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From: Nilay Vaish <nilayvaish@gmail.com>
Date: Tue, 30 Aug 2016 11:11:55 -0500
Message-ID: <CACbG308C-mCLxQbZ2ZmXFiC4FdV=e-k6gKMgHeyUZ9E53epu8g@mail.gmail.com>
Subject: Re: [PATCH 04/13] perf/core: Extend perf_output_sample_regs() to
 include perf_arch_regs
To: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Cc: Linux Kernel list <linux-kernel@vger.kernel.org>,
        linuxppc-dev@lists.ozlabs.org, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>, Peter Zijlstra <peterz@infradead.org>,
        Jiri Olsa <jolsa@kernel.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Stephane Eranian <eranian@gmail.com>,
        Russell King <linux@arm.linux.org.uk>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
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On 28 August 2016 at 16:00, Madhavan Srinivasan
<maddy@linux.vnet.ibm.com> wrote:
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 274288819829..e16bf4d057d1 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -5371,16 +5371,24 @@ u64 __attribute__((weak)) perf_arch_reg_value(struct perf_arch_regs *regs,
>
>  static void
>  perf_output_sample_regs(struct perf_output_handle *handle,
> -                       struct pt_regs *regs, u64 mask)
> +                               struct perf_regs *regs, u64 mask)
>  {
>         int bit;
>         DECLARE_BITMAP(_mask, 64);
> +       u64 arch_regs_mask = regs->arch_regs_mask;
>
>         bitmap_from_u64(_mask, mask);
>         for_each_set_bit(bit, _mask, sizeof(mask) * BITS_PER_BYTE) {
>                 u64 val;
>
> -               val = perf_reg_value(regs, bit);
> +               val = perf_reg_value(regs->regs, bit);
> +               perf_output_put(handle, val);
> +       }
> +
> +       bitmap_from_u64(_mask, arch_regs_mask);
> +       for_each_set_bit(bit, _mask, sizeof(mask) * BITS_PER_BYTE) {
> +               u64 val;
> +               val = perf_arch_reg_value(regs->arch_regs, bit);
>                 perf_output_put(handle, val);
>         }
>  }
> @@ -5792,7 +5800,7 @@ void perf_output_sample(struct perf_output_handle *handle,
>                 if (abi) {
>                         u64 mask = event->attr.sample_regs_user;
>                         perf_output_sample_regs(handle,
> -                                               data->regs_user.regs,
> +                                               &data->regs_user,
>                                                 mask);
>                 }
>         }
> @@ -5827,7 +5835,7 @@ void perf_output_sample(struct perf_output_handle *handle,
>                         u64 mask = event->attr.sample_regs_intr;
>
>                         perf_output_sample_regs(handle,
> -                                               data->regs_intr.regs,
> +                                               &data->regs_intr,
>                                                 mask);
>                 }
>         }
> --
> 2.7.4
>

I would like to suggest a slightly different version.  Would it make
more sense to have something like following:

@@ -5792,7 +5800,7 @@ void perf_output_sample(struct perf_output_handle *handle,
                 if (abi) {
                        u64 mask = event->attr.sample_regs_user;
                        perf_output_sample_regs(handle,
                                                data->regs_user.regs,
                                                mask);
                }
+
+              if (arch_regs_mask) {
+                   perf_output_pmu_regs(handle,
data->regs_users.arch_regs, arch_regs_mask);
+              }
        }


Somehow I don't like outputting the two sets of registers through the
same function call.

--
Nilay