Commit a16d1ec4 authored Mar 13, 2026 by Zide Chen Committed by Peter Zijlstra Apr 07, 2026

perf/x86/intel/uncore: Fix die ID init and look up bugs



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: 9a7832ce ("perf/x86/intel/uncore: With > 8 nodes, get pci bus die id from NUMA info")
Fixes: 65248a9a ("perf/x86/uncore: Add a quirk for UPI on SPR")
Signed-off-by: Zide Chen <zide.chen@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Tested-by: Steve Wahl <steve.wahl@hpe.com>
Link: https://patch.msgid.link/20260313174050.171704-4-zide.chen@intel.com

parent 7b568e9e

arch/x86/events/intel/uncore.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -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);

arch/x86/events/intel/uncore_snbep.c

+6 −7

Original line number	Diff line number	Diff line
		@@ -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.