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 13:14:11 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Borislav Petkov <bp@...en8.de>
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 28.09.22 12:48, Borislav Petkov wrote:
> On Wed, Sep 28, 2022 at 08:16:53AM +0200, Juergen Gross wrote:
>>> Are sure the hotplug notifier doesn't get called in the boot and in the
> 
> It doesn't because it gets registered after smp_init()...
> 
>>> resume cases?
> 
> ... but it gets called during resume because by that time the notifier
> has been registered already. See my notes at the end of this mail of
> what the code does currently.
> 
>> In case my suspicion is correct: this can still be solved by adding the
>> hotplug notifier only in mtrr_aps_init(), and removing it again in
>> arch_thaw_secondary_cpus_begin().
> 
> Pretty much. Yeah, we still need a bool. ;-(

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);
+}


Juergen

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