Date:   Thu, 2 Feb 2023 18:03:45 +0100
From:   Andrew Jones <ajones@ventanamicro.com>
To:     Atish Patra <atishp@rivosinc.com>
Cc:     linux-kernel@vger.kernel.org, Albert Ou <aou@eecs.berkeley.edu>,
        Anup Patel <anup@brainfault.org>,
        Atish Patra <atishp@atishpatra.org>,
        Eric Lin <eric.lin@sifive.com>, Guo Ren <guoren@kernel.org>,
        Heiko Stuebner <heiko@sntech.de>,
        kvm-riscv@lists.infradead.org, kvm@vger.kernel.org,
        linux-riscv@lists.infradead.org,
        Mark Rutland <mark.rutland@arm.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Will Deacon <will@kernel.org>
Subject: Re: [PATCH v4 07/14] RISC-V: KVM: Add skeleton support for perf
Message-ID: <20230202170345.uwi72dauzunlzxex@orel>
References: <20230201231250.3806412-1-atishp@rivosinc.com>
 <20230201231250.3806412-8-atishp@rivosinc.com>
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In-Reply-To: <20230201231250.3806412-8-atishp@rivosinc.com>
Precedence: bulk

On Wed, Feb 01, 2023 at 03:12:43PM -0800, Atish Patra wrote:
> This patch only adds barebone structure of perf implementation. Most of
> the function returns zero at this point and will be implemented
> fully in the future.
> 
> Signed-off-by: Atish Patra <atishp@rivosinc.com>
> ---
>  arch/riscv/include/asm/kvm_host.h     |   4 +
>  arch/riscv/include/asm/kvm_vcpu_pmu.h |  78 +++++++++++++++
>  arch/riscv/kvm/Makefile               |   1 +
>  arch/riscv/kvm/vcpu.c                 |   7 ++
>  arch/riscv/kvm/vcpu_pmu.c             | 136 ++++++++++++++++++++++++++
>  5 files changed, 226 insertions(+)
>  create mode 100644 arch/riscv/include/asm/kvm_vcpu_pmu.h
>  create mode 100644 arch/riscv/kvm/vcpu_pmu.c
> 
> diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
> index 93f43a3..b90be9a 100644
> --- a/arch/riscv/include/asm/kvm_host.h
> +++ b/arch/riscv/include/asm/kvm_host.h
> @@ -18,6 +18,7 @@
>  #include <asm/kvm_vcpu_insn.h>
>  #include <asm/kvm_vcpu_sbi.h>
>  #include <asm/kvm_vcpu_timer.h>
> +#include <asm/kvm_vcpu_pmu.h>
>  
>  #define KVM_MAX_VCPUS			1024
>  
> @@ -228,6 +229,9 @@ struct kvm_vcpu_arch {
>  
>  	/* Don't run the VCPU (blocked) */
>  	bool pause;
> +
> +	/* Performance monitoring context */
> +	struct kvm_pmu pmu_context;
>  };
>  
>  static inline void kvm_arch_hardware_unsetup(void) {}
> diff --git a/arch/riscv/include/asm/kvm_vcpu_pmu.h b/arch/riscv/include/asm/kvm_vcpu_pmu.h
> new file mode 100644
> index 0000000..e2b4038
> --- /dev/null
> +++ b/arch/riscv/include/asm/kvm_vcpu_pmu.h
> @@ -0,0 +1,78 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (c) 2023 Rivos Inc
> + *
> + * Authors:
> + *     Atish Patra <atishp@rivosinc.com>
> + */
> +
> +#ifndef __KVM_VCPU_RISCV_PMU_H
> +#define __KVM_VCPU_RISCV_PMU_H
> +
> +#include <linux/perf/riscv_pmu.h>
> +#include <asm/kvm_vcpu_sbi.h>
> +#include <asm/sbi.h>
> +
> +#ifdef CONFIG_RISCV_PMU_SBI
> +#define RISCV_KVM_MAX_FW_CTRS	32
> +
> +#if RISCV_KVM_MAX_FW_CTRS > 32
> +#error "Maximum firmware counter can't exceed 32 without increasing the RISCV_MAX_COUNTERS"

"The number of firmware counters cannot exceed 32 without increasing RISCV_MAX_COUNTERS"

