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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Message-ID: <20161014165835.GA24546@red-moon>
Date:   Fri, 14 Oct 2016 17:58:35 +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 06:22:55PM +0200, Laszlo Ersek wrote:
> On 10/14/16 17:42, Lorenzo Pieralisi wrote:
> > 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;
> >  	}
> >  
> > 
> 
> Your patch applies to the tree at v4.8-14604-g29fbff8698fc, but the function the hunk modifies is not smp_cpu_setup(), it is acpi_map_gic_cpu_interface():
> 
> > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> > index d3f151cfd4a1..8507703dabe4 100644
> > --- a/arch/arm64/kernel/smp.c
> > +++ b/arch/arm64/kernel/smp.c
> > @@ -544,6 +544,7 @@ acpi_map_gic_cpu_interface(struct acpi_madt_generic_interrupt *processor)
> >  			return;
> >  		}
> >  		bootcpu_valid = true;
> > +		early_map_cpu_to_node(0, acpi_numa_get_nid(0, hwid));
> >  		return;
> >  	}
> > 
> 
> Anyway, your patch works with both the two-node NUMA configuration
> Drew suggested for testing, and with the single-node config that I
> originally used for the bisection. Therefore:
> 
> Tested-by: Laszlo Ersek <lersek@...hat.com>
> Reported-by: Laszlo Ersek <lersek@...hat.com>
> 
> Thank you very much for the quick bugfix! And, I think your patch
> (when you send it for real) should carry
> 
> Fixes: 7ba5f605f3a0d9495aad539eeb8346d726dfc183
> 
> too, because it supplies the cpu#0<->node#xxx association that
> 7ba5f605f3a0 removed not just for DT, but also for ACPI.

Sure, will do, I will send it out on Monday.

Cheers,
Lorenzo