[PATCH v5 0/4] arm64: Support perf event modifiers :G and :H

[PATCH v5 0/4] arm64: Support perf event modifiers :G and :H

[Andrew Murray]

This patchset provides support for perf event modifiers :G and :H which
allows for filtering of PMU events between host and guests when used
with KVM.

As the underlying hardware cannot distinguish between guest and host
context, the performance counters must be stopped and started upon
entry/exit to the guest. This is performed at EL2 in a way that
minimizes overhead and improves accuracy of recording events that only
occur in the requested context.

This has been tested with VHE and non-VHE kernels with a KVM guest.

Changes from v4:

 - Prevent unnecessary write_sysreg calls by improving
   __pmu_switch_to_xxx logic.

Changes from v3:

 - Remove confusing _only suffix from bitfields in kvm_cpu_context
 - Remove unnecessary condition when clearing event bits in disable
 - Simplify API of KVM accessors
 - Prevent unnecessary setting of pmcnten when guest/host events are
   the same.

Changes from v2:

 - Ensured that exclude_kernel works for guest
 - Removed unnecessary exclusion of EL2 with exclude_host on !VHE
 - Renamed kvm_clr_set_host_pmu_events to reflect args order
 - Added additional information to isb patch

Changes from v1:

 - Removed unnecessary exclusion of EL1 with exclude_guest on VHE
 - Removed unnecessary isb from existing perf_event.c driver
 - Folded perf_event.c patches together
 - Added additional information to last patch commit message

Andrew Murray (4):
  arm64: arm_pmu: remove unnecessary isb instruction
  arm64: KVM: add accessors to track guest/host only counters
  arm64: arm_pmu: Add support for exclude_host/exclude_guest attributes
  arm64: KVM: Enable support for :G/:H perf event modifiers

 arch/arm64/include/asm/kvm_host.h | 24 +++++++++++++++++++
 arch/arm64/kernel/perf_event.c    | 49 ++++++++++++++++++++++++++++++++-------
 arch/arm64/kvm/hyp/switch.c       | 38 ++++++++++++++++++++++++++++++
 3 files changed, 103 insertions(+), 8 deletions(-)

-- 
2.7.4


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[PATCH v5 1/4] arm64: arm_pmu: remove unnecessary isb instruction

[Andrew Murray]

The armv8pmu_enable_event_counter function issues an isb instruction
after enabling a pair of counters - this doesn't provide any value
and is inconsistent with the armv8pmu_disable_event_counter.

In any case armv8pmu_enable_event_counter is always called with the
PMU stopped. Starting the PMU with armv8pmu_start results in an isb
instruction being issued prior to writing to PMCR_EL0.

Let's remove the unnecessary isb instruction.

Signed-off-by: Andrew Murray <andrew.murray@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
---
 arch/arm64/kernel/perf_event.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
index 8e38d52..de564ae 100644
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c
@@ -652,7 +652,6 @@ static inline void armv8pmu_enable_event_counter(struct perf_event *event)
 	armv8pmu_enable_counter(idx);
 	if (armv8pmu_event_is_chained(event))
 		armv8pmu_enable_counter(idx - 1);
-	isb();
 }
 
 static inline int armv8pmu_disable_counter(int idx)
-- 
2.7.4


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[PATCH v5 2/4] arm64: KVM: add accessors to track guest/host only counters

[Andrew Murray]

In order to effeciently enable/disable guest/host only perf counters
at guest entry/exit we add bitfields to kvm_cpu_context for guest and
host events as well as accessors for updating them.

Signed-off-by: Andrew Murray <andrew.murray@arm.com>
---
 arch/arm64/include/asm/kvm_host.h | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 1550192..800c87b 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -203,6 +203,8 @@ struct kvm_cpu_context {
 	};
 
 	struct kvm_vcpu *__hyp_running_vcpu;
+	u32 events_host;
+	u32 events_guest;
 };
 
 typedef struct kvm_cpu_context kvm_cpu_context_t;
@@ -467,11 +469,33 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu);
 
