linux-kernel - Re: [PATCH V4 08/14] perf/x86/intel: Support per thread RDPMC TopDown metrics

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20190930155244.GP4553@hirez.programming.kicks-ass.net>
Date:   Mon, 30 Sep 2019 17:52:44 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     kan.liang@...ux.intel.com
Cc:     acme@...nel.org, mingo@...hat.com, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, jolsa@...nel.org, eranian@...gle.com,
        alexander.shishkin@...ux.intel.com, ak@...ux.intel.com
Subject: Re: [PATCH V4 08/14] perf/x86/intel: Support per thread RDPMC
 TopDown metrics

On Mon, Sep 16, 2019 at 06:41:22AM -0700, kan.liang@...ux.intel.com wrote:
> diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
> index 71f3086a8adc..7ec0f350d2ac 100644
> --- a/arch/x86/events/intel/core.c
> +++ b/arch/x86/events/intel/core.c
> @@ -2262,6 +2262,11 @@ static int icl_set_topdown_event_period(struct perf_event *event)
>  		local64_set(&hwc->period_left, 0);
>  	}
>  
> +	if ((hwc->saved_slots) && is_first_topdown_event_in_group(event)) {
> +		wrmsrl(MSR_CORE_PERF_FIXED_CTR3, hwc->saved_slots);
> +		wrmsrl(MSR_PERF_METRICS, hwc->saved_metric);
> +	}

> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index 61448c19a132..c125068f2e16 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -133,6 +133,9 @@ struct hw_perf_event {
>  
>  			struct hw_perf_event_extra extra_reg;
>  			struct hw_perf_event_extra branch_reg;
> +
> +			u64		saved_slots;
> +			u64		saved_metric;
>  		};
>  		struct { /* software */
>  			struct hrtimer	hrtimer;

Normal counters save their counter value in hwc->period_left, why does
slots need a new word for that?

And since using METRIC means non-sampling, why can't we stick that
saved_metric field in one of the unused sampling fields?

ISTR asking this before...