> +#endif
> +
> +#define RISCV_MAX_COUNTERS      64

But instead of that message, what I think we need is something like

 #define RISCV_KVM_MAX_HW_CTRS	32
 #define RISCV_KVM_MAX_FW_CTRS	32
 #define RISCV_MAX_COUNTERS	(RISCV_KVM_MAX_HW_CTRS + RISCV_KVM_MAX_FW_CTRS)

 static_assert(RISCV_MAX_COUNTERS <= 64)

And then in pmu_sbi_device_probe() should ensure

  num_counters <= RISCV_MAX_COUNTERS

and pmu_sbi_get_ctrinfo() should ensure

  num_hw_ctr <= RISCV_KVM_MAX_HW_CTRS
  num_fw_ctr <= RISCV_KVM_MAX_FW_CTRS

which has to be done at runtime.

> +
> +/* Per virtual pmu counter data */
> +struct kvm_pmc {
> +	u8 idx;
> +	struct perf_event *perf_event;
> +	uint64_t counter_val;
> +	union sbi_pmu_ctr_info cinfo;
> +	/* Event monitoring status */
> +	bool started;
> +};
> +
> +/* PMU data structure per vcpu */
> +struct kvm_pmu {
> +	struct kvm_pmc pmc[RISCV_MAX_COUNTERS];
> +	/* Number of the virtual firmware counters available */
> +	int num_fw_ctrs;
> +	/* Number of the virtual hardware counters available */
> +	int num_hw_ctrs;
> +	/* A flag to indicate that pmu initialization is done */
> +	bool init_done;
> +	/* Bit map of all the virtual counter used */
> +	DECLARE_BITMAP(pmc_in_use, RISCV_MAX_COUNTERS);
> +};
> +
> +#define vcpu_to_pmu(vcpu) (&(vcpu)->arch.pmu_context)
> +#define pmu_to_vcpu(pmu)  (container_of((pmu), struct kvm_vcpu, arch.pmu_context))
> +
> +int kvm_riscv_vcpu_pmu_num_ctrs(struct kvm_vcpu *vcpu, struct kvm_vcpu_sbi_return *retdata);
> +int kvm_riscv_vcpu_pmu_ctr_info(struct kvm_vcpu *vcpu, unsigned long cidx,
> +				struct kvm_vcpu_sbi_return *retdata);
> +int kvm_riscv_vcpu_pmu_ctr_start(struct kvm_vcpu *vcpu, unsigned long ctr_base,
> +				 unsigned long ctr_mask, unsigned long flag, uint64_t ival,
> +				 struct kvm_vcpu_sbi_return *retdata);
> +int kvm_riscv_vcpu_pmu_ctr_stop(struct kvm_vcpu *vcpu, unsigned long ctr_base,
> +				unsigned long ctr_mask, unsigned long flag,
> +				struct kvm_vcpu_sbi_return *retdata);
> +int kvm_riscv_vcpu_pmu_ctr_cfg_match(struct kvm_vcpu *vcpu, unsigned long ctr_base,
> +				     unsigned long ctr_mask, unsigned long flag,
> +				     unsigned long eidx, uint64_t evtdata,
> +				     struct kvm_vcpu_sbi_return *retdata);

s/flag/flags/ for all the above prototypes and all the implementations
below.

