfi_exit_stat++;
> diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
> index d4b2ad18eef2..70208bed5a15 100644
> --- a/arch/mips/kvm/mips.c
> +++ b/arch/mips/kvm/mips.c
> @@ -98,6 +98,11 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
>  	return !!(vcpu->arch.pending_exceptions);
>  }
>  
> +bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
> +{
> +	return false;
> +}
> +
>  int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
>  {
>  	return 1;
>  }
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 1a75c0b5f4ca..6184c45015f3 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -58,6 +58,11 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *v)
>  	return !!(v->arch.pending_exceptions) || kvm_request_pending(v);
>  }
>  
> +bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
> +{
> +	return false;
> +}
> +
>  int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
>  {
>  	return 1;
> diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
> index ce865bd4f81d..6182edebea3d 100644
> --- a/arch/s390/kvm/diag.c
> +++ b/arch/s390/kvm/diag.c
> @@ -150,7 +150,7 @@ static int __diag_time_slice_end(struct kvm_vcpu *vcpu)
>  {
>  	VCPU_EVENT(vcpu, 5, "%s", "diag time slice end");
>  	vcpu->stat.diagnose_44++;
> -	kvm_vcpu_on_spin(vcpu);
> +	kvm_vcpu_on_spin(vcpu, false);
>  	return 0;
>  }
>  
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index af09d3437631..0b0c689f1d9a 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -2447,6 +2447,11 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
>  	return kvm_s390_vcpu_has_irq(vcpu, 0);
>  }
>  
> +bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
> +{
> +	return false;
> +}
> +
>  void kvm_s390_vcpu_block(struct kvm_vcpu *vcpu)
>  {
>  	atomic_or(PROG_BLOCK_SIE, &vcpu->arch.sie_block->prog20);
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index bf9992300efa..5243d54f73ab 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -1274,7 +1274,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
>  
>  	switch (code) {
>  	case HVCALL_NOTIFY_LONG_SPIN_WAIT:
> -		kvm_vcpu_on_spin(vcpu);
> +		kvm_vcpu_on_spin(vcpu, false);
>  		break;
>  	case HVCALL_POST_MESSAGE:
>  	case HVCALL_SIGNAL_EVENT:
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 2432bb952a30..0cc486fd9871 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -3749,7 +3749,7 @@ static int interrupt_window_interception(struct vcpu_svm *svm)
>  
>  static int pause_interception(struct vcpu_svm *svm)
>  {
> -	kvm_vcpu_on_spin(&(svm->vcpu));
> +	kvm_vcpu_on_spin(&svm->vcpu, false);
>  	return 1;
>  }
>  
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 2c0f5287fb78..fef784c22190 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -6781,7 +6781,7 @@ static int handle_pause(struct kvm_vcpu *vcpu)
>  	if (ple_gap)
>  		grow_ple_window(vcpu);
>  
> -	kvm_vcpu_on_spin(vcpu);
> +	kvm_vcpu_on_spin(vcpu, false);
>  	return kvm_skip_emulated_instruction(vcpu);
>  }
>  
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 33fd6b6419ef..aba9d038d09e 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -8432,6 +8432,11 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
>  	return kvm_vcpu_running(vcpu) || kvm_vcpu_has_events(vcpu);
>  }
>  
> +bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
> +{
> +	return false;
> +}
> +
>  int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
>  {
>  	return kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE;
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 28112d7917c1..6882538eda32 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -720,7 +720,7 @@ int kvm_vcpu_write_guest(struct kvm_vcpu *vcpu, gpa_t gpa, const void *data,
>  bool kvm_vcpu_wake_up(struct kvm_vcpu *vcpu);
>  void kvm_vcpu_kick(struct kvm_vcpu *vcpu);
>  int kvm_vcpu_yield_to(struct kvm_vcpu *target);
> -void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu);
> +void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu, bool usermode_vcpu_not_eligible);
>  void kvm_load_guest_fpu(struct kvm_vcpu *vcpu);
>  void kvm_put_guest_fpu(struct kvm_vcpu *vcpu);
>  
> @@ -800,6 +800,7 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
>  void kvm_arch_hardware_unsetup(void);
>  void kvm_arch_check_processor_compat(void *rtn);
>  int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu);
> +bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu);
>  int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu);
>  
>  #ifndef __KVM_HAVE_ARCH_VM_ALLOC
> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> index a39a1e161e63..862f820d06d4 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -416,6 +416,11 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *v)
>  		&& !v->arch.power_off && !v->arch.pause);
>  }
>  
> +bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
> +{
> +	return false;
> +}
> +
>  /* Just ensure a guest exit from a particular CPU */
>  static void exit_vm_noop(void *info)
>  {
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 15252d723b54..e17c40d986f3 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2317,7 +2317,7 @@ static bool kvm_vcpu_eligible_for_directed_yield(struct kvm_vcpu *vcpu)
>  #endif
>  }
>  
> -void kvm_vcpu_on_spin(struct kvm_vcpu *me)
> +void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode)
>  {
>  	struct kvm *kvm = me->kvm;
>  	struct kvm_vcpu *vcpu;
> @@ -2348,6 +2348,8 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
>  				continue;
>  			if (swait_active(&vcpu->wq) && !kvm_arch_vcpu_runnable(vcpu))
>  				continue;
> +			if (yield_to_kernel_mode && !kvm_arch_vcpu_in_kernel(vcpu))
> +				continue;
>  			if (!kvm_vcpu_eligible_for_directed_yield(vcpu))
>  				continue;
>  


-- 
Regards,
Longpeng(Mike)

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