linux-kernel - Re: [PATCH v7 05/12] KVM: arm64: PMU: Add a helper to read a vCPU's PMCR

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Message-ID: <2eb9c70b-1d7d-241b-0818-9340be896519@redhat.com>
Date:   Mon, 16 Oct 2023 22:02:21 +0200
From:   Eric Auger <eauger@...hat.com>
To:     Raghavendra Rao Ananta <rananta@...gle.com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Marc Zyngier <maz@...nel.org>
Cc:     Alexandru Elisei <alexandru.elisei@....com>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Shaoqin Huang <shahuang@...hat.com>,
        Jing Zhang <jingzhangos@...gle.com>,
        Reiji Watanabe <reijiw@...gle.com>,
        Colton Lewis <coltonlewis@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v7 05/12] KVM: arm64: PMU: Add a helper to read a vCPU's
 PMCR_EL0

Raghavendra,

On 10/10/23 01:08, Raghavendra Rao Ananta wrote:
> From: Reiji Watanabe <reijiw@...gle.com>
> 
> Add a helper to read a vCPU's PMCR_EL0, and use it when KVM
> reads a vCPU's PMCR_EL0.
> 
> The PMCR_EL0 value is tracked by a sysreg file per each vCPU.
file?
> The following patches will make (only) PMCR_EL0.N track per guest.
> Having the new helper will be useful to combine the PMCR_EL0.N
> field (tracked per guest) and the other fields (tracked per vCPU)
> to provide the value of PMCR_EL0.
> 
> No functional change intended.
> 
> Signed-off-by: Reiji Watanabe <reijiw@...gle.com>
> Signed-off-by: Raghavendra Rao Ananta <rananta@...gle.com>
Besides
Reviewed-by: Eric Auger <eric.auger@...hat.com>

