linux-kernel - Re: [PATCH v9 0/8] Parallel CPU bringup for x86

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Message-ID: <9153284c37a79d303aa79dbf07c10329@natalenko.name>
Date:   Tue, 21 Feb 2023 13:14:07 +0100
From:   Oleksandr Natalenko <oleksandr@...alenko.name>
To:     David Woodhouse <dwmw2@...radead.org>
Cc:     Kim Phillips <kim.phillips@....com>, tglx@...utronix.de,
        Usama Arif <usama.arif@...edance.com>, arjan@...ux.intel.com,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        hpa@...or.com, x86@...nel.org, pbonzini@...hat.com,
        paulmck@...nel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, rcu@...r.kernel.org, mimoja@...oja.de,
        hewenliang4@...wei.com, thomas.lendacky@....com, seanjc@...gle.com,
        pmenzel@...gen.mpg.de, fam.zheng@...edance.com,
        punit.agrawal@...edance.com, simon.evans@...edance.com,
        liangma@...ngbit.com,
        "Limonciello, Mario" <Mario.Limonciello@....com>,
        Piotr Gorski <piotrgorski@...hyos.org>
Subject: Re: [PATCH v9 0/8] Parallel CPU bringup for x86_64

On 21.02.2023 12:49, David Woodhouse wrote:
> On 21 February 2023 11:46:04 GMT, Oleksandr Natalenko 
> <oleksandr@...alenko.name> wrote:
>> On 21.02.2023 11:27, David Woodhouse wrote:
>>> On 21 February 2023 09:49:51 GMT, Oleksandr Natalenko 
>>> <oleksandr@...alenko.name> wrote:
>>>> On 21.02.2023 10:06, David Woodhouse wrote:
>>>>> Why does arch/x86/kernel/acpi/sleep.c::x86_acpi_suspend_lowlevel() 
>>>>> set
>>>>> 
>>>>>     initial_gs = per_cpu_offset(smp_processor_id()) ?
>>>>> 
>>>>> Would it not be CPU#0 that comes back up, and should it not get
>>>>> per_cpu_offset(0) ?
>>>> 
>>>> Wanna me try `initial_gs = per_cpu_offset(0);` too?
>>> 
>>> Hm, yes please. There's another one to make zero on the next line up, 
>>> I think?
>> 
>> So,
>> 
>> ```
>> early_gdt_descr.address = (unsigned long)get_cpu_gdt_rw(0);
>> initial_gs = per_cpu_offset(0);
>> ```
>> 
>> ?
>> 
>> Should I leave `smpboot_control = 0;` commented out, or I should 
>> uncomment it back?
> 
> Put it back, else those things don't matter. Thanks.

With this in place:

```
	early_gdt_descr.address = (unsigned long)get_cpu_gdt_rw(0);
	initial_gs = per_cpu_offset(0);
	smpboot_control = 0;
```

the resume does not work.

-- 
   Oleksandr Natalenko (post-factum)