[PATCH v3 4/5] KVM: arm64: Mask out filtered events in PCMEID{0,1}_EL1

[Auger Eric]

Hi Marc,

On 9/8/20 9:58 AM, Marc Zyngier wrote:
> As we can now hide events from the guest, let's also adjust its view of
> PCMEID{0,1}_EL1 so that it can figure out why some common events are not
> counting as they should.
Referring to my previous comment should we filter the cycle counter out?
> 
> The astute user can still look into the TRM for their CPU and find out
> they've been cheated, though. Nobody's perfect.
> 
> Signed-off-by: Marc Zyngier <maz at kernel.org>
> ---
>  arch/arm64/kvm/pmu-emul.c | 29 +++++++++++++++++++++++++++++
>  arch/arm64/kvm/sys_regs.c |  5 +----
>  include/kvm/arm_pmu.h     |  5 +++++
>  3 files changed, 35 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
> index 67a731bafbc9..0458860bade2 100644
> --- a/arch/arm64/kvm/pmu-emul.c
> +++ b/arch/arm64/kvm/pmu-emul.c
> @@ -765,6 +765,35 @@ static int kvm_pmu_probe_pmuver(void)
>  	return pmuver;
>  }
>  
> +u64 kvm_pmu_get_pmceid(struct kvm_vcpu *vcpu, bool pmceid1)
> +{
> +	unsigned long *bmap = vcpu->kvm->arch.pmu_filter;
> +	u64 val, mask = 0;
> +	int base, i;
> +
> +	if (!pmceid1) {
> +		val = read_sysreg(pmceid0_el0);
> +		base = 0;
> +	} else {
> +		val = read_sysreg(pmceid1_el0);
> +		base = 32;
> +	}
> +
> +	if (!bmap)
> +		return val;
> +
> +	for (i = 0; i < 32; i += 8) {
s/32/4?

Thanks

Eric
> +		u64 byte;
> +
> +		byte = bitmap_get_value8(bmap, base + i);
> +		mask |= byte << i;
> +		byte = bitmap_get_value8(bmap, 0x4000 + base + i);
> +		mask |= byte << (32 + i);
> +	}
> +
> +	return val & mask;
> +}
> +
>  bool kvm_arm_support_pmu_v3(void)
>  {
>  	/*
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 077293b5115f..20ab2a7d37ca 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -769,10 +769,7 @@ static bool access_pmceid(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
>  	if (pmu_access_el0_disabled(vcpu))
>  		return false;
>  
> -	if (!(p->Op2 & 1))
> -		pmceid = read_sysreg(pmceid0_el0);
> -	else
> -		pmceid = read_sysreg(pmceid1_el0);
> +	pmceid = kvm_pmu_get_pmceid(vcpu, (p->Op2 & 1));
>  
>  	p->regval = pmceid;
>  
> diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
> index 6db030439e29..98cbfe885a53 100644
> --- a/include/kvm/arm_pmu.h
> +++ b/include/kvm/arm_pmu.h
> @@ -34,6 +34,7 @@ struct kvm_pmu {
>  u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx);
>  void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu, u64 select_idx, u64 val);
>  u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu);
> +u64 kvm_pmu_get_pmceid(struct kvm_vcpu *vcpu, bool pmceid1);
>  void kvm_pmu_vcpu_init(struct kvm_vcpu *vcpu);
>  void kvm_pmu_vcpu_reset(struct kvm_vcpu *vcpu);
>  void kvm_pmu_vcpu_destroy(struct kvm_vcpu *vcpu);
> @@ -108,6 +109,10 @@ static inline int kvm_arm_pmu_v3_enable(struct kvm_vcpu *vcpu)
>  {
>  	return 0;
>  }
> +static inline u64 kvm_pmu_get_pmceid(struct kvm_vcpu *vcpu, bool pmceid1)
> +{
> +	return 0;
> +}
>  #endif
>  
>  #endif
>