linux-kernel - Re: [PATCH V3 1/2] perf/x86/intel/uncore: Skip discovery table for offline dies

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Message-ID: <047a815b-2b69-4dda-9ba0-6a91f5d955ce@linux.intel.com>
Date: Fri, 16 Jan 2026 13:19:31 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: Zide Chen <zide.chen@...el.com>, Peter Zijlstra <peterz@...radead.org>,
 Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Andi Kleen <ak@...ux.intel.com>, Eranian Stephane <eranian@...gle.com>
Cc: linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
 Xudong Hao <xudong.hao@...el.com>, Falcon Thomas <thomas.falcon@...el.com>,
 Steve Wahl <steve.wahl@....com>
Subject: Re: [PATCH V3 1/2] perf/x86/intel/uncore: Skip discovery table for
 offline dies


On 1/16/2026 11:11 AM, Zide Chen wrote:
> This warning can be triggered if NUMA is disabled and the system
> boots with fewer CPUs than the number of CPUs in die 0.
>
> WARNING: CPU: 9 PID: 7257 at uncore.c:1157 uncore_pci_pmu_register+0x136/0x160 [intel_uncore]
>
> Currently, the discovery table continues to be parsed even if all CPUs
> in the associated die are offline.  This can lead to an array overflow
> at "pmu->boxes[die] = box" in uncore_pci_pmu_register(), which may
> trigger the warning above or cause other issues.
>
> Reported-by: Steve Wahl <steve.wahl@....com>
> Tested-by: Steve Wahl <steve.wahl@....com>
> Fixes: edae1f06c2cd ("perf/x86/intel/uncore: Parse uncore discovery tables")
> Signed-off-by: Zide Chen <zide.chen@...el.com>
> ---
> V2:
> - Add the Tested-by tag
> - Rebase onto perf/core (base commit: a491c02c2770)
>
> V3:
> - Remove the overly cautious WARN_ON()
>
>  arch/x86/events/intel/uncore_discovery.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/events/intel/uncore_discovery.c b/arch/x86/events/intel/uncore_discovery.c
> index b46575254dbe..0e414cecb6f2 100644
> --- a/arch/x86/events/intel/uncore_discovery.c
> +++ b/arch/x86/events/intel/uncore_discovery.c
> @@ -366,7 +366,7 @@ static bool uncore_discovery_pci(struct uncore_discovery_domain *domain)
>  				     (val & UNCORE_DISCOVERY_DVSEC2_BIR_MASK) * UNCORE_DISCOVERY_BIR_STEP;
>  
>  			die = get_device_die_id(dev);
> -			if (die < 0)
> +			if ((die < 0) || (die >= uncore_max_dies()))
>  				continue;
>  
>  			parse_discovery_table(domain, dev, die, bar_offset, &parsed);

Reviewed-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>