diff mbox series

[2/3] KVM: x86: Introduce definitions to support static calls for kvm_pmu_ops

Message ID 20211103070310.43380-3-likexu@tencent.com (mailing list archive)
State New, archived
Headers show
Series Use static_call for kvm_pmu_ops | expand

Commit Message

Like Xu Nov. 3, 2021, 7:03 a.m. UTC 
Use static calls to improve kvm_pmu_ops performance. Introduce the
definitions that will be used by a subsequent patch to actualize the
savings. Add a new kvm-x86-pmu-ops.h header that can be used for the
definition of static calls. This header is also intended to be
used to simplify the defition of amd_pmu_ops and intel_pmu_ops.

Like what we did for kvm_x86_ops, 'pmu_ops' can be covered by
static calls in a simlilar manner for insignificant but not
negligible performance impact, especially on older models.

Signed-off-by: Like Xu <likexu@tencent.com>
---
 arch/x86/include/asm/kvm-x86-pmu-ops.h | 32 ++++++++++++++++++++++++++
 arch/x86/kvm/pmu.c                     |  7 ++++++
 arch/x86/kvm/pmu.h                     | 15 ++++++++++++
 3 files changed, 54 insertions(+)
 create mode 100644 arch/x86/include/asm/kvm-x86-pmu-ops.h

Comments

Sean Christopherson Nov. 5, 2021, 3:48 p.m. UTC | #1 
On Wed, Nov 03, 2021, Like Xu wrote:
> diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
> index 0db1887137d9..b6f08c719125 100644
> --- a/arch/x86/kvm/pmu.c
> +++ b/arch/x86/kvm/pmu.c
> @@ -50,6 +50,13 @@
>  struct kvm_pmu_ops kvm_pmu_ops __read_mostly;
>  EXPORT_SYMBOL_GPL(kvm_pmu_ops);
>  
> +#define	KVM_X86_PMU_OP(func)	\
> +	DEFINE_STATIC_CALL_NULL(kvm_x86_pmu_##func,	\
> +				*(((struct kvm_pmu_ops *)0)->func))
> +#define	KVM_X86_PMU_OP_NULL	KVM_X86_PMU_OP

More of a question for the existing code, what's the point of KVM_X86_OP_NULL?
AFAICT, it always resolves to KVM_X86_OP.  Unless there's some magic I'm missing,
I vote we remove KVM_X86_OP_NULL and then not introduce KVM_X86_PMU_OP_NULL.
And I'm pretty sure it's useless, e.g. get_cs_db_l_bits is defined with the NULL
variant, but it's never NULL and its calls aren't guarded with anything.  And if
KVM_X86_OP_NULL is intended to aid in documenting behavior, it's doing a pretty
miserable job of that :-)

> +#include <asm/kvm-x86-pmu-ops.h>
> +EXPORT_STATIC_CALL_GPL(kvm_x86_pmu_is_valid_msr);

I'll double down on my nVMX suggestion so that this export can be avoided.

>  static void kvm_pmi_trigger_fn(struct irq_work *irq_work)
>  {
>  	struct kvm_pmu *pmu = container_of(irq_work, struct kvm_pmu, irq_work);
> diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
> index b2fe135d395a..e5550d4acf14 100644
> --- a/arch/x86/kvm/pmu.h
> +++ b/arch/x86/kvm/pmu.h
> @@ -3,6 +3,8 @@
>  #define __KVM_X86_PMU_H
>  
>  #include <linux/nospec.h>
> +#include <linux/static_call_types.h>
> +#include <linux/static_call.h>
>  
>  #define vcpu_to_pmu(vcpu) (&(vcpu)->arch.pmu)
>  #define pmu_to_vcpu(pmu)  (container_of((pmu), struct kvm_vcpu, arch.pmu))
> @@ -45,6 +47,19 @@ struct kvm_pmu_ops {
>  	void (*cleanup)(struct kvm_vcpu *vcpu);
>  };
>  
> +#define	KVM_X86_PMU_OP(func)	\
> +	DECLARE_STATIC_CALL(kvm_x86_pmu_##func, *(((struct kvm_pmu_ops *)0)->func))
> +#define	KVM_X86_PMU_OP_NULL	KVM_X86_PMU_OP
> +#include <asm/kvm-x86-pmu-ops.h>
> +
> +static inline void kvm_pmu_ops_static_call_update(void)
> +{
> +#define	KVM_X86_PMU_OP(func)	\
> +	static_call_update(kvm_x86_pmu_##func, kvm_pmu_ops.func)
> +#define	KVM_X86_PMU_OP_NULL	KVM_X86_PMU_OP
> +#include <asm/kvm-x86-pmu-ops.h>
> +}