Eric
> ---
>  arch/arm64/kvm/arm.c      |  3 +--
>  arch/arm64/kvm/pmu-emul.c | 21 +++++++++++++++------
>  arch/arm64/kvm/sys_regs.c |  6 +++---
>  include/kvm/arm_pmu.h     |  6 ++++++
>  4 files changed, 25 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 708a53b70a7b..0af4d6bbe3d3 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -854,8 +854,7 @@ static int check_vcpu_requests(struct kvm_vcpu *vcpu)
>  		}
>  
>  		if (kvm_check_request(KVM_REQ_RELOAD_PMU, vcpu))
> -			kvm_pmu_handle_pmcr(vcpu,
> -					    __vcpu_sys_reg(vcpu, PMCR_EL0));
> +			kvm_pmu_handle_pmcr(vcpu, kvm_vcpu_read_pmcr(vcpu));
>  
>  		if (kvm_check_request(KVM_REQ_RESYNC_PMU_EL0, vcpu))
>  			kvm_vcpu_pmu_restore_guest(vcpu);
> diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
> index cc30c246c010..a161d6266a5c 100644
> --- a/arch/arm64/kvm/pmu-emul.c
> +++ b/arch/arm64/kvm/pmu-emul.c
> @@ -72,7 +72,7 @@ static bool kvm_pmc_is_64bit(struct kvm_pmc *pmc)
>  
>  static bool kvm_pmc_has_64bit_overflow(struct kvm_pmc *pmc)
>  {
> -	u64 val = __vcpu_sys_reg(kvm_pmc_to_vcpu(pmc), PMCR_EL0);
> +	u64 val = kvm_vcpu_read_pmcr(kvm_pmc_to_vcpu(pmc));
>  
>  	return (pmc->idx < ARMV8_PMU_CYCLE_IDX && (val & ARMV8_PMU_PMCR_LP)) ||
>  	       (pmc->idx == ARMV8_PMU_CYCLE_IDX && (val & ARMV8_PMU_PMCR_LC));
> @@ -250,7 +250,7 @@ void kvm_pmu_vcpu_destroy(struct kvm_vcpu *vcpu)
>  
>  u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu)
>  {
> -	u64 val = __vcpu_sys_reg(vcpu, PMCR_EL0) >> ARMV8_PMU_PMCR_N_SHIFT;
> +	u64 val = kvm_vcpu_read_pmcr(vcpu) >> ARMV8_PMU_PMCR_N_SHIFT;
>  
>  	val &= ARMV8_PMU_PMCR_N_MASK;
>  	if (val == 0)
> @@ -272,7 +272,7 @@ void kvm_pmu_enable_counter_mask(struct kvm_vcpu *vcpu, u64 val)
>  	if (!kvm_vcpu_has_pmu(vcpu))
>  		return;
>  
> -	if (!(__vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_E) || !val)
> +	if (!(kvm_vcpu_read_pmcr(vcpu) & ARMV8_PMU_PMCR_E) || !val)
>  		return;
>  
>  	for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++) {
> @@ -324,7 +324,7 @@ static u64 kvm_pmu_overflow_status(struct kvm_vcpu *vcpu)
>  {
>  	u64 reg = 0;
>  
> -	if ((__vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_E)) {
> +	if ((kvm_vcpu_read_pmcr(vcpu) & ARMV8_PMU_PMCR_E)) {
>  		reg = __vcpu_sys_reg(vcpu, PMOVSSET_EL0);
>  		reg &= __vcpu_sys_reg(vcpu, PMCNTENSET_EL0);
>  		reg &= __vcpu_sys_reg(vcpu, PMINTENSET_EL1);
> @@ -426,7 +426,7 @@ static void kvm_pmu_counter_increment(struct kvm_vcpu *vcpu,
>  {
>  	int i;
>  
> -	if (!(__vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_E))
> +	if (!(kvm_vcpu_read_pmcr(vcpu) & ARMV8_PMU_PMCR_E))
>  		return;
>  
>  	/* Weed out disabled counters */
> @@ -569,7 +569,7 @@ void kvm_pmu_handle_pmcr(struct kvm_vcpu *vcpu, u64 val)
>  static bool kvm_pmu_counter_is_enabled(struct kvm_pmc *pmc)
>  {
>  	struct kvm_vcpu *vcpu = kvm_pmc_to_vcpu(pmc);
> -	return (__vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_E) &&
> +	return (kvm_vcpu_read_pmcr(vcpu) & ARMV8_PMU_PMCR_E) &&
>  	       (__vcpu_sys_reg(vcpu, PMCNTENSET_EL0) & BIT(pmc->idx));
>  }
>  
> @@ -1084,3 +1084,12 @@ u8 kvm_arm_pmu_get_pmuver_limit(void)
>  					      ID_AA64DFR0_EL1_PMUVer_V3P5);
>  	return FIELD_GET(ARM64_FEATURE_MASK(ID_AA64DFR0_EL1_PMUVer), tmp);
>  }
> +
> +/**
> + * kvm_vcpu_read_pmcr - Read PMCR_EL0 register for the vCPU
> + * @vcpu: The vcpu pointer
> + */
> +u64 kvm_vcpu_read_pmcr(struct kvm_vcpu *vcpu)
> +{
> +	return __vcpu_sys_reg(vcpu, PMCR_EL0);
> +}
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 08af7824e9d8..ff0f7095eaca 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -803,7 +803,7 @@ static bool access_pmcr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
>  		 * Only update writeable bits of PMCR (continuing into
>  		 * kvm_pmu_handle_pmcr() as well)
>  		 */
> -		val = __vcpu_sys_reg(vcpu, PMCR_EL0);
> +		val = kvm_vcpu_read_pmcr(vcpu);
>  		val &= ~ARMV8_PMU_PMCR_MASK;
>  		val |= p->regval & ARMV8_PMU_PMCR_MASK;
>  		if (!kvm_supports_32bit_el0())
> @@ -811,7 +811,7 @@ static bool access_pmcr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
>  		kvm_pmu_handle_pmcr(vcpu, val);
>  	} else {
>  		/* PMCR.P & PMCR.C are RAZ */
> -		val = __vcpu_sys_reg(vcpu, PMCR_EL0)
> +		val = kvm_vcpu_read_pmcr(vcpu)
>  		      & ~(ARMV8_PMU_PMCR_P | ARMV8_PMU_PMCR_C);
>  		p->regval = val;
>  	}
> @@ -860,7 +860,7 @@ static bool pmu_counter_idx_valid(struct kvm_vcpu *vcpu, u64 idx)
>  {
>  	u64 pmcr, val;
>  
> -	pmcr = __vcpu_sys_reg(vcpu, PMCR_EL0);
> +	pmcr = kvm_vcpu_read_pmcr(vcpu);
>  	val = (pmcr >> ARMV8_PMU_PMCR_N_SHIFT) & ARMV8_PMU_PMCR_N_MASK;
>  	if (idx >= val && idx != ARMV8_PMU_CYCLE_IDX) {
>  		kvm_inject_undefined(vcpu);
> diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
> index 858ed9ce828a..cd980d78b86b 100644
> --- a/include/kvm/arm_pmu.h
> +++ b/include/kvm/arm_pmu.h
> @@ -103,6 +103,7 @@ void kvm_vcpu_pmu_resync_el0(void);
>  u8 kvm_arm_pmu_get_pmuver_limit(void);
>  int kvm_arm_set_default_pmu(struct kvm *kvm);
>  
> +u64 kvm_vcpu_read_pmcr(struct kvm_vcpu *vcpu);
>  #else
>  struct kvm_pmu {
>  };
> @@ -180,6 +181,11 @@ static inline int kvm_arm_set_default_pmu(struct kvm *kvm)
>  	return -ENODEV;
>  }
>  
> +static inline u64 kvm_vcpu_read_pmcr(struct kvm_vcpu *vcpu)
> +{
> +	return 0;
> +}
> +
>  #endif
>  
>  #endif