From: Kan Liang kan.liang@linux.intel.com
commit 4a0e3ff30980b7601b13dd3b7ee275212b852843 upstream.
A kernel WARNING may be triggered when setting maxcpus=1.
The uncore counters are Die-scope. When probing a PCI device, only the BUS information can be retrieved. The uncore driver has to maintain a mapping table used to calculate the logical Die ID from a given BUS#.
Before the patch ba9506be4e40, the mapping table stores the mapping information from the BUS# -> a Physical Socket ID. To calculate the logical die ID, perf does, - In snbep_pci2phy_map_init(), retrieve the BUS# -> a Physical Socket ID from the UBOX PCI configure space. - Calculate the mapping information (a BUS# -> a Physical Socket ID) for the other PCI BUS. - In the uncore_pci_probe(), get the physical Socket ID from a given BUS and the mapping table. - Calculate the logical Die ID
Since only the logical Die ID is required, with the patch ba9506be4e40, the mapping table stores the mapping information from the BUS# -> a logical Die ID. Now perf does, - In snbep_pci2phy_map_init(), retrieve the BUS# -> a Physical Socket ID from the UBOX PCI configure space. - Calculate the logical Die ID - Calculate the mapping information (a BUS# -> a logical Die ID) for the other PCI BUS. - In the uncore_pci_probe(), get the logical die ID from a given BUS and the mapping table.
When calculating the logical Die ID, -1 may be returned, especially when maxcpus=1. Here, -1 means the logical Die ID is not found. But when calculating the mapping information for the other PCI BUS, -1 indicates that it's the other PCI BUS that requires the calculation of the mapping. The driver will mistakenly do the calculation.
Uses the -ENODEV to indicate the case which the logical Die ID is not found. The driver will not mess up the mapping table anymore.
Fixes: ba9506be4e40 ("perf/x86/intel/uncore: Store the logical die id instead of the physical die id.") Reported-by: John Donnelly john.p.donnelly@oracle.com Signed-off-by: Kan Liang kan.liang@linux.intel.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Acked-by: John Donnelly john.p.donnelly@oracle.com Tested-by: John Donnelly john.p.donnelly@oracle.com Link: https://lkml.kernel.org/r/1622037527-156028-1-git-send-email-kan.liang@linux... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/events/intel/uncore_snbep.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
--- a/arch/x86/events/intel/uncore_snbep.c +++ b/arch/x86/events/intel/uncore_snbep.c @@ -1406,6 +1406,8 @@ static int snbep_pci2phy_map_init(int de die_id = i; else die_id = topology_phys_to_logical_pkg(i); + if (die_id < 0) + die_id = -ENODEV; map->pbus_to_dieid[bus] = die_id; break; } @@ -1452,14 +1454,14 @@ static int snbep_pci2phy_map_init(int de i = -1; if (reverse) { for (bus = 255; bus >= 0; bus--) { - if (map->pbus_to_dieid[bus] >= 0) + if (map->pbus_to_dieid[bus] != -1) i = map->pbus_to_dieid[bus]; else map->pbus_to_dieid[bus] = i; } } else { for (bus = 0; bus <= 255; bus++) { - if (map->pbus_to_dieid[bus] >= 0) + if (map->pbus_to_dieid[bus] != -1) i = map->pbus_to_dieid[bus]; else map->pbus_to_dieid[bus] = i;