Messages in this thread | | | Date | Tue, 11 Jul 2023 16:07:55 -0700 | Subject | Re: [PATCH] x86/platform/uv: Abort UV initialization when reduced nr_cpus requires it | From | Dave Hansen <> |
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On 7/11/23 13:26, Steve Wahl wrote: > When nr_cpus is set to a smaller number than actually present, there > is some node-to-socket mapping info we won't get access to in
First of all, no "we's" in commit messages.
> https://www.kernel.org/doc/html/next/process/maintainer-tip.html#changelog
> build_socket_tables(). This could later result in using a -1 value > for some array indexing, and eventual kernel page faults. > > To avoid this, if any unfilled table entries are found, print a > warning message, and resume initializing, acting as if this is not a > UV system. UV features will be unavailable, but we will not cause > kernel dumps. > > This is a condition we expect only in platform debugging situations, > not in day-to-day operation.
This seems like a hack.
The real problem is that you've got an online Linux NUMA node with no CPUs. uv_system_init_hub() (probably) goes and does:
> for_each_node(nodeid) > __uv_hub_info_list[nodeid] = uv_hub_info_list_blade[uv_node_to_blade_id(nodeid)];
But the node=>blade lookup uses socket numbers. No CPUs means no socket numbers. You _have_ the blade information _somewhere_. Is there really no other way to map it to a NUMA node than using the CPU apicid?
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