linux-kernel - Re: [PATCH -next] riscv: perf: RISCV_BASE

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Date:   Tue, 12 May 2020 14:02:00 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     wangkefeng.wang@...wei.com
CC:     Paul Walmsley <paul.walmsley@...ive.com>,
        linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
        wangkefeng.wang@...wei.com, alankao@...estech.com
Subject:     Re: [PATCH -next] riscv: perf: RISCV_BASE_PMU should be closeable

On Thu, 07 May 2020 08:04:45 PDT (-0700), wangkefeng.wang@...wei.com wrote:
> As 178e9fc47aae("perf: riscv: preliminary RISC-V support") said,
> For RISCV_BASE_PMU, 'this option can also be disable to reduce kernel size',
> but it could not work well, we need diable both RISCV_BASE_PMU and
> PERF_EVENTS manually, or build error will occur when only disable
> RISCV_BASE_PMU.

I'm worried this belies a larger issue related to how this PMU stuff works, but
we have only one PMU right now so it's not a pressing issue.  I've taken this
onto fixes.

Thanks!

>
> Cc: Alan Kao <alankao@...estech.com>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
> ---
>  arch/riscv/include/asm/perf_event.h | 8 ++------
>  arch/riscv/kernel/Makefile          | 2 +-
>  2 files changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/arch/riscv/include/asm/perf_event.h b/arch/riscv/include/asm/perf_event.h
> index 0234048b12bc..062efd3a1d5d 100644
> --- a/arch/riscv/include/asm/perf_event.h
> +++ b/arch/riscv/include/asm/perf_event.h
> @@ -12,19 +12,14 @@
>  #include <linux/ptrace.h>
>  #include <linux/interrupt.h>
>
> +#ifdef CONFIG_RISCV_BASE_PMU
>  #define RISCV_BASE_COUNTERS	2
>
>  /*
>   * The RISCV_MAX_COUNTERS parameter should be specified.
>   */
>
> -#ifdef CONFIG_RISCV_BASE_PMU
>  #define RISCV_MAX_COUNTERS	2
> -#endif
> -
> -#ifndef RISCV_MAX_COUNTERS
> -#error "Please provide a valid RISCV_MAX_COUNTERS for the PMU."
> -#endif
>
>  /*
>   * These are the indexes of bits in counteren register *minus* 1,
> @@ -82,6 +77,7 @@ struct riscv_pmu {
>  	int		irq;
>  };
>
> +#endif
>  #ifdef CONFIG_PERF_EVENTS
>  #define perf_arch_bpf_user_pt_regs(regs) (struct user_regs_struct *)regs
>  #endif
> diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
> index 1f5736e996fd..b355cf485671 100644
> --- a/arch/riscv/kernel/Makefile
> +++ b/arch/riscv/kernel/Makefile
> @@ -43,7 +43,7 @@ obj-$(CONFIG_MODULE_SECTIONS)	+= module-sections.o
>  obj-$(CONFIG_FUNCTION_TRACER)	+= mcount.o ftrace.o
>  obj-$(CONFIG_DYNAMIC_FTRACE)	+= mcount-dyn.o
>
> -obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o
> +obj-$(CONFIG_RISCV_BASE_PMU)	+= perf_event.o
>  obj-$(CONFIG_PERF_EVENTS)	+= perf_callchain.o
>  obj-$(CONFIG_HAVE_PERF_REGS)	+= perf_regs.o
>  obj-$(CONFIG_RISCV_SBI)		+= sbi.o