[PATCH V4 3/4] perf/x86/intel/uncore: Fix die ID init and look up bugs

Zide Chen
2026-03-13T17:50:43Z

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.

V4: 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 786bd51a0d89..e9cc1ba921c5 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 9b51883fd6fd..421378f681d7 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.
--
2.53.0