Re: [PATCH v3 08/10] x86/mtrr: let cache_aps_delayed_init replace mtrr_aps_delayed_init

From: Juergen Gross <jgross@suse.com>
To: Borislav Petkov <bp@alien8.de>
Cc: xen-devel@lists.xenproject.org, x86@kernel.org,
	linux-kernel@vger.kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH v3 08/10] x86/mtrr: let cache_aps_delayed_init replace mtrr_aps_delayed_init
Date: Wed, 28 Sep 2022 08:16:53 +0200	[thread overview]
Message-ID: <24088a15-50a1-f818-8c3e-6010925bffbf@suse.com> (raw)
In-Reply-To: <73d8fabd-8b93-2e65-da4b-ea509818e666@suse.com>

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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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