As alluded to in patch 01, I'd prefer these go in kvm_ops_static_call_update()
to keep the static call magic somewhat contained.

> +
>  static inline u64 pmc_bitmask(struct kvm_pmc *pmc)
>  {
>  	struct kvm_pmu *pmu = pmc_to_pmu(pmc);
> -- 
> 2.33.0
>
Like Xu Nov. 8, 2021, 9:31 a.m. UTC | #2 
On 5/11/2021 11:48 pm, Sean Christopherson wrote:
> On Wed, Nov 03, 2021, Like Xu wrote:
>> diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
>> index 0db1887137d9..b6f08c719125 100644
>> --- a/arch/x86/kvm/pmu.c
>> +++ b/arch/x86/kvm/pmu.c
>> @@ -50,6 +50,13 @@
>>   struct kvm_pmu_ops kvm_pmu_ops __read_mostly;
>>   EXPORT_SYMBOL_GPL(kvm_pmu_ops);
>>   
>> +#define	KVM_X86_PMU_OP(func)	\
>> +	DEFINE_STATIC_CALL_NULL(kvm_x86_pmu_##func,	\
>> +				*(((struct kvm_pmu_ops *)0)->func))
>> +#define	KVM_X86_PMU_OP_NULL	KVM_X86_PMU_OP
> 
> More of a question for the existing code, what's the point of KVM_X86_OP_NULL?

The comment says:

  * KVM_X86_OP_NULL() can leave a NULL definition for the
  * case where there is no definition or a function name that
  * doesn't match the typical naming convention is supplied.

Does it help ?

> AFAICT, it always resolves to KVM_X86_OP.  Unless there's some magic I'm missing,
> I vote we remove KVM_X86_OP_NULL and then not introduce KVM_X86_PMU_OP_NULL.
> And I'm pretty sure it's useless, e.g. get_cs_db_l_bits is defined with the NULL

This transitions will not be included in the next version. Open to you.

> variant, but it's never NULL and its calls aren't guarded with anything.  And if
> KVM_X86_OP_NULL is intended to aid in documenting behavior, it's doing a pretty
> miserable job of that :-)
> 
>> +#include <asm/kvm-x86-pmu-ops.h>
>> +EXPORT_STATIC_CALL_GPL(kvm_x86_pmu_is_valid_msr);
> 
> I'll double down on my nVMX suggestion so that this export can be avoided.

Fine to me.

