linux-kernel - Re: [PATCH v2 09/11] RISC-V: KVM: Implement trap & emulate for hpmcounters

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Message-ID: <20230113114740.6eophcwagnm6mw7o@orel>
Date:   Fri, 13 Jan 2023 12:47:40 +0100
From:   Andrew Jones <ajones@...tanamicro.com>
To:     Atish Patra <atishp@...osinc.com>
Cc:     linux-kernel@...r.kernel.org, Anup Patel <anup@...infault.org>,
        Atish Patra <atishp@...shpatra.org>,
        Guo Ren <guoren@...nel.org>, kvm-riscv@...ts.infradead.org,
        kvm@...r.kernel.org, linux-riscv@...ts.infradead.org,
        Mark Rutland <mark.rutland@....com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Sergey Matyukevich <sergey.matyukevich@...tacore.com>,
        Eric Lin <eric.lin@...ive.com>, Will Deacon <will@...nel.org>
Subject: Re: [PATCH v2 09/11] RISC-V: KVM: Implement trap & emulate for
 hpmcounters

On Thu, Dec 15, 2022 at 09:00:44AM -0800, Atish Patra wrote:
> As the KVM guests only see the virtual PMU counters, all hpmcounter
> access should trap and KVM emulates the read access on behalf of guests.
> 
> Signed-off-by: Atish Patra <atishp@...osinc.com>
> ---
>  arch/riscv/include/asm/kvm_vcpu_pmu.h | 16 ++++++++++
>  arch/riscv/kvm/vcpu_insn.c            |  4 ++-
>  arch/riscv/kvm/vcpu_pmu.c             | 44 ++++++++++++++++++++++++++-
>  3 files changed, 62 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/riscv/include/asm/kvm_vcpu_pmu.h b/arch/riscv/include/asm/kvm_vcpu_pmu.h
> index 6a8c0f7..7a9a8e6 100644
> --- a/arch/riscv/include/asm/kvm_vcpu_pmu.h
> +++ b/arch/riscv/include/asm/kvm_vcpu_pmu.h
> @@ -43,6 +43,19 @@ struct kvm_pmu {
>  #define vcpu_to_pmu(vcpu) (&(vcpu)->arch.pmu)
>  #define pmu_to_vcpu(pmu)  (container_of((pmu), struct kvm_vcpu, arch.pmu))
>  
> +#if defined(CONFIG_32BIT)
> +#define KVM_RISCV_VCPU_HPMCOUNTER_CSR_FUNCS \
> +{ .base = CSR_CYCLEH,      .count = 31, .func = kvm_riscv_vcpu_pmu_read_hpm }, \
> +{ .base = CSR_CYCLE,      .count = 31, .func = kvm_riscv_vcpu_pmu_read_hpm },
> +#else
> +#define KVM_RISCV_VCPU_HPMCOUNTER_CSR_FUNCS \
> +{ .base = CSR_CYCLE,      .count = 31, .func = kvm_riscv_vcpu_pmu_read_hpm },
> +#endif
> +
> +int kvm_riscv_vcpu_pmu_read_hpm(struct kvm_vcpu *vcpu, unsigned int csr_num,
> +				unsigned long *val, unsigned long new_val,
> +				unsigned long wr_mask);
> +
>  int kvm_riscv_vcpu_pmu_num_ctrs(struct kvm_vcpu *vcpu, struct kvm_vcpu_sbi_ext_data *edata);
>  int kvm_riscv_vcpu_pmu_ctr_info(struct kvm_vcpu *vcpu, unsigned long cidx,
>  				struct kvm_vcpu_sbi_ext_data *edata);
> @@ -65,6 +78,9 @@ void kvm_riscv_vcpu_pmu_reset(struct kvm_vcpu *vcpu);
>  #else
>  struct kvm_pmu {
>  };
> +#define KVM_RISCV_VCPU_HPMCOUNTER_CSR_FUNCS \
> +{ .base = 0,      .count = 0, .func = NULL },
> +
>  
>  static inline int kvm_riscv_vcpu_pmu_init(struct kvm_vcpu *vcpu)
>  {
> diff --git a/arch/riscv/kvm/vcpu_insn.c b/arch/riscv/kvm/vcpu_insn.c
> index 1ff2649..f689337 100644
> --- a/arch/riscv/kvm/vcpu_insn.c
> +++ b/arch/riscv/kvm/vcpu_insn.c
> @@ -213,7 +213,9 @@ struct csr_func {
>  		    unsigned long wr_mask);
>  };
>  
> -static const struct csr_func csr_funcs[] = {};
> +static const struct csr_func csr_funcs[] = {
> +	KVM_RISCV_VCPU_HPMCOUNTER_CSR_FUNCS
> +};
>  
>  /**
>   * kvm_riscv_vcpu_csr_return -- Handle CSR read/write after user space
> diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c
> index 0f0748f1..53c4163 100644
> --- a/arch/riscv/kvm/vcpu_pmu.c
> +++ b/arch/riscv/kvm/vcpu_pmu.c
> @@ -17,6 +17,43 @@
>  
>  #define kvm_pmu_num_counters(pmu) ((pmu)->num_hw_ctrs + (pmu)->num_fw_ctrs)
>  
> +static int pmu_ctr_read(struct kvm_vcpu *vcpu, unsigned long cidx,
> +			unsigned long *out_val)
> +{
> +	struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
> +	struct kvm_pmc *pmc;
> +	u64 enabled, running;
> +
> +	pmc = &kvpmu->pmc[cidx];
> +	if (!pmc->perf_event)
> +		return -EINVAL;
> +
> +	pmc->counter_val += perf_event_read_value(pmc->perf_event, &enabled, &running);
> +	*out_val = pmc->counter_val;
> +
> +	return 0;
> +}
> +
> +int kvm_riscv_vcpu_pmu_read_hpm(struct kvm_vcpu *vcpu, unsigned int csr_num,
> +				unsigned long *val, unsigned long new_val,
> +				unsigned long wr_mask)
> +{
> +	struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
> +	int cidx, ret = KVM_INSN_CONTINUE_NEXT_SEPC;
> +
> +	if (!kvpmu || !kvpmu->init_done)
> +		return KVM_INSN_EXIT_TO_USER_SPACE;
> +
> +	if (wr_mask)
> +		return KVM_INSN_ILLEGAL_TRAP;

nit: add blank line here

> +	cidx = csr_num - CSR_CYCLE;
> +
> +	if (pmu_ctr_read(vcpu, cidx, val) < 0)
> +		return KVM_INSN_EXIT_TO_USER_SPACE;
> +
> +	return ret;
> +}
> +
>  int kvm_riscv_vcpu_pmu_num_ctrs(struct kvm_vcpu *vcpu, struct kvm_vcpu_sbi_ext_data *edata)
>  {
>  	struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
> @@ -69,7 +106,12 @@ int kvm_riscv_vcpu_pmu_ctr_cfg_match(struct kvm_vcpu *vcpu, unsigned long ctr_ba
>  int kvm_riscv_vcpu_pmu_ctr_read(struct kvm_vcpu *vcpu, unsigned long cidx,
>  				struct kvm_vcpu_sbi_ext_data *edata)
>  {
> -	/* TODO */
> +	int ret;
> +
> +	ret = pmu_ctr_read(vcpu, cidx, &edata->out_val);
> +	if (ret == -EINVAL)
> +		edata->err_val = SBI_ERR_INVALID_PARAM;
> +
>  	return 0;
>  }
>  
> -- 
> 2.25.1
>

Otherwise

Reviewed-by: Andrew Jones <ajones@...tanamicro.com>