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 08:16:53 +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 07:30, Juergen Gross wrote:
> On 28.09.22 01:16, Borislav Petkov wrote:
>> On Tue, Sep 27, 2022 at 02:21:17PM +0200, Juergen Gross wrote:
>>> So replacing the bool with "(system_state != SYSTEM_RUNNING)" is fine
>>> with you right now? We can later switch that to the "more elegant"
>>> solution when it shows up.
>>
>> Ok, I think I have something. And it was staring me straight in the
>> face but I didn't see it: the MTRR code needs a hotplug notifier. In
>> that notifier it can do the immediate, i.e., non-delayed init while the
>> delayed init becomes the default, see below.
>>
>> And ignore the pr_info debugging gunk pls.
>>
>> mtrr_ap_init() becomes the notifier callback. It doesn't need to be
>> called in identify_secondary_cpu() anymore as in the init case that
>> function doesn't do anything - delayed=true - and in the hotplug case
>> the notifier runs.
> 
> Are sure the hotplug notifier doesn't get called in the boot and in the
> resume cases? I don't see how those calls are being not done or resulting in
> not doing anything.

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().


Juergen


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