+#define KVM_PMU_EVENTS_HOST	1
+#define KVM_PMU_EVENTS_GUEST	2
+
 #ifdef CONFIG_KVM /* Avoid conflicts with core headers if CONFIG_KVM=n */
 static inline int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
 {
 	return kvm_arch_vcpu_run_map_fp(vcpu);
 }
+static inline void kvm_set_pmu_events(u32 set, int flags)
+{
+	kvm_cpu_context_t *ctx = this_cpu_ptr(&kvm_host_cpu_state);
+
+	if (flags & KVM_PMU_EVENTS_HOST)
+		ctx->events_host |= set;
+	if (flags & KVM_PMU_EVENTS_GUEST)
+		ctx->events_guest |= set;
+}
+static inline void kvm_clr_pmu_events(u32 clr)
+{
+	kvm_cpu_context_t *ctx = this_cpu_ptr(&kvm_host_cpu_state);
+
+	ctx->events_host &= ~clr;
+	ctx->events_guest &= ~clr;
+}
+#else
+static inline void kvm_set_pmu_events(u32 set, int flags) {}
+static inline void kvm_clr_pmu_events(u32 clr) {}
 #endif
 
 static inline void kvm_arm_vhe_guest_enter(void)
-- 
2.7.4


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Re: [PATCH v5 2/4] arm64: KVM: add accessors to track guest/host only counters

[Suzuki K Poulose]

Hi Andrew,

On 05/12/2018 15:30, Andrew Murray wrote:
> In order to effeciently enable/disable guest/host only perf counters
> at guest entry/exit we add bitfields to kvm_cpu_context for guest and
> host events as well as accessors for updating them.
> 
> Signed-off-by: Andrew Murray <andrew.murray@arm.com>
> ---
>   arch/arm64/include/asm/kvm_host.h | 24 ++++++++++++++++++++++++
>   1 file changed, 24 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 1550192..800c87b 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -203,6 +203,8 @@ struct kvm_cpu_context {
>   	};
>   
>   	struct kvm_vcpu *__hyp_running_vcpu;
> +	u32 events_host;
> +	u32 events_guest;
>   };
>   
>   typedef struct kvm_cpu_context kvm_cpu_context_t;
> @@ -467,11 +469,33 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu);
>   void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu);
>   void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu);
>   
> +#define KVM_PMU_EVENTS_HOST	1
> +#define KVM_PMU_EVENTS_GUEST	2
> +
>   #ifdef CONFIG_KVM /* Avoid conflicts with core headers if CONFIG_KVM=n */
>   static inline int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
>   {
>   	return kvm_arch_vcpu_run_map_fp(vcpu);
>   }
> +static inline void kvm_set_pmu_events(u32 set, int flags)
> +{
> +	kvm_cpu_context_t *ctx = this_cpu_ptr(&kvm_host_cpu_state);
> +
> +	if (flags & KVM_PMU_EVENTS_HOST)
> +		ctx->events_host |= set;
> +	if (flags & KVM_PMU_EVENTS_GUEST)
> +		ctx->events_guest |= set;

You seem to be passing a single flag at a time ever, in the next patch.
Either we can batch the calls in the next patch, or make this a real number and
not a flag. g.g, enum { HOST,  GUEST } or even a bool.

I think the former sounds better.

Cheers
Suzuki

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Re: [PATCH v5 2/4] arm64: KVM: add accessors to track guest/host only counters

[Suzuki K Poulose]

On 06/12/2018 17:21, Suzuki K Poulose wrote:
> Hi Andrew,
> 
> On 05/12/2018 15:30, Andrew Murray wrote:
>> In order to effeciently enable/disable guest/host only perf counters
>> at guest entry/exit we add bitfields to kvm_cpu_context for guest and
>> host events as well as accessors for updating them.
>>
>> Signed-off-by: Andrew Murray <andrew.murray@arm.com>
>> ---
>>    arch/arm64/include/asm/kvm_host.h | 24 ++++++++++++++++++++++++
>>    1 file changed, 24 insertions(+)
>>
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index 1550192..800c87b 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -203,6 +203,8 @@ struct kvm_cpu_context {
>>    	};
>>    
>>    	struct kvm_vcpu *__hyp_running_vcpu;
>> +	u32 events_host;
>> +	u32 events_guest;
>>    };
>>    
>>    typedef struct kvm_cpu_context kvm_cpu_context_t;
>> @@ -467,11 +469,33 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu);
>>    void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu);
>>    void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu);
>>    
>> +#define KVM_PMU_EVENTS_HOST	1
>> +#define KVM_PMU_EVENTS_GUEST	2
>> +
>>    #ifdef CONFIG_KVM /* Avoid conflicts with core headers if CONFIG_KVM=n */
>>    static inline int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
>>    {
>>    	return kvm_arch_vcpu_run_map_fp(vcpu);
>>    }
>> +static inline void kvm_set_pmu_events(u32 set, int flags)
>> +{
>> +	kvm_cpu_context_t *ctx = this_cpu_ptr(&kvm_host_cpu_state);
>> +
>> +	if (flags & KVM_PMU_EVENTS_HOST)
>> +		ctx->events_host |= set;
>> +	if (flags & KVM_PMU_EVENTS_GUEST)
>> +		ctx->events_guest |= set;
> 
> You seem to be passing a single flag at a time ever, in the next patch.
> Either we can batch the calls in the next patch, or make this a real number and
> not a flag. g.g, enum { HOST,  GUEST } or even a bool.
> 
> I think the former sounds better.