> +int kvm_riscv_vcpu_pmu_ctr_read(struct kvm_vcpu *vcpu, unsigned long cidx,
> +				struct kvm_vcpu_sbi_return *retdata);
> +void kvm_riscv_vcpu_pmu_init(struct kvm_vcpu *vcpu);
> +void kvm_riscv_vcpu_pmu_deinit(struct kvm_vcpu *vcpu);
> +void kvm_riscv_vcpu_pmu_reset(struct kvm_vcpu *vcpu);
> +
> +#else
> +struct kvm_pmu {
> +};
> +
> +static inline void kvm_riscv_vcpu_pmu_init(struct kvm_vcpu *vcpu) {}
> +static inline void kvm_riscv_vcpu_pmu_deinit(struct kvm_vcpu *vcpu) {}
> +static inline void kvm_riscv_vcpu_pmu_reset(struct kvm_vcpu *vcpu) {}
> +#endif /* CONFIG_RISCV_PMU_SBI */
> +#endif /* !__KVM_VCPU_RISCV_PMU_H */
> diff --git a/arch/riscv/kvm/Makefile b/arch/riscv/kvm/Makefile
> index 019df920..5de1053 100644
> --- a/arch/riscv/kvm/Makefile
> +++ b/arch/riscv/kvm/Makefile
> @@ -25,3 +25,4 @@ kvm-y += vcpu_sbi_base.o
>  kvm-y += vcpu_sbi_replace.o
>  kvm-y += vcpu_sbi_hsm.o
>  kvm-y += vcpu_timer.o
> +kvm-$(CONFIG_RISCV_PMU_SBI) += vcpu_pmu.o
> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> index 7c08567..7d010b0 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -138,6 +138,8 @@ static void kvm_riscv_reset_vcpu(struct kvm_vcpu *vcpu)
>  	WRITE_ONCE(vcpu->arch.irqs_pending, 0);
>  	WRITE_ONCE(vcpu->arch.irqs_pending_mask, 0);
>  
> +	kvm_riscv_vcpu_pmu_reset(vcpu);
> +
>  	vcpu->arch.hfence_head = 0;
>  	vcpu->arch.hfence_tail = 0;
>  	memset(vcpu->arch.hfence_queue, 0, sizeof(vcpu->arch.hfence_queue));
> @@ -194,6 +196,9 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
>  	/* Setup VCPU timer */
>  	kvm_riscv_vcpu_timer_init(vcpu);
>  
> +	/* setup performance monitoring */
> +	kvm_riscv_vcpu_pmu_init(vcpu);
> +
>  	/* Reset VCPU */
>  	kvm_riscv_reset_vcpu(vcpu);
>  
> @@ -216,6 +221,8 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
>  	/* Cleanup VCPU timer */
>  	kvm_riscv_vcpu_timer_deinit(vcpu);
>  
> +	kvm_riscv_vcpu_pmu_deinit(vcpu);
> +
>  	/* Free unused pages pre-allocated for G-stage page table mappings */
>  	kvm_mmu_free_memory_cache(&vcpu->arch.mmu_page_cache);
>  }
> diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c
> new file mode 100644
> index 0000000..2dad37f
> --- /dev/null
> +++ b/arch/riscv/kvm/vcpu_pmu.c
> @@ -0,0 +1,136 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2023 Rivos Inc
> + *
> + * Authors:
> + *     Atish Patra <atishp@rivosinc.com>
> + */
> +
> +#include <linux/errno.h>
> +#include <linux/err.h>
> +#include <linux/kvm_host.h>
> +#include <linux/perf/riscv_pmu.h>
> +#include <asm/csr.h>
> +#include <asm/kvm_vcpu_sbi.h>
> +#include <asm/kvm_vcpu_pmu.h>
> +#include <linux/kvm_host.h>
> +
> +#define kvm_pmu_num_counters(pmu) ((pmu)->num_hw_ctrs + (pmu)->num_fw_ctrs)
> +
> +int kvm_riscv_vcpu_pmu_num_ctrs(struct kvm_vcpu *vcpu, struct kvm_vcpu_sbi_return *retdata)
> +{
> +	struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
> +
> +	retdata->out_val = kvm_pmu_num_counters(kvpmu);
> +
> +	return 0;
> +}
> +
> +int kvm_riscv_vcpu_pmu_ctr_info(struct kvm_vcpu *vcpu, unsigned long cidx,
> +				struct kvm_vcpu_sbi_return *retdata)
> +{
> +	struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
> +
> +	if (cidx > RISCV_MAX_COUNTERS || cidx == 1) {
> +		retdata->err_val = SBI_ERR_INVALID_PARAM;
> +		return 0;
> +	}
> +
> +	retdata->out_val = kvpmu->pmc[cidx].cinfo.value;
> +
> +	return 0;
> +}
> +
> +int kvm_riscv_vcpu_pmu_ctr_start(struct kvm_vcpu *vcpu, unsigned long ctr_base,
> +				 unsigned long ctr_mask, unsigned long flag, uint64_t ival,
> +				 struct kvm_vcpu_sbi_return *retdata)
> +{
> +	/* TODO */
> +	return 0;
> +}
> +
> +int kvm_riscv_vcpu_pmu_ctr_stop(struct kvm_vcpu *vcpu, unsigned long ctr_base,
> +				unsigned long ctr_mask, unsigned long flag,
> +				struct kvm_vcpu_sbi_return *retdata)
> +{
> +	/* TODO */
> +	return 0;
> +}
> +
> +int kvm_riscv_vcpu_pmu_ctr_cfg_match(struct kvm_vcpu *vcpu, unsigned long ctr_base,
> +				     unsigned long ctr_mask, unsigned long flag,
> +				     unsigned long eidx, uint64_t evtdata,
> +				     struct kvm_vcpu_sbi_return *retdata)
> +{
> +	/* TODO */
> +	return 0;
> +}
> +
> +int kvm_riscv_vcpu_pmu_ctr_read(struct kvm_vcpu *vcpu, unsigned long cidx,
> +				struct kvm_vcpu_sbi_return *retdata)
> +{
> +	/* TODO */
> +	return 0;
> +}
> +
> +void kvm_riscv_vcpu_pmu_init(struct kvm_vcpu *vcpu)
> +{
> +	int i = 0, ret, num_hw_ctrs = 0, hpm_width = 0;
> +	struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
> +	struct kvm_pmc *pmc;
> +
> +	ret = riscv_pmu_get_hpm_info(&hpm_width, &num_hw_ctrs);
> +	if (ret < 0 || !hpm_width || !num_hw_ctrs)
> +		return;
> +
> +	/*
> +	 * It is guranteed that RISCV_KVM_MAX_FW_CTRS can't exceed 32 as
> +	 * that may exceed total number of counters more than RISCV_MAX_COUNTERS
> +	 */
> +	kvpmu->num_hw_ctrs = num_hw_ctrs;
> +	kvpmu->num_fw_ctrs = RISCV_KVM_MAX_FW_CTRS;

