Re: [PATCH v7 13/19] KVM: ARM64: Add access handler for PMSWINC register

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

On 15/12/15 08:49, Shannon Zhao wrote:
> From: Shannon Zhao <shannon.zhao@linaro.org>
> 
> Add access handler which emulates writing and reading PMSWINC
> register and add support for creating software increment event.
> 
> Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
> ---
>  arch/arm64/kvm/sys_regs.c | 14 +++++++++++++-
>  include/kvm/arm_pmu.h     |  2 ++
>  virt/kvm/arm/pmu.c        | 32 ++++++++++++++++++++++++++++++++
>  3 files changed, 47 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index d1926c4..f09e500 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -690,6 +690,17 @@ static bool access_pmovsset(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
>  	return true;
>  }
>  
> +static bool access_pmswinc(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
> +			   const struct sys_reg_desc *r)
> +{
> +	if (p->is_write) {
> +		kvm_pmu_software_increment(vcpu, p->regval);

Shouldn't you filter this with valid counter mask?

> +		return true;
> +	} else {
> +		return read_zero(vcpu, p);

Mark just mentioned to me that reading from this register is UNDEFINED.
Which means you should generate an exception into the guest by calling
kvm_inject_undefined() for that vcpu.

> +	}
> +}
> +
>  /* 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 */						\
> @@ -900,7 +911,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  	  access_pmovsset, NULL, PMOVSSET_EL0 },
>  	/* PMSWINC_EL0 */
>  	{ Op0(0b11), Op1(0b011), CRn(0b1001), CRm(0b1100), Op2(0b100),
> -	  trap_raz_wi },
> +	  access_pmswinc, reset_unknown, PMSWINC_EL0 },
>  	/* PMSELR_EL0 */
>  	{ Op0(0b11), Op1(0b011), CRn(0b1001), CRm(0b1100), Op2(0b101),
>  	  access_pmselr, reset_unknown, PMSELR_EL0 },
> @@ -1239,6 +1250,7 @@ static const struct sys_reg_desc cp15_regs[] = {
>  	{ 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), access_pmovsset },
> +	{ Op1( 0), CRn( 9), CRm(12), Op2( 4), access_pmswinc },
>  	{ Op1( 0), CRn( 9), CRm(12), Op2( 5), access_pmselr },
>  	{ Op1( 0), CRn( 9), CRm(12), Op2( 6), access_pmceid },
>  	{ Op1( 0), CRn( 9), CRm(12), Op2( 7), access_pmceid },
> diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
> index 93aea6a..f5888eb 100644
> --- a/include/kvm/arm_pmu.h
> +++ b/include/kvm/arm_pmu.h
> @@ -39,6 +39,7 @@ 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_overflow_set(struct kvm_vcpu *vcpu, u64 val);
> +void kvm_pmu_software_increment(struct kvm_vcpu *vcpu, u64 val);
>  void kvm_pmu_set_counter_event_type(struct kvm_vcpu *vcpu, u64 data,
>  				    u64 select_idx);
>  #else
> @@ -52,6 +53,7 @@ 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_overflow_set(struct kvm_vcpu *vcpu, u64 val) {}
> +void kvm_pmu_software_increment(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 861471d..01af727 100644
> --- a/virt/kvm/arm/pmu.c
> +++ b/virt/kvm/arm/pmu.c
> @@ -150,6 +150,34 @@ void kvm_pmu_overflow_set(struct kvm_vcpu *vcpu, u64 val)
>  }
>  
>  /**
> + * kvm_pmu_software_increment - do software increment
> + * @vcpu: The vcpu pointer
> + * @val: the value guest writes to PMSWINC register
> + */
> +void kvm_pmu_software_increment(struct kvm_vcpu *vcpu, u64 val)
> +{
> +	int i;
> +	u64 type, enable, reg;
> +
> +	if (val == 0)
> +		return;
> +
> +	for (i = 0; i < ARMV8_CYCLE_IDX; i++) {
> +		if (!((val >> i) & 0x1))

Same comment as for the other patches.

> +			continue;
> +		type = vcpu_sys_reg(vcpu, PMEVTYPER0_EL0 + i)
> +		       & ARMV8_EVTYPE_EVENT;
> +		enable = vcpu_sys_reg(vcpu, PMCNTENSET_EL0);
> +		if ((type == 0) && ((enable >> i) & 0x1)) {
> +			vcpu_sys_reg(vcpu, PMEVCNTR0_EL0 + i)++;
> +			reg = vcpu_sys_reg(vcpu, PMEVCNTR0_EL0 + i);
> +			if ((reg & 0xFFFFFFFF) == 0)
> +				kvm_pmu_overflow_set(vcpu, BIT(i));

The increment handling is not very nice, as you end-up with stuff in the
upper 32bit... How about:

	reg = vcpu_sys_reg(vcpu, PMEVCNTR0_EL0 + i) + 1;
	reg = lower_32bit(reg);
	vcpu_sys_reg(vcpu, PMEVCNTR0_EL0 + i) = reg;
	if (!reg)
		kvm_pmu_overflow_set(vcpu, BIT(i));

> +		}
> +	}
> +}
> +
> +/**
>   * 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
> @@ -171,6 +199,10 @@ void kvm_pmu_set_counter_event_type(struct kvm_vcpu *vcpu, u64 data,
>  	kvm_pmu_stop_counter(vcpu, pmc);
>  	eventsel = data & ARMV8_EVTYPE_EVENT;
>  
> +	/* For software increment event it does't need to create perf event */
> +	if (eventsel == 0)
> +		return;
> +
>  	memset(&attr, 0, sizeof(struct perf_event_attr));
>  	attr.type = PERF_TYPE_RAW;
>  	attr.size = sizeof(attr);
> 

Thanks,

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