linux-kernel - Re: [PATCH v15 04/12] x86/smpboot: Reference count on smpboot_setup_warm_reset

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Message-ID: <20230321114115.GGZBmX270DI11eXvM+@fat_crate.local>
Date:   Tue, 21 Mar 2023 12:41:15 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Usama Arif <usama.arif@...edance.com>
Cc:     dwmw2@...radead.org, tglx@...utronix.de, kim.phillips@....com,
        brgerst@...il.com, piotrgorski@...hyos.org,
        oleksandr@...alenko.name, arjan@...ux.intel.com, mingo@...hat.com,
        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,
        gpiccoli@...lia.com, David Woodhouse <dwmw@...zon.co.uk>
Subject: Re: [PATCH v15 04/12] x86/smpboot: Reference count on
 smpboot_setup_warm_reset_vector()

On Thu, Mar 16, 2023 at 10:21:01PM +0000, Usama Arif wrote:
> From: David Woodhouse <dwmw@...zon.co.uk>
> 
> When bringing up a secondary CPU from do_boot_cpu(), the warm reset flag
> is set in CMOS and the starting IP for the trampoline written inside the
> BDA at 0x467. Once the CPU is running, the CMOS flag is unset and the
> value in the BDA cleared.
> 
> To allow for parallel bringup of CPUs, add a reference count to track the
> number of CPUs currently bring brought up, and clear the state only when

s/bring //

> the count reaches zero.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette