On 2020/7/18 1:59, Jonathan Cameron wrote:
Here, I will use the term Proximity Domains for the ACPI description and NUMA Nodes for the in kernel representation. ACPI 6.3 included a clarification that only Static Resource Allocation Structures in SRAT may define the existence of proximity domains (sec 5.2.16). This clarification closed a possible interpretation that other parts of ACPI (e.g. DSDT _PXM, NFIT etc) could define new proximity domains that were not also mentioned in SRAT structures. In practice the kernel has never allowed this alternative interpretation as such nodes are only partially initialized. This is architecture specific but to take an example, on x86 alloc_node_data has not been called. Any use of them for node specific allocation, will result in a crash as the infrastructure to fallback to a node with memory is not setup. We ran into a problem when enabling _PXM handling for PCI devices and found there were boards out there advertising devices in proximity domains that didn't exist [2]. The fix suggested in this series is to replace instances that should not 'create' new nodes with pxm_to_node. This function needs a some additional hardening against invalid inputs to make sure it is safe for use in these new callers. Patch 1 Hardens pxm_to_node() against numa_off, and pxm entry being too large. Patch 2-4 change the various callers not related to SRAT entries so that they set this parameter to false, so do not attempt to initialize a new NUMA node if the relevant one does not already exist. Patch 5 is a function rename to reflect change in functionality of acpi_map_pxm_to_online_node() as it no longer creates a new map, but just does a lookup of existing maps. Patch 6 covers the one place we do not allow the full flexibility defined in the ACPI spec. For SRAT GIC Interrupt Translation Service (ITS) Affinity Structures, on ARM64, the driver currently makes an additional pass of SRAT later in the boot than the one used to identify NUMA domains. Note, this currently means that an ITS placed in a proximity domain that is not defined by another SRAT structure will result in the a crash. To avoid this crash with minimal changes we do not create new NUMA nodes based on this particular entry type. Any current platform trying to do this will not boot, so this is an improvement, if perhaps not a perfect solution.
Make sense to me, Reviewed-by: Hanjun Guo <guohanjun@xxxxxxxxxx>
