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

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

[Zide Chen]

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@hpe.com>
Tested-by: Steve Wahl <steve.wahl@hpe.com>
Fixes: edae1f06c2cd ("perf/x86/intel/uncore: Parse uncore discovery tables")
Signed-off-by: Zide Chen <zide.chen@intel.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);
-- 
2.52.0

[PATCH V3 2/2] perf/x86/intel/uncore: Fix die ID init and look up bugs

[Zide Chen]

In snbep_pci2phy_map_init(), in the nr_node_ids > 8 path,
uncore_device_to_die() may return -1 when all CPUs associated
with the UBOX device are offline.

Remove the WARN_ON_ONCE(die_id == -1) check for two reasons:

- The current code breaks out of the loop. This is incorrect because
  pci_get_device() does not guarantee iteration in domain or bus order,
  so additional UBOX devices may be skipped during the scan.

- Returning -EINVAL is incorrect, since marking offline buses with
  die_id == -1 is expected and should not be treated as an error.

Separately, when NUMA is disabled on a NUMA-capable platform,
pcibus_to_node() returns NUMA_NO_NODE, causing uncore_device_to_die()
to return -1 for all PCI devices.  As a result,
spr_update_device_location(), used on Intel SPR and EMR, ignores the
corresponding PMON units and does not add them to the RB tree.

Fix this by using uncore_pcibus_to_dieid(), which retrieves topology
from the UBOX GIDNIDMAP register and works regardless of whether NUMA
is enabled in Linux.  This requires snbep_pci2phy_map_init() to be
added in spr_uncore_pci_init().

Keep uncore_device_to_die() only for the nr_node_ids > 8 case, where
NUMA is expected to be enabled.

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")
Tested-by: Steve Wahl <steve.wahl@hpe.com>
Signed-off-by: Zide Chen <zide.chen@intel.com>
---
V2:
- Fix the commit message to note that spr_update_device_location() is
  used by EMR, not GNR.
- Rewrite the commit message for clarity.
- Add a Tested-by tag.

V3: no changes

 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 4684649109d9..94592de6431a 100644
--- a/arch/x86/events/intel/uncore.c
+++ b/arch/x86/events/intel/uncore.c
@@ -67,6 +67,7 @@ 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 7ca0429c4004..52dec34d18c4 100644
--- a/arch/x86/events/intel/uncore_snbep.c
+++ b/arch/x86/events/intel/uncore_snbep.c
@@ -1459,13 +1459,7 @@ 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;
-			}
 		}
 	}
 
@@ -6420,7 +6414,7 @@ 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;
 
@@ -6444,6 +6438,11 @@ 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.
-- 
2.52.0

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

[Mi, Dapeng]

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@hpe.com>
> Tested-by: Steve Wahl <steve.wahl@hpe.com>
> Fixes: edae1f06c2cd ("perf/x86/intel/uncore: Parse uncore discovery tables")
> Signed-off-by: Zide Chen <zide.chen@intel.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@linux.intel.com>

Re: [PATCH V3 2/2] perf/x86/intel/uncore: Fix die ID init and look up bugs

[Mi, Dapeng]

On 1/16/2026 11:11 AM, Zide Chen wrote:
> In snbep_pci2phy_map_init(), in the nr_node_ids > 8 path,
> uncore_device_to_die() may return -1 when all CPUs associated
> with the UBOX device are offline.
>
> Remove the WARN_ON_ONCE(die_id == -1) check for two reasons:
>
> - The current code breaks out of the loop. This is incorrect because
>   pci_get_device() does not guarantee iteration in domain or bus order,
>   so additional UBOX devices may be skipped during the scan.
>
> - Returning -EINVAL is incorrect, since marking offline buses with
>   die_id == -1 is expected and should not be treated as an error.
>
> Separately, when NUMA is disabled on a NUMA-capable platform,
> pcibus_to_node() returns NUMA_NO_NODE, causing uncore_device_to_die()
> to return -1 for all PCI devices.  As a result,
> spr_update_device_location(), used on Intel SPR and EMR, ignores the
> corresponding PMON units and does not add them to the RB tree.
>
> Fix this by using uncore_pcibus_to_dieid(), which retrieves topology
> from the UBOX GIDNIDMAP register and works regardless of whether NUMA
> is enabled in Linux.  This requires snbep_pci2phy_map_init() to be
> added in spr_uncore_pci_init().
>
> Keep uncore_device_to_die() only for the nr_node_ids > 8 case, where
> NUMA is expected to be enabled.
>
> 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")
> Tested-by: Steve Wahl <steve.wahl@hpe.com>
> Signed-off-by: Zide Chen <zide.chen@intel.com>
> ---
> V2:
> - Fix the commit message to note that spr_update_device_location() is
>   used by EMR, not GNR.
> - Rewrite the commit message for clarity.
> - Add a Tested-by tag.
>
> V3: no changes
>
>  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 4684649109d9..94592de6431a 100644
> --- a/arch/x86/events/intel/uncore.c
> +++ b/arch/x86/events/intel/uncore.c
> @@ -67,6 +67,7 @@ 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 7ca0429c4004..52dec34d18c4 100644
> --- a/arch/x86/events/intel/uncore_snbep.c
> +++ b/arch/x86/events/intel/uncore_snbep.c
> @@ -1459,13 +1459,7 @@ 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;
> -			}
>  		}
>  	}
>  
> @@ -6420,7 +6414,7 @@ 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;
>  
> @@ -6444,6 +6438,11 @@ 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.

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