> 
>>   static void kvm_pmi_trigger_fn(struct irq_work *irq_work)
>>   {
>>   	struct kvm_pmu *pmu = container_of(irq_work, struct kvm_pmu, irq_work);
>> diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
>> index b2fe135d395a..e5550d4acf14 100644
>> --- a/arch/x86/kvm/pmu.h
>> +++ b/arch/x86/kvm/pmu.h
>> @@ -3,6 +3,8 @@
>>   #define __KVM_X86_PMU_H
>>   
>>   #include <linux/nospec.h>
>> +#include <linux/static_call_types.h>
>> +#include <linux/static_call.h>
>>   
>>   #define vcpu_to_pmu(vcpu) (&(vcpu)->arch.pmu)
>>   #define pmu_to_vcpu(pmu)  (container_of((pmu), struct kvm_vcpu, arch.pmu))
>> @@ -45,6 +47,19 @@ struct kvm_pmu_ops {
>>   	void (*cleanup)(struct kvm_vcpu *vcpu);
>>   };
>>   
>> +#define	KVM_X86_PMU_OP(func)	\
>> +	DECLARE_STATIC_CALL(kvm_x86_pmu_##func, *(((struct kvm_pmu_ops *)0)->func))
>> +#define	KVM_X86_PMU_OP_NULL	KVM_X86_PMU_OP
>> +#include <asm/kvm-x86-pmu-ops.h>
>> +
>> +static inline void kvm_pmu_ops_static_call_update(void)
>> +{
>> +#define	KVM_X86_PMU_OP(func)	\
>> +	static_call_update(kvm_x86_pmu_##func, kvm_pmu_ops.func)
>> +#define	KVM_X86_PMU_OP_NULL	KVM_X86_PMU_OP
>> +#include <asm/kvm-x86-pmu-ops.h>
>> +}
> 
> As alluded to in patch 01, I'd prefer these go in kvm_ops_static_call_update()
> to keep the static call magic somewhat contained.

Thank and applied.

> 
>> +
>>   static inline u64 pmc_bitmask(struct kvm_pmc *pmc)
>>   {
>>   	struct kvm_pmu *pmu = pmc_to_pmu(pmc);
>> -- 
>> 2.33.0
>>
>
Sean Christopherson Nov. 8, 2021, 3:41 p.m. UTC | #3 
On Mon, Nov 08, 2021, Like Xu wrote:
> On 5/11/2021 11:48 pm, Sean Christopherson wrote:
> > On Wed, Nov 03, 2021, Like Xu wrote:
> > > diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
> > > index 0db1887137d9..b6f08c719125 100644
> > > --- a/arch/x86/kvm/pmu.c
> > > +++ b/arch/x86/kvm/pmu.c
> > > @@ -50,6 +50,13 @@
> > >   struct kvm_pmu_ops kvm_pmu_ops __read_mostly;
> > >   EXPORT_SYMBOL_GPL(kvm_pmu_ops);
> > > +#define	KVM_X86_PMU_OP(func)	\
> > > +	DEFINE_STATIC_CALL_NULL(kvm_x86_pmu_##func,	\
> > > +				*(((struct kvm_pmu_ops *)0)->func))
> > > +#define	KVM_X86_PMU_OP_NULL	KVM_X86_PMU_OP
> > 
> > More of a question for the existing code, what's the point of KVM_X86_OP_NULL?
> 
> The comment says:
> 
>  * KVM_X86_OP_NULL() can leave a NULL definition for the
>  * case where there is no definition or a function name that
>  * doesn't match the typical naming convention is supplied.
> 
> Does it help ?

No.  I understand the original intent of KVM_X86_OP_NULL, but unless there's some
form of enforcement, it does more harm than good because it can very easily become
stale, e.g. see get_cs_db_l_bits().  I guess "what's the point of KVM_X86_OP_NULL?"
was somewhat of a rhetorical question.

> > AFAICT, it always resolves to KVM_X86_OP.  Unless there's some magic I'm missing,
> > I vote we remove KVM_X86_OP_NULL and then not introduce KVM_X86_PMU_OP_NULL.
> > And I'm pretty sure it's useless, e.g. get_cs_db_l_bits is defined with the NULL
diff mbox series

