linux-kernel - Re: [PATCH v6 04/11] x86/smpboot: Reference count on smpboot_setup_warm_reset

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Date:   Tue, 07 Feb 2023 00:48:40 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Usama Arif <usama.arif@...edance.com>, dwmw2@...radead.org,
        arjan@...ux.intel.com
Cc:     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, David Woodhouse <dwmw@...zon.co.uk>,
        Usama Arif <usama.arif@...edance.com>
Subject: Re: [PATCH v6 04/11] x86/smpboot: Reference count on
 smpboot_setup_warm_reset_vector()

On Thu, Feb 02 2023 at 21:56, Usama Arif wrote:
> From: David Woodhouse <dwmw@...zon.co.uk>
>
> If we want to do parallel CPU bringup, we're going to need to set this up
> and leave it until all CPUs are done. Might as well use the RTC spinlock
> to protect the refcount, as we need to take it anyway.

https://www.kernel.org/doc/html/latest/process/maintainer-tip.html#changelog

Aside of the 'We' this does not explain anything at all.

> [Usama Arif: fixed rebase conflict]
> Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
> Signed-off-by: Usama Arif <usama.arif@...edance.com>
> Signed-off-by: Paul E. McKenney <paulmck@...nel.org>

This SOB chain is even more broken...

> ---
>  arch/x86/kernel/smpboot.c | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index 55cad72715d9..a19eddcdccc2 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -121,17 +121,22 @@ int arch_update_cpu_topology(void)
>  	return retval;
>  }
>  
> +
> +static unsigned int smpboot_warm_reset_vector_count;
> +
>  static inline void smpboot_setup_warm_reset_vector(unsigned long start_eip)
>  {
>  	unsigned long flags;
>  
>  	spin_lock_irqsave(&rtc_lock, flags);
> -	CMOS_WRITE(0xa, 0xf);
> +	if (!smpboot_warm_reset_vector_count++) {
> +		CMOS_WRITE(0xa, 0xf);
> +		*((volatile unsigned short *)phys_to_virt(TRAMPOLINE_PHYS_HIGH)) =
> +			start_eip >> 4;
> +		*((volatile unsigned short *)phys_to_virt(TRAMPOLINE_PHYS_LOW)) =
> +			start_eip & 0xf;

Again: 80 characters are history. Please fix that all over the series.

Thanks,

        tglx