Re: [PATCH v7 10/19] KVM: ARM64: Add access handler for PMCNTENSET and PMCNTENCLR register

[Marc Zyngier <marc.zyngier@arm.com>]

On 15/12/15 08:49, Shannon Zhao wrote:
> From: Shannon Zhao <shannon.zhao@linaro.org>
> 
> Since the reset value of PMCNTENSET and PMCNTENCLR is UNKNOWN, use
> reset_unknown for its reset handler. Add a handler to emulate writing
> PMCNTENSET or PMCNTENCLR register.
> 
> When writing to PMCNTENSET, call perf_event_enable to enable the perf
> event. When writing to PMCNTENCLR, call perf_event_disable to disable
> the perf event.
> 
> Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
> ---
>  arch/arm64/kvm/sys_regs.c | 41 +++++++++++++++++++++++++++++++----
>  include/kvm/arm_pmu.h     |  4 ++++
>  virt/kvm/arm/pmu.c        | 55 +++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 96 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index dc6bb26..f216da7 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -615,6 +615,39 @@ static bool access_pmu_evcntr(struct kvm_vcpu *vcpu,
>  	return true;
>  }
>  
> +static inline u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu)
> +{
> +	u64 val = vcpu_sys_reg(vcpu, PMCR_EL0) >> ARMV8_PMCR_N_SHIFT;
> +
> +	val &= ARMV8_PMCR_N_MASK;
> +	return GENMASK(val - 1, 0) | BIT(ARMV8_CYCLE_IDX);
> +}
> +
> +static bool access_pmcntenset(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
> +			      const struct sys_reg_desc *r)
> +{
> +	u64 val, mask;
> +
> +	mask = kvm_pmu_valid_counter_mask(vcpu);
> +	if (p->is_write) {
> +		val = p->regval & mask;
> +		if (r->Op2 & 0x1) {
> +			/* accessing PMCNTENSET_EL0 */
> +			vcpu_sys_reg(vcpu, r->reg) |= val;
> +			kvm_pmu_enable_counter(vcpu, val);
> +		} else {
> +			/* accessing PMCNTENCLR_EL0 */
> +			vcpu_sys_reg(vcpu, r->reg) &= mask;
> +			vcpu_sys_reg(vcpu, r->reg) &= ~val;
> +			kvm_pmu_disable_counter(vcpu, val);
> +		}
> +	} else {
> +		p->regval = vcpu_sys_reg(vcpu, r->reg) & mask;
> +	}
> +
> +	return true;
> +}
> +
>  /* Silly macro to expand the DBG{BCR,BVR,WVR,WCR}n_EL1 registers in one go */
>  #define DBG_BCR_BVR_WCR_WVR_EL1(n)					\
>  	/* DBGBVRn_EL1 */						\
> @@ -816,10 +849,10 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  	  access_pmcr, reset_pmcr, PMCR_EL0, },
>  	/* PMCNTENSET_EL0 */
>  	{ Op0(0b11), Op1(0b011), CRn(0b1001), CRm(0b1100), Op2(0b001),
> -	  trap_raz_wi },
> +	  access_pmcntenset, reset_unknown, PMCNTENSET_EL0 },
>  	/* PMCNTENCLR_EL0 */
>  	{ Op0(0b11), Op1(0b011), CRn(0b1001), CRm(0b1100), Op2(0b010),
> -	  trap_raz_wi },
> +	  access_pmcntenset, NULL, PMCNTENSET_EL0 },
>  	/* PMOVSCLR_EL0 */
>  	{ Op0(0b11), Op1(0b011), CRn(0b1001), CRm(0b1100), Op2(0b011),
>  	  trap_raz_wi },
> @@ -1161,8 +1194,8 @@ static const struct sys_reg_desc cp15_regs[] = {
>  
>  	/* PMU */
>  	{ Op1( 0), CRn( 9), CRm(12), Op2( 0), access_pmcr },
> -	{ Op1( 0), CRn( 9), CRm(12), Op2( 1), trap_raz_wi },
> -	{ Op1( 0), CRn( 9), CRm(12), Op2( 2), trap_raz_wi },
> +	{ Op1( 0), CRn( 9), CRm(12), Op2( 1), access_pmcntenset },
> +	{ Op1( 0), CRn( 9), CRm(12), Op2( 2), access_pmcntenset },
>  	{ Op1( 0), CRn( 9), CRm(12), Op2( 3), trap_raz_wi },
>  	{ Op1( 0), CRn( 9), CRm(12), Op2( 5), access_pmselr },
>  	{ Op1( 0), CRn( 9), CRm(12), Op2( 6), access_pmceid },
> diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
> index 14bedb0..43c4117 100644
> --- a/include/kvm/arm_pmu.h
> +++ b/include/kvm/arm_pmu.h
> @@ -36,6 +36,8 @@ struct kvm_pmu {
>  };
>  
>  u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx);
> +void kvm_pmu_disable_counter(struct kvm_vcpu *vcpu, u64 val);
> +void kvm_pmu_enable_counter(struct kvm_vcpu *vcpu, u64 val);
>  void kvm_pmu_set_counter_event_type(struct kvm_vcpu *vcpu, u64 data,
>  				    u64 select_idx);
>  #else
> @@ -46,6 +48,8 @@ u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx)
>  {
>  	return 0;
>  }
> +void kvm_pmu_disable_counter(struct kvm_vcpu *vcpu, u64 val) {}
> +void kvm_pmu_enable_counter(struct kvm_vcpu *vcpu, u64 val) {}
>  void kvm_pmu_set_counter_event_type(struct kvm_vcpu *vcpu, u64 data,
>  				    u64 select_idx) {}
>  #endif
> diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
> index b107fb8..94bff0e 100644
> --- a/virt/kvm/arm/pmu.c
> +++ b/virt/kvm/arm/pmu.c
> @@ -75,6 +75,61 @@ static void kvm_pmu_stop_counter(struct kvm_vcpu *vcpu, struct kvm_pmc *pmc)
>  }
>  
>  /**
> + * kvm_pmu_enable_counter - enable selected PMU counter
> + * @vcpu: The vcpu pointer
> + * @val: the value guest writes to PMCNTENSET register
> + *
> + * Call perf_event_enable to start counting the perf event
> + */
> +void kvm_pmu_enable_counter(struct kvm_vcpu *vcpu, u64 val)
> +{
> +	int i;
> +	struct kvm_pmu *pmu = &vcpu->arch.pmu;
> +	struct kvm_pmc *pmc;
> +
> +	if (!(vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMCR_E) || !val)
> +		return;
> +
> +	for (i = 0; i < ARMV8_MAX_COUNTERS; i++) {
> +		if (!((val >> i) & 0x1))
> +			continue;

nit: it is slightly more readable to have "if (!(val & (1 << i)))

> +
> +		pmc = &pmu->pmc[i];
> +		if (pmc->perf_event) {
> +			perf_event_enable(pmc->perf_event);
> +			if (pmc->perf_event->state != PERF_EVENT_STATE_ACTIVE)
> +				kvm_debug("fail to enable perf event\n");
> +		}
> +	}
> +}
> +
> +/**
> + * kvm_pmu_disable_counter - disable selected PMU counter
> + * @vcpu: The vcpu pointer
> + * @val: the value guest writes to PMCNTENCLR register
> + *
> + * Call perf_event_disable to stop counting the perf event
> + */
> +void kvm_pmu_disable_counter(struct kvm_vcpu *vcpu, u64 val)
> +{
> +	int i;
> +	struct kvm_pmu *pmu = &vcpu->arch.pmu;
> +	struct kvm_pmc *pmc;
> +
> +	if (!val)
> +		return;
> +
> +	for (i = 0; i < ARMV8_MAX_COUNTERS; i++) {
> +		if (!((val >> i) & 0x1))

Same here.

> +			continue;
> +
> +		pmc = &pmu->pmc[i];
> +		if (pmc->perf_event)
> +			perf_event_disable(pmc->perf_event);
> +	}
> +}
> +
> +/**
>   * kvm_pmu_set_counter_event_type - set selected counter to monitor some event
>   * @vcpu: The vcpu pointer
>   * @data: The data guest writes to PMXEVTYPER_EL0
> 

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...