Having another look at patch-3, we can never club set() calls for host & guest 
events, we should go for the latter.

Suzuki


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Re: [PATCH v5 2/4] arm64: KVM: add accessors to track guest/host only counters

[Andrew Murray]

On Thu, Dec 06, 2018 at 06:51:37PM +0000, Suzuki K Poulose wrote:
> 
> 
> On 06/12/2018 17:21, Suzuki K Poulose wrote:
> > Hi Andrew,
> > 
> > On 05/12/2018 15:30, Andrew Murray wrote:
> > > In order to effeciently enable/disable guest/host only perf counters
> > > at guest entry/exit we add bitfields to kvm_cpu_context for guest and
> > > host events as well as accessors for updating them.
> > > 
> > > Signed-off-by: Andrew Murray <andrew.murray@arm.com>
> > > ---
> > >    arch/arm64/include/asm/kvm_host.h | 24 ++++++++++++++++++++++++
> > >    1 file changed, 24 insertions(+)
> > > 
> > > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> > > index 1550192..800c87b 100644
> > > --- a/arch/arm64/include/asm/kvm_host.h
> > > +++ b/arch/arm64/include/asm/kvm_host.h
> > > @@ -203,6 +203,8 @@ struct kvm_cpu_context {
> > >    	};
> > >    	struct kvm_vcpu *__hyp_running_vcpu;
> > > +	u32 events_host;
> > > +	u32 events_guest;
> > >    };
> > >    typedef struct kvm_cpu_context kvm_cpu_context_t;
> > > @@ -467,11 +469,33 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu);
> > >    void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu);
> > >    void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu);
> > > +#define KVM_PMU_EVENTS_HOST	1
> > > +#define KVM_PMU_EVENTS_GUEST	2
> > > +
> > >    #ifdef CONFIG_KVM /* Avoid conflicts with core headers if CONFIG_KVM=n */
> > >    static inline int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
> > >    {
> > >    	return kvm_arch_vcpu_run_map_fp(vcpu);
> > >    }
> > > +static inline void kvm_set_pmu_events(u32 set, int flags)
> > > +{
> > > +	kvm_cpu_context_t *ctx = this_cpu_ptr(&kvm_host_cpu_state);
> > > +
> > > +	if (flags & KVM_PMU_EVENTS_HOST)
> > > +		ctx->events_host |= set;
> > > +	if (flags & KVM_PMU_EVENTS_GUEST)
> > > +		ctx->events_guest |= set;
> > 
> > You seem to be passing a single flag at a time ever, in the next patch.
> > Either we can batch the calls in the next patch, or make this a real number and
> > not a flag. g.g, enum { HOST,  GUEST } or even a bool.
> > 
> > I think the former sounds better.
> 
> Having another look at patch-3, we can never club set() calls for host &
> guest events, we should go for the latter.

Well we could always do this..

        u32 flags = 0;
        if (!attr->exclude_host)
                flags |= KVM_PMU_EVENTS_HOST;
        if (!attr->exclude_guest)
                flags |= KVM_PMU_EVENTS_GUEST;

        kvm_set_pmu_events(counter_bits, flags);

Thanks,

Andrew Murray

> 
> Suzuki
> 

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Re: [PATCH v5 2/4] arm64: KVM: add accessors to track guest/host only counters

[Suzuki K Poulose]

