linux-kernel - Re: [PATCH V4 1/4] arm_pmu: acpi: Refactor arm_spe_acpi_register

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Message-ID: <20230811101201.GA6827@willie-the-truck>
Date:   Fri, 11 Aug 2023 11:12:01 +0100
From:   Will Deacon <will@...nel.org>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, suzuki.poulose@....com,
        yangyicong@...wei.com, Sami Mujawar <sami.mujawar@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Rutland <mark.rutland@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        James Clark <james.clark@....com>, coresight@...ts.linaro.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4 1/4] arm_pmu: acpi: Refactor
 arm_spe_acpi_register_device()

On Fri, Aug 11, 2023 at 02:13:42PM +0530, Anshuman Khandual wrote:
> On 8/8/23 13:52, Anshuman Khandual wrote:
> > +	/*
> > +	 * Sanity check all the GICC tables for the same interrupt
> > +	 * number. For now, only support homogeneous ACPI machines.
> > +	 */
> > +	for_each_possible_cpu(cpu) {
> > +		struct acpi_madt_generic_interrupt *gicc;
> > +
> > +		gicc = acpi_cpu_get_madt_gicc(cpu);
> > +		if (gicc->header.length < len)
> > +			return gsi ? -ENXIO : 0;
> > +
> > +		this_gsi = parse_gsi(gicc);
> > +		if (!this_gsi)
> > +			return gsi ? -ENXIO : 0;
> > +
> > +		this_hetid = find_acpi_cpu_topology_hetero_id(cpu);
> > +		if (!gsi) {
> > +			hetid = this_hetid;
> > +			gsi = this_gsi;
> > +		} else if (hetid != this_hetid || gsi != this_gsi) {
> > +			pr_warn("ACPI: %s: must be homogeneous\n", pdev->name);
> > +			return -ENXIO;
> > +		}
> > +	}
> 
> As discussed on the previous version i.e V3 thread, will move the
> 'this_gsi' check after parse_gsi(), inside if (!gsi) conditional
> block. This will treat subsequent cpu parse_gsi()'s failure as a
> mismatch thus triggering the pr_warn() message.
> 
> diff --git a/drivers/perf/arm_pmu_acpi.c b/drivers/perf/arm_pmu_acpi.c
> index 845683ca7c64..6eae772d6298 100644
> --- a/drivers/perf/arm_pmu_acpi.c
> +++ b/drivers/perf/arm_pmu_acpi.c
> @@ -98,11 +98,11 @@ arm_acpi_register_pmu_device(struct platform_device *pdev, u8 len,
>                         return gsi ? -ENXIO : 0;
>  
>                 this_gsi = parse_gsi(gicc);
> -               if (!this_gsi)
> -                       return gsi ? -ENXIO : 0;
> -
>                 this_hetid = find_acpi_cpu_topology_hetero_id(cpu);
>                 if (!gsi) {
> +                       if (!this_gsi)
> +                               return 0;

Why do you need this hunk?

Will