linux-kernel - Re: [PATCH V3 13/23] perf/x86/intel/lbr: Factor out intel_pmu_store

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Date:   Fri, 3 Jul 2020 21:50:24 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     kan.liang@...ux.intel.com
Cc:     mingo@...hat.com, acme@...nel.org, tglx@...utronix.de,
        bp@...en8.de, x86@...nel.org, linux-kernel@...r.kernel.org,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        jolsa@...hat.com, namhyung@...nel.org, dave.hansen@...el.com,
        yu-cheng.yu@...el.com, bigeasy@...utronix.de, gorcunov@...il.com,
        hpa@...or.com, alexey.budankov@...ux.intel.com, eranian@...gle.com,
        ak@...ux.intel.com, like.xu@...ux.intel.com,
        yao.jin@...ux.intel.com, wei.w.wang@...el.com
Subject: Re: [PATCH V3 13/23] perf/x86/intel/lbr: Factor out
 intel_pmu_store_lbr

On Fri, Jul 03, 2020 at 05:49:19AM -0700, kan.liang@...ux.intel.com wrote:
> +static void intel_pmu_store_lbr(struct cpu_hw_events *cpuc,
> +				struct lbr_entry *entries)
> +{
> +	struct perf_branch_entry *e;
> +	struct lbr_entry *lbr;
> +	u64 from, to, info;
> +	int i;
> +
> +	for (i = 0; i < x86_pmu.lbr_nr; i++) {
> +		lbr = entries ? &entries[i] : NULL;
> +		e = &cpuc->lbr_entries[i];
> +
> +		from = rdlbr_from(i, lbr);
> +		/*
> +		 * Read LBR entries until invalid entry (0s) is detected.
> +		 */
> +		if (!from)
> +			break;
> +
> +		to = rdlbr_to(i, lbr);
> +		info = rdlbr_info(i, lbr);
> +
> +		e->from		= from;
> +		e->to		= to;
> +		e->mispred	= !!(info & LBR_INFO_MISPRED);
> +		e->predicted	= !(info & LBR_INFO_MISPRED);
> +		e->in_tx	= !!(info & LBR_INFO_IN_TX);
> +		e->abort	= !!(info & LBR_INFO_ABORT);
> +		e->cycles	= info & LBR_INFO_CYCLES;
> +		e->type		= 0;
> +		e->reserved	= 0;
> +	}
> +
> +	cpuc->lbr_stack.nr = i;
> +}

If I'm not mistaken, this correctly deals with LBR_FORMAT_INFO, so can't
we also use the intel_pmu_arch_lbr_read() function for that case?

Then we can delete that section from read_64...

Index: linux-2.6/arch/x86/events/intel/core.c
===================================================================
--- linux-2.6.orig/arch/x86/events/intel/core.c
+++ linux-2.6/arch/x86/events/intel/core.c
@@ -4664,6 +4664,9 @@ __init int intel_pmu_init(void)
 		x86_pmu.lbr_read = intel_pmu_lbr_read_32;
 	}
 
+	if (x86_pmu.intel_cap.lbr_format == LBR_FORMAT_INFO)
+		x86_pmu.lbr_read = intel_pmu_arch_lbr_read;
+
 	if (boot_cpu_has(X86_FEATURE_ARCH_LBR))
 		intel_pmu_arch_lbr_init();