If we sanity check that num_hw_ctrs <= 32 and num_fw_ctrs <= 32 at sbi_pmu
probe time, then we can also return num_fw_ctrs (or num_ctrs) along with
num_hw_ctrs from riscv_pmu_get_hpm_info(). Then, we can put the exact
number here into kvmpmu->num_fw_ctrs, rather than using its max.

> +
> +	/*
> +	 * There is no correlation between the logical hardware counter and virtual counters.
> +	 * However, we need to encode a hpmcounter CSR in the counter info field so that
> +	 * KVM can trap n emulate the read. This works well in the migration use case as
> +	 * KVM doesn't care if the actual hpmcounter is available in the hardware or not.
> +	 */
> +	for (i = 0; i < kvm_pmu_num_counters(kvpmu); i++) {
> +		/* TIME CSR shouldn't be read from perf interface */
> +		if (i == 1)
> +			continue;
> +		pmc = &kvpmu->pmc[i];
> +		pmc->idx = i;
> +		if (i < kvpmu->num_hw_ctrs) {
> +			pmc->cinfo.type = SBI_PMU_CTR_TYPE_HW;
> +			if (i < 3)
> +				/* CY, IR counters */
> +				pmc->cinfo.width = 63;
> +			else
> +				pmc->cinfo.width = hpm_width;
> +			/*
> +			 * The CSR number doesn't have any relation with the logical
> +			 * hardware counters. The CSR numbers are encoded sequentially
> +			 * to avoid maintaining a map between the virtual counter
> +			 * and CSR number.
> +			 */
> +			pmc->cinfo.csr = CSR_CYCLE + i;
> +		} else {
> +			pmc->cinfo.type = SBI_PMU_CTR_TYPE_FW;
> +			pmc->cinfo.width = BITS_PER_LONG - 1;
> +		}
> +	}
> +
> +	kvpmu->init_done = true;
> +}
> +
> +void kvm_riscv_vcpu_pmu_deinit(struct kvm_vcpu *vcpu)
> +{
> +	/* TODO */
> +}
> +
> +void kvm_riscv_vcpu_pmu_reset(struct kvm_vcpu *vcpu)
> +{
> +	kvm_riscv_vcpu_pmu_deinit(vcpu);
> +}
> -- 
> 2.25.1
>

Thanks,
drew