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

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Date:   Fri, 14 Oct 2016 16:42:31 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Laszlo Ersek <lersek@...hat.com>
Cc:     Andrew Jones <drjones@...hat.com>,
        Zhen Lei <thunder.leizhen@...wei.com>,
        Will Deacon <will.deacon@....com>,
        Hanjun Guo <hanjun.guo@...aro.org>,
        main kernel list <linux-kernel@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Shannon Zhao <shannon.zhao@...aro.org>,
        Wei Huang <wei@...hat.com>
Subject: Re: aarch64 ACPI boot regressed by commit 7ba5f605f3a0 ("arm64/numa:
 remove the limitation that cpu0 must bind to node0")

On Fri, Oct 14, 2016 at 05:27:58PM +0200, Laszlo Ersek wrote:
> 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".

Yes, because that's to check the MADT contains the boot cpu hwid.

Does this help (compile tested only) ?

-- >8 -- 
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index d3f151c..8507703 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -544,6 +544,7 @@ static int __init smp_cpu_setup(int cpu)
 			return;
 		}
 		bootcpu_valid = true;
+		early_map_cpu_to_node(0, acpi_numa_get_nid(0, hwid));
 		return;
 	}