aa2ddd2425
There is a problem in mapping CPU to a PCI device instance when the bus numbers are reused in different packages. This was observed on some Sapphire Rapids systems. The current implementation reads bus number assigned to a CPU package via MSR 0x128. This allows to establish relationship between a CPU and a PCI device. This allows to update power related parameters to a MMIO offset in a PCI device space which is unique to a CPU. But if two packages uses same bus number then this mapping will not be unique. When bus number is reused, PCI device will use different domain number or segment number. So we need to be aware of this domain information while matching CPU to PCI bus number. This domain information is not available via any MSR. So need to use ACPI numa node information. There is an interface already available in the Linux to read numa node for a CPU and a PCI device. This change uses this interface to check the numa node of a match PCI device with bus number. If the bus number and numa node matches with the CPU's assigned bus number and numa node, the matched PCI device instance will be returned to the caller. It is possible that before Sapphire Rapids, the numa node is not defined for the Speed Select PCI device in some OEM systems. In this case to restore old behavior, return the last matched PCI device for domain 0 unlsess there are more than one matches. Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Link: https://lore.kernel.org/r/20210616221329.1909276-2-srinivas.pandruvada@linux.intel.com Reviewed-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.