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

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Message-ID: <3e5944de08ef0d23584d19bad7bae66c@natalenko.name>
Date:   Tue, 21 Feb 2023 10:49:51 +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 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?

> Or maybe we should just set up smpboot_control for the CPU to find its
> own stuff, *even* on waking. Since the structures are already set up,
> it isn't like a clean boot.
> 
> If you let it boot in parallel mode, what if you just *remove* the line
> that sets smpboot_control=0 ?

If the `smpboot_control = 0;` line in 
arch/x86/kernel/acpi/sleep.c::x86_acpi_suspend_lowlevel() is commented 
out, and the system is booted in parallel mode, then suspend/resume 
works.

-- 
   Oleksandr Natalenko (post-factum)