On 06/12/2018 19:21, Andrew Murray wrote:
> On Thu, Dec 06, 2018 at 06:51:37PM +0000, Suzuki K Poulose wrote:
>>
>>
>> On 06/12/2018 17:21, Suzuki K Poulose wrote:
>>> Hi Andrew,
>>>
>>> On 05/12/2018 15:30, Andrew Murray wrote:
>>>> In order to effeciently enable/disable guest/host only perf counters
>>>> at guest entry/exit we add bitfields to kvm_cpu_context for guest and
>>>> host events as well as accessors for updating them.
>>>>
>>>> Signed-off-by: Andrew Murray <andrew.murray@arm.com>
>>>> ---
>>>>     arch/arm64/include/asm/kvm_host.h | 24 ++++++++++++++++++++++++
>>>>     1 file changed, 24 insertions(+)
>>>>
>>>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>>>> index 1550192..800c87b 100644
>>>> --- a/arch/arm64/include/asm/kvm_host.h
>>>> +++ b/arch/arm64/include/asm/kvm_host.h
>>>> @@ -203,6 +203,8 @@ struct kvm_cpu_context {
>>>>     	};
>>>>     	struct kvm_vcpu *__hyp_running_vcpu;
>>>> +	u32 events_host;
>>>> +	u32 events_guest;
>>>>     };
>>>>     typedef struct kvm_cpu_context kvm_cpu_context_t;
>>>> @@ -467,11 +469,33 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu);
>>>>     void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu);
>>>>     void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu);
>>>> +#define KVM_PMU_EVENTS_HOST	1
>>>> +#define KVM_PMU_EVENTS_GUEST	2
>>>> +
>>>>     #ifdef CONFIG_KVM /* Avoid conflicts with core headers if CONFIG_KVM=n */
>>>>     static inline int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
>>>>     {
>>>>     	return kvm_arch_vcpu_run_map_fp(vcpu);
>>>>     }
>>>> +static inline void kvm_set_pmu_events(u32 set, int flags)
>>>> +{
>>>> +	kvm_cpu_context_t *ctx = this_cpu_ptr(&kvm_host_cpu_state);
>>>> +
>>>> +	if (flags & KVM_PMU_EVENTS_HOST)
>>>> +		ctx->events_host |= set;
>>>> +	if (flags & KVM_PMU_EVENTS_GUEST)
>>>> +		ctx->events_guest |= set;
>>>
>>> You seem to be passing a single flag at a time ever, in the next patch.
>>> Either we can batch the calls in the next patch, or make this a real number and
>>> not a flag. g.g, enum { HOST,  GUEST } or even a bool.
>>>
>>> I think the former sounds better.
>>
>> Having another look at patch-3, we can never club set() calls for host &
>> guest events, we should go for the latter.
> 
> Well we could always do this..
> 
>          u32 flags = 0;
>          if (!attr->exclude_host)
>                  flags |= KVM_PMU_EVENTS_HOST;
>          if (!attr->exclude_guest)
>                  flags |= KVM_PMU_EVENTS_GUEST;
> 
>          kvm_set_pmu_events(counter_bits, flags);

Yes, I think this should be fine.

Cheers
Suzuki

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[PATCH v5 3/4] arm64: arm_pmu: Add support for exclude_host/exclude_guest attributes

[Andrew Murray]

Add support for the :G and :H attributes in perf by handling the
exclude_host/exclude_guest event attributes.

We notify KVM of counters that we wish to be enabled or disabled on
guest entry/exit and thus defer from starting or stopping :G events
as per the events exclude_host attribute.

With both VHE and non-VHE we switch the counters between host/guest
at EL2. We are able to eliminate counters counting host events on
the boundaries of guest entry/exit when using :G by filtering out
EL2 for exclude_host. However when using :H unless exclude_hv is set
on non-VHE then there is a small blackout window at the guest
entry/exit where host events are not captured.

Signed-off-by: Andrew Murray <andrew.murray@arm.com>
---
 arch/arm64/kernel/perf_event.c | 48 ++++++++++++++++++++++++++++++++++++------
 1 file changed, 41 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
index de564ae..a5bd626 100644
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c
@@ -26,6 +26,7 @@
 
 #include <linux/acpi.h>
 #include <linux/clocksource.h>
+#include <linux/kvm_host.h>
 #include <linux/of.h>
 #include <linux/perf/arm_pmu.h>
 #include <linux/platform_device.h>
@@ -647,11 +648,23 @@ static inline int armv8pmu_enable_counter(int idx)
 
 static inline void armv8pmu_enable_event_counter(struct perf_event *event)
 {
+	struct perf_event_attr *attr = &event->attr;
 	int idx = event->hw.idx;
+	u32 counter_bits = BIT(ARMV8_IDX_TO_COUNTER(idx));
 
