Re: [PATCH v13 4/8] arm64: arm_pmu: Add !VHE support for exclude_host/exclude_guest attributes

[Suzuki K Poulose <suzuki.poulose@arm.com>]

On 04/09/2019 08:22 PM, 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 events based
> on their event attributes.
> 
> With !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. When
> using !exclude_hv 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>
> Acked-by: Will Deacon <will.deacon@arm.com>
> ---



>   arch/arm64/kernel/perf_event.c | 43 ++++++++++++++++++++++++++++------
>   1 file changed, 36 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
> index cccf4fc86d67..6bb28aaf5aea 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>
> @@ -528,11 +529,21 @@ 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));
> +
> +	kvm_set_pmu_events(counter_bits, attr);
> +
> +	/* We rely on the hypervisor switch code to enable guest counters */
> +	if (!kvm_pmu_counter_deferred(attr)) {
> +		armv8pmu_enable_counter(idx);
> +		if (armv8pmu_event_is_chained(event))
> +			armv8pmu_enable_counter(idx - 1);
> +	}
>   }
>   
>   static inline int armv8pmu_disable_counter(int idx)
> @@ -545,11 +556,21 @@ 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);
> +
> +	/* We rely on the hypervisor switch code to disable guest counters */
> +	if (!kvm_pmu_counter_deferred(attr)) {
> +		if (armv8pmu_event_is_chained(event))
> +			armv8pmu_disable_counter(idx - 1);
> +		armv8pmu_disable_counter(idx);
> +	}
>   }
>   
>   static inline int armv8pmu_enable_intens(int idx)
> @@ -829,11 +850,16 @@ static int armv8pmu_set_event_filter(struct hw_perf_event *event,
>   		if (!attr->exclude_kernel)
>   			config_base |= ARMV8_PMU_INCLUDE_EL2;
>   	} else {
> -		if (attr->exclude_kernel)
> -			config_base |= ARMV8_PMU_EXCLUDE_EL1;
> -		if (!attr->exclude_hv)
> +		if (!attr->exclude_hv && !attr->exclude_host)
>   			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;
>   
> @@ -863,6 +889,9 @@ 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().
> 


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