Patch

diff --git a/arch/x86/include/asm/kvm-x86-pmu-ops.h b/arch/x86/include/asm/kvm-x86-pmu-ops.h
new file mode 100644
index 000000000000..b7713b16d21d
--- /dev/null
+++ b/arch/x86/include/asm/kvm-x86-pmu-ops.h
@@ -0,0 +1,32 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#if !defined(KVM_X86_PMU_OP) || !defined(KVM_X86_PMU_OP_NULL)
+BUILD_BUG_ON(1)
+#endif
+
+/*
+ * KVM_X86_PMU_OP() and KVM_X86_PMU_OP_NULL() are used to
+ * help generate "static_call()"s. They are also intended for use when defining
+ * the amd/intel KVM_X86_PMU_OPs. KVM_X86_PMU_OP() can be used
+ * for those functions that follow the [amd|intel]_func_name convention.
+ * KVM_X86_PMU_OP_NULL() can leave a NULL definition for the
+ * case where there is no definition or a function name that
+ * doesn't match the typical naming convention is supplied.
+ */
+KVM_X86_PMU_OP(find_arch_event);
+KVM_X86_PMU_OP(find_fixed_event);
+KVM_X86_PMU_OP(pmc_is_enabled);
+KVM_X86_PMU_OP(pmc_idx_to_pmc);
+KVM_X86_PMU_OP(rdpmc_ecx_to_pmc);
+KVM_X86_PMU_OP(msr_idx_to_pmc);
+KVM_X86_PMU_OP(is_valid_rdpmc_ecx);
+KVM_X86_PMU_OP(is_valid_msr);
+KVM_X86_PMU_OP(get_msr);
+KVM_X86_PMU_OP(set_msr);
+KVM_X86_PMU_OP(refresh);
+KVM_X86_PMU_OP(init);
+KVM_X86_PMU_OP(reset);
+KVM_X86_PMU_OP_NULL(deliver_pmi);
+KVM_X86_PMU_OP_NULL(cleanup);
+
+#undef KVM_X86_PMU_OP
+#undef KVM_X86_PMU_OP_NULL
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 0db1887137d9..b6f08c719125 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -50,6 +50,13 @@ 
 struct kvm_pmu_ops kvm_pmu_ops __read_mostly;
 EXPORT_SYMBOL_GPL(kvm_pmu_ops);
 
+#define	KVM_X86_PMU_OP(func)	\
+	DEFINE_STATIC_CALL_NULL(kvm_x86_pmu_##func,	\
+				*(((struct kvm_pmu_ops *)0)->func))
+#define	KVM_X86_PMU_OP_NULL	KVM_X86_PMU_OP
+#include <asm/kvm-x86-pmu-ops.h>
+EXPORT_STATIC_CALL_GPL(kvm_x86_pmu_is_valid_msr);
+
 static void kvm_pmi_trigger_fn(struct irq_work *irq_work)
 {
 	struct kvm_pmu *pmu = container_of(irq_work, struct kvm_pmu, irq_work);
diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
index b2fe135d395a..e5550d4acf14 100644
--- a/arch/x86/kvm/pmu.h
+++ b/arch/x86/kvm/pmu.h
@@ -3,6 +3,8 @@ 
 #define __KVM_X86_PMU_H
 
 #include <linux/nospec.h>
+#include <linux/static_call_types.h>
+#include <linux/static_call.h>
 
 #define vcpu_to_pmu(vcpu) (&(vcpu)->arch.pmu)
 #define pmu_to_vcpu(pmu)  (container_of((pmu), struct kvm_vcpu, arch.pmu))
@@ -45,6 +47,19 @@  struct kvm_pmu_ops {
 	void (*cleanup)(struct kvm_vcpu *vcpu);
 };
 
+#define	KVM_X86_PMU_OP(func)	\
+	DECLARE_STATIC_CALL(kvm_x86_pmu_##func, *(((struct kvm_pmu_ops *)0)->func))
+#define	KVM_X86_PMU_OP_NULL	KVM_X86_PMU_OP
+#include <asm/kvm-x86-pmu-ops.h>
+
+static inline void kvm_pmu_ops_static_call_update(void)
+{
+#define	KVM_X86_PMU_OP(func)	\
+	static_call_update(kvm_x86_pmu_##func, kvm_pmu_ops.func)
+#define	KVM_X86_PMU_OP_NULL	KVM_X86_PMU_OP
+#include <asm/kvm-x86-pmu-ops.h>
+}
+
 static inline u64 pmc_bitmask(struct kvm_pmc *pmc)
 {
 	struct kvm_pmu *pmu = pmc_to_pmu(pmc);