Overview

A customer may report that while reviewing their logs, the following errors are present:

• Kernel: ACPI: Warning: 0x00000000000004000-0x000000000000401f SystemIO conflicts with Region \_SB_PCI0.SBUS.SMBI 1 (20120320/utaddress-251)
• Kernel: ACPI: This conflict may cause random problems and system instability

This article provides detail about the meaning of these messages, and how to provide this information to our customers when they inquire about it.

Root Cause

These errors refer to SMBus. The SMBus is a reduced functionality I2C bus used to communicate with sensors such as temperature and voltage sensors etc. and to read and set switches and relays, etc.

• For the error "Kernel: ACPI: Warning: 0x00000000000004000-0x000000000000401f SystemIO conflicts with Region \_SB_PCI0.SBUS.SMBI 1 (20120320/utaddress-251)."
  The ACPI claims these I/O addresses as belong to ACPI, and PNP claims the same I/O addresses as belonging to it.
• For the error "Kernel: ACPI: This conflict may cause random problems and system instability."
  This can happen only if two things are trying to talk to the same I/O addresses at the same time.

Information

We do not talk to any of these sensors (we *used* to use them for temperature, but these days we use the sensors built into the CPU's). If we had something saying 'I can talk to these sensors that ACPI said exists' and another thing that said 'I can talk to these sensors that PNP said exists' then we would have problems, but we have nothing talking to any of these sensors.

The Linux Kernel developers enabled this warning to try and get people to star, ensuring that each resource is only exposed once to user-space (rather than twice like this SMBus resource is.). So it is not important in this case, and this does not refer to any hardware problem.