-	armv8pmu_enable_counter(idx);
 	if (armv8pmu_event_is_chained(event))
-		armv8pmu_enable_counter(idx - 1);
+		counter_bits |= BIT(ARMV8_IDX_TO_COUNTER(idx - 1));
+
+	if (!attr->exclude_host)
+		kvm_set_pmu_events(counter_bits, KVM_PMU_EVENTS_HOST);
+	if (!attr->exclude_guest)
+		kvm_set_pmu_events(counter_bits, KVM_PMU_EVENTS_GUEST);
+
+	if (!attr->exclude_host) {
+		armv8pmu_enable_counter(idx);
+		if (armv8pmu_event_is_chained(event))
+			armv8pmu_enable_counter(idx - 1);
+	}
 }
 
 static inline int armv8pmu_disable_counter(int idx)
@@ -664,11 +677,20 @@ static inline int armv8pmu_disable_counter(int idx)
 static inline void armv8pmu_disable_event_counter(struct perf_event *event)
 {
 	struct hw_perf_event *hwc = &event->hw;
+	struct perf_event_attr *attr = &event->attr;
 	int idx = hwc->idx;
+	u32 counter_bits = BIT(ARMV8_IDX_TO_COUNTER(idx));
 
 	if (armv8pmu_event_is_chained(event))
-		armv8pmu_disable_counter(idx - 1);
-	armv8pmu_disable_counter(idx);
+		counter_bits |= BIT(ARMV8_IDX_TO_COUNTER(idx - 1));
+
+	kvm_clr_pmu_events(counter_bits);
+
+	if (!attr->exclude_host) {
+		if (armv8pmu_event_is_chained(event))
+			armv8pmu_disable_counter(idx - 1);
+		armv8pmu_disable_counter(idx);
+	}
 }
 
 static inline int armv8pmu_enable_intens(int idx)
@@ -943,16 +965,25 @@ static int armv8pmu_set_event_filter(struct hw_perf_event *event,
 	 * Therefore we ignore exclude_hv in this configuration, since
 	 * there's no hypervisor to sample anyway. This is consistent
 	 * with other architectures (x86 and Power).
+	 *
+	 * To eliminate counting host events on the boundaries of
+	 * guest entry/exit we ensure EL2 is not included in hyp mode
+	 * with !exclude_host.
 	 */
 	if (is_kernel_in_hyp_mode()) {
-		if (!attr->exclude_kernel)
+		if (!attr->exclude_kernel && !attr->exclude_host)
 			config_base |= ARMV8_PMU_INCLUDE_EL2;
 	} else {
-		if (attr->exclude_kernel)
-			config_base |= ARMV8_PMU_EXCLUDE_EL1;
 		if (!attr->exclude_hv)
 			config_base |= ARMV8_PMU_INCLUDE_EL2;
 	}
+
+	/*
+	 * Filter out !VHE kernels and guest kernels
+	 */
+	if (attr->exclude_kernel)
+		config_base |= ARMV8_PMU_EXCLUDE_EL1;
+
 	if (attr->exclude_user)
 		config_base |= ARMV8_PMU_EXCLUDE_EL0;
 
@@ -976,6 +1007,9 @@ static void armv8pmu_reset(void *info)
 		armv8pmu_disable_intens(idx);
 	}
 
+	/* Clear the counters we flip at guest entry/exit */
+	kvm_clr_pmu_events(U32_MAX);
+
 	/*
 	 * Initialize & Reset PMNC. Request overflow interrupt for
 	 * 64 bit cycle counter but cheat in armv8pmu_write_counter().
-- 
2.7.4


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Re: [PATCH v5 3/4] arm64: arm_pmu: Add support for exclude_host/exclude_guest attributes

[Suzuki K Poulose]

On 05/12/2018 15:30, Andrew Murray wrote:
> Add support for the :G and :H attributes in perf by handling the
> exclude_host/exclude_guest event attributes.
> 
> We notify KVM of counters that we wish to be enabled or disabled on
> guest entry/exit and thus defer from starting or stopping :G events
> as per the events exclude_host attribute.
> 
> With both VHE and non-VHE we switch the counters between host/guest
> at EL2. We are able to eliminate counters counting host events on
> the boundaries of guest entry/exit when using :G by filtering out
> EL2 for exclude_host. However when using :H unless exclude_hv is set
> on non-VHE then there is a small blackout window at the guest
> entry/exit where host events are not captured.
> 
> Signed-off-by: Andrew Murray <andrew.murray@arm.com>
> ---

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>


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[PATCH v5 4/4] arm64: KVM: Enable support for :G/:H perf event modifiers

[Andrew Murray]

Enable/disable event counters as appropriate when entering and exiting
the guest to enable support for guest or host only event counting.

