linux-kernel - Re: [PATCH 2/2] perf/x86/intel/uncore: Fix die ID init and look up bugs

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Message-ID: <926de635-35ae-4ac9-b235-2d394f20ae7e@linux.intel.com>
Date: Thu, 30 Oct 2025 09:39:19 +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 2/2] perf/x86/intel/uncore: Fix die ID init and look up
 bugs


On 10/30/2025 6:07 AM, Zide Chen wrote:
> In snbep_pci2phy_map_init(), if there are more than 8 nodes,
> uncore_device_to_die(ubox_dev) may return -1 if all CPUs
> associated with the UBOX device are offline.  This is not an error
> and we still need to populate map->pbus_to_dieid[].
>
> If NUMA is disabled on a NUMA-capable platform, pcibus_to_node()
> returns NUMA_NO_NODE and uncore_device_to_die() returns -1.  As a
> result, in spr_update_device_location(), which is used on Intel SPR,
> GNR etc., the PMON units are ignored and not added to the RB tree.

It seems spr_update_device_location() currently is only called by SPR,
please double check. 

BTW, is this a SPR specific issue or a common issue? Thanks.


>
> Use uncore_pcibus_to_dieid() instead, which retrieves topology
> information from the GIDNIDMAP register of the UBOX device.
>
> Fixes: 9a7832ce3d92 ("perf/x86/intel/uncore: With > 8 nodes, get pci bus die id from NUMA info")
> Fixes: 65248a9a9ee1 ("perf/x86/uncore: Add a quirk for UPI on SPR")
> Signed-off-by: Zide Chen <zide.chen@...el.com>
> ---
>  arch/x86/events/intel/uncore.c       |  1 +
>  arch/x86/events/intel/uncore_snbep.c | 13 ++++++-------
>  2 files changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
> index 5c3aeea5c78d..84d6e481f18f 100644
> --- a/arch/x86/events/intel/uncore.c
> +++ b/arch/x86/events/intel/uncore.c
> @@ -77,6 +77,7 @@ int uncore_die_to_segment(int die)
>  	return bus ? pci_domain_nr(bus) : -EINVAL;
>  }
>  
> +/* Note: This API can only be used when NUMA information is available. */
>  int uncore_device_to_die(struct pci_dev *dev)
>  {
>  	int node = pcibus_to_node(dev->bus);
> diff --git a/arch/x86/events/intel/uncore_snbep.c b/arch/x86/events/intel/uncore_snbep.c
> index ad4d11762ecf..e68467f617f9 100644
> --- a/arch/x86/events/intel/uncore_snbep.c
> +++ b/arch/x86/events/intel/uncore_snbep.c
> @@ -1471,13 +1471,7 @@ static int snbep_pci2phy_map_init(int devid, int nodeid_loc, int idmap_loc, bool
>  			}
>  
>  			map->pbus_to_dieid[bus] = die_id = uncore_device_to_die(ubox_dev);
> -
>  			raw_spin_unlock(&pci2phy_map_lock);
> -
> -			if (WARN_ON_ONCE(die_id == -1)) {
> -				err = -EINVAL;
> -				break;
> -			}
>  		}
>  	}
>  
> @@ -6530,7 +6524,7 @@ static void spr_update_device_location(int type_id)
>  
>  	while ((dev = pci_get_device(PCI_VENDOR_ID_INTEL, device, dev)) != NULL) {
>  
> -		die = uncore_device_to_die(dev);
> +		die = uncore_pcibus_to_dieid(dev->bus);
>  		if (die < 0)
>  			continue;
>  
> @@ -6554,6 +6548,11 @@ static void spr_update_device_location(int type_id)
>  
>  int spr_uncore_pci_init(void)
>  {
> +	int ret = snbep_pci2phy_map_init(0x3250, SKX_CPUNODEID, SKX_GIDNIDMAP, true);
> +
> +	if (ret)
> +		return ret;
> +
>  	/*
>  	 * The discovery table of UPI on some SPR variant is broken,
>  	 * which impacts the detection of both UPI and M3UPI uncore PMON.