Re: aarch64 ACPI boot regressed by commit 7ba5f605f3a0 ("arm64/numa: remove the limitation that cpu0 must bind to node0")

From: Laszlo Ersek
Date: Fri Oct 14 2016 - 11:28:11 EST

On 10/14/16 17:01, Laszlo Ersek wrote:

> Maybe the code I
> tried to analyze in this email was never *meant* to associate CPU#0 with
> any NUMA node at all (not even node 0); instead, other code -- for
> example code removed by 7ba5f605f3a0 -- was meant to perform that
> association.

Staring a bit more at the code, this looks very likely; in acpi_map_gic_cpu_interface() we have

> /* Check if GICC structure of boot CPU is available in the MADT */
> if (cpu_logical_map(0) == hwid) {
> if (bootcpu_valid) {
> pr_err("duplicate boot CPU MPIDR: 0x%llx in MADT\n",
> hwid);
> return;
> }
> bootcpu_valid = true;
> return;
> }

which means that this callback function (for parsing the GICC structures in the MADT) expects to find the boot processor as well.

Upon finding the boot processor, we set bootcpu_valid to true, and that's it -- no association with any NUMA node, and no incrementing of "cpu_count".