linux-kernel - Re: [patch 00/37] cpu/hotplug, x86: Reworked parallel CPU bringup

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Date:   Wed, 19 Apr 2023 18:45:03 +0200
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        David Woodhouse <dwmw2@...radead.org>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Brian Gerst <brgerst@...il.com>,
        Arjan van de Veen <arjan@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Paul McKenney <paulmck@...nel.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Sean Christopherson <seanjc@...gle.com>,
        Oleksandr Natalenko <oleksandr@...alenko.name>,
        "Guilherme G. Piccoli" <gpiccoli@...lia.com>,
        Piotr Gorski <lucjan.lucjanov@...il.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Usama Arif <usama.arif@...edance.com>,
        Jürgen Groß <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xenproject.org,
        Russell King <linux@...linux.org.uk>,
        Arnd Bergmann <arnd@...db.de>,
        linux-arm-kernel@...ts.infradead.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Guo Ren <guoren@...nel.org>,
        linux-csky@...r.kernel.org,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-mips@...r.kernel.org,
        "James E. J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Helge Deller <deller@....de>, linux-parisc@...r.kernel.org,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        linux-riscv@...ts.infradead.org,
        Mark Rutland <mark.rutland@....com>,
        Sabin Rapan <sabrapan@...zon.com>
Subject: Re: [patch 00/37] cpu/hotplug, x86: Reworked parallel CPU bringup

Dear Thomas,


Am 19.04.23 um 14:38 schrieb Thomas Gleixner:
> On Wed, Apr 19 2023 at 11:38, Thomas Gleixner wrote:
>> On Tue, Apr 18 2023 at 22:10, Paul Menzel wrote:
>>> Am 18.04.23 um 10:40 schrieb Thomas Gleixner:
>>>> Can you please provide the output of cpuid?
>>>
>>> Of course. Here the top, and the whole output is attached.
>>
>> Thanks for the data. Can you please apply the debug patch below and
>> provide the dmesg output? Just the line which is added by the patch is
>> enough. You can boot with cpuhp.parallel=off so you don't have wait for
>> 10 seconds.
> 
> Borislav found some a machine which also refuses to boot. It turns of
> the debug patch was spot on:
> 
> [    0.462724] .... node  #0, CPUs:      #1
> [    0.462731] smpboot: Kicking AP alive: 17
> [    0.465723]  #2
> [    0.465732] smpboot: Kicking AP alive: 18
> [    0.467641]  #3
> [    0.467641] smpboot: Kicking AP alive: 19
> 
> So the kernel gets APICID 17, 18, 19 from ACPI but CPUID leaf 0x1
> ebx[31:24], which is the initial APICID has:
> 
> CPU1		0x01
> CPU2		0x02
> CPU3		0x03
> 
> Which means the APICID to Linux CPU number lookup based on CPUID 0x01
> fails for all of them and stops them dead in the low level startup code.

I am attaching the logs for completeness. Linux is build from your 
branch with the debug print on top. The firmware, coreboot based, is 
built from [1], but it also happened non-parallel MP init. The code has 
better debug prints (attached) though as far as I can see. As Borislav 
is able to reproduce this too with some non-coreboot firmware, I assume 
it’s unrelated to coreboot.

```
[    0.259247] smp: Bringing up secondary CPUs ...
[    0.259446] x86: Booting SMP configuration:
[    0.259448] .... node  #0, CPUs:      #1
[    0.259453] smpboot: Kicking AP alive: 17
[   10.260918] CPU1 failed to report alive state
[   10.260998] smp: Brought up 1 node, 1 CPU
[   10.261000] smpboot: Max logical packages: 2
[   10.261001] smpboot: Total of 1 processors activated (7801.09 BogoMIPS)
```

> IOW, the BIOS assignes random numbers to the AP APICs for whatever
> raisins, which leaves the parallel startup low level code up a creek
> without a paddle, except for actually reading the APICID back from the
> APIC. *SHUDDER*
> 
> I'm leaning towards disabling the CPUID lead 0x01 based discovery and be
> done with it.


Kind regards,

Paul


[1]: https://review.coreboot.org/68169
View attachment "kodi-linux-6.3-rc3-smp-tglx.txt" of type "text/plain" (57422 bytes)

View attachment "20230419-coreboot-cbmem-log-cb-68169.txt" of type "text/plain" (32882 bytes)