For both VHE and non-VHE we switch the counters between host/guest at
EL2. EL2 is filtered out by the PMU when we are using the :G modifier.

The PMU may be on when we change which counters are enabled however
we avoid adding an isb as we instead rely on existing context
synchronisation events: the isb in kvm_arm_vhe_guest_exit for VHE and
the eret from the hvc in kvm_call_hyp.

Signed-off-by: Andrew Murray <andrew.murray@arm.com>
---
 arch/arm64/kvm/hyp/switch.c | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index d496ef5..e505cad 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -373,6 +373,32 @@ static bool __hyp_text __hyp_switch_fpsimd(struct kvm_vcpu *vcpu)
 	return true;
 }
 
+static bool __hyp_text __pmu_switch_to_guest(struct kvm_cpu_context *host_ctxt)
+{
+	u32 clr = host_ctxt->events_host & ~host_ctxt->events_guest;
+	u32 set = host_ctxt->events_guest & ~host_ctxt->events_host;
+
+	if (clr)
+		write_sysreg(clr, pmcntenclr_el0);
+
+	if (set)
+		write_sysreg(set, pmcntenset_el0);
+
+	return (clr || set);
+}
+
+static void __hyp_text __pmu_switch_to_host(struct kvm_cpu_context *host_ctxt)
+{
+	u32 clr = host_ctxt->events_guest & ~host_ctxt->events_host;
+	u32 set = host_ctxt->events_host & ~host_ctxt->events_guest;
+
+	if (clr)
+		write_sysreg(clr, pmcntenclr_el0);
+
+	if (set)
+		write_sysreg(set, pmcntenset_el0);
+}
+
 /*
  * Return true when we were able to fixup the guest exit and should return to
  * the guest, false when we should restore the host state and return to the
@@ -488,12 +514,15 @@ int kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu)
 {
 	struct kvm_cpu_context *host_ctxt;
 	struct kvm_cpu_context *guest_ctxt;
+	bool pmu_switch_needed;
 	u64 exit_code;
 
 	host_ctxt = vcpu->arch.host_cpu_context;
 	host_ctxt->__hyp_running_vcpu = vcpu;
 	guest_ctxt = &vcpu->arch.ctxt;
 
+	pmu_switch_needed = __pmu_switch_to_guest(host_ctxt);
+
 	sysreg_save_host_state_vhe(host_ctxt);
 
 	__activate_traps(vcpu);
@@ -524,6 +553,9 @@ int kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu)
 
 	__debug_switch_to_host(vcpu);
 
+	if (pmu_switch_needed)
+		__pmu_switch_to_host(host_ctxt);
+
 	return exit_code;
 }
 
@@ -532,6 +564,7 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu)
 {
 	struct kvm_cpu_context *host_ctxt;
 	struct kvm_cpu_context *guest_ctxt;
+	bool pmu_switch_needed;
 	u64 exit_code;
 
 	vcpu = kern_hyp_va(vcpu);
@@ -540,6 +573,8 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu)
 	host_ctxt->__hyp_running_vcpu = vcpu;
 	guest_ctxt = &vcpu->arch.ctxt;
 
+	pmu_switch_needed = __pmu_switch_to_guest(host_ctxt);
+
 	__sysreg_save_state_nvhe(host_ctxt);
 
 	__activate_traps(vcpu);
@@ -586,6 +621,9 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu)
 	 */
 	__debug_switch_to_host(vcpu);
 
+	if (pmu_switch_needed)
+		__pmu_switch_to_host(host_ctxt);
+
 	return exit_code;
 }
 
-- 
2.7.4


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Re: [PATCH v5 4/4] arm64: KVM: Enable support for :G/:H perf event modifiers

[Suzuki K Poulose]

On 05/12/2018 15:30, Andrew Murray wrote:
> Enable/disable event counters as appropriate when entering and exiting
> the guest to enable support for guest or host only event counting.
> 
> For both VHE and non-VHE we switch the counters between host/guest at
> EL2. EL2 is filtered out by the PMU when we are using the :G modifier.
> 
> The PMU may be on when we change which counters are enabled however
> we avoid adding an isb as we instead rely on existing context
> synchronisation events: the isb in kvm_arm_vhe_guest_exit for VHE and
> the eret from the hvc in kvm_call_hyp.
> 
> Signed-off-by: Andrew Murray <andrew.murray@arm.com>
> ---
>   arch/arm64/kvm/hyp/switch.c | 38 ++++++++++++++++++++++++++++++++++++++
>   1 file changed, 38 insertions(+)
> 

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>

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