linux-kernel - Re: [PATCH v8 9/9] perf/amd/iommu: Enable support for multiple IOMMUs

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Date:   Wed, 25 Jan 2017 10:46:53 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
Cc:     linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        joro@...tes.org, bp@...en8.de, mingo@...hat.com
Subject: Re: [PATCH v8 9/9] perf/amd/iommu: Enable support for multiple IOMMUs

On Mon, Jan 16, 2017 at 01:23:36AM -0600, Suravee Suthikulpanit wrote:

> +	pi = container_of(event->pmu, struct perf_amd_iommu, pmu);
> +	hwc->idx              = pi->idx;
> +	hwc->config           = event->attr.config;
> +	hwc->extra_reg.config = event->attr.config1;

>  static void perf_iommu_enable_event(struct perf_event *ev)
>  {
> +	struct hw_perf_event *hwc = &ev->hw;
>  	u8 csource = _GET_CSOURCE(ev);
>  	u16 devid = _GET_DEVID(ev);
>  	u8 bank = _GET_BANK(ev);
> @@ -253,30 +248,34 @@ static void perf_iommu_enable_event(struct perf_event *ev)
>  	u64 reg = 0ULL;
>  
>  	reg = csource;
> -	amd_iommu_pc_set_reg(0, bank, cntr,
> +	amd_iommu_pc_set_reg(hwc->idx, bank, cntr,
>  			     IOMMU_PC_COUNTER_SRC_REG, &reg);

Please explain about this IOMMU crud, this looks like fail.

hwc->idx should be the counter, not a random pmu index.

But instead it looks like you get the counter form:

  #define _GET_CNTR(ev)       ((u8)(ev->hw.extra_reg.reg))

Which is absolutely insane.