linux-kernel - Re: [PATCH v3 08/10] x86/mtrr: let cache_aps_delayed_init replace mtrr_aps_delayed

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Date:   Wed, 28 Sep 2022 13:22:51 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Juergen Gross <jgross@...e.com>
Cc:     xen-devel@...ts.xenproject.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v3 08/10] x86/mtrr: let cache_aps_delayed_init replace
 mtrr_aps_delayed_init

On Wed, Sep 28, 2022 at 01:14:11PM +0200, Juergen Gross wrote:
> No, we don't.
> 
> Using basically your patch, but with
> 
> +	mtrr_online = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
> +						"x86/mtrr:online",
> +						mtrr_ap_init, NULL);
> 
> moved to the end of mtrr_aps_init(), and:
> 
> +void mtrr_aps_thaw(void)
> +{
> +	cpuhp_remove_state_nocalls(mtrr_online);
> +}

Yes, so you said. I'm not sure I like this toggling of notifier
registration like that.

Optimally, I'd like to be able to query the suspend code whether it is
in the process of resuming.

This here:


static int resume_target_kernel(bool platform_mode)
{

...

 Enable_irqs:
        system_state = SYSTEM_RUNNING;
        local_irq_enable();
 
 Enable_cpus:
        pm_sleep_enable_secondary_cpus();


but being able to do:

        pm_sleep_enable_secondary_cpus();
	system_state = SYSTEM_RUNNING | SYSTEM_RUNNING_APS_UP;

which can't work, obviously. But something like that.

-- 
Regards/Gruss,
    Boris.

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