linux-kernel - Re: [PATCH v5 07/12] x86/cpu/keylocker: Load an internal wrapping key at boot-time

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Date:   Wed, 24 Aug 2022 15:20:59 -0700
From:   "Chang S. Bae" <chang.seok.bae@...el.com>
To:     Evan Green <evgreen@...omium.org>
CC:     <linux-crypto@...r.kernel.org>, <dm-devel@...hat.com>,
        <herbert@...dor.apana.org.au>, Eric Biggers <ebiggers@...nel.org>,
        "Ard Biesheuvel" <ardb@...nel.org>, <x86@...nel.org>,
        <luto@...nel.org>, "Thomas Gleixner" <tglx@...utronix.de>,
        <bp@...e.de>, <dave.hansen@...ux.intel.com>, <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        <charishma1.gairuboyina@...el.com>,
        <kumar.n.dwarakanath@...el.com>, <ravi.v.shankar@...el.com>
Subject: Re: [PATCH v5 07/12] x86/cpu/keylocker: Load an internal wrapping key
 at boot-time

On 8/23/2022 8:49 AM, Evan Green wrote:
> On Wed, Jan 12, 2022 at 1:21 PM Chang S. Bae <chang.seok.bae@...el.com> wrote:
>>
<snip>
>> +
>> +static void __init load_keylocker(void)
> 
> I am late to this party by 6 months, but:
> load_keylocker() cannot be __init, as it gets called during SMP core onlining.

Yeah, it looks like the case with this patch only.

But the next patch [1] limits the call during boot time only:

	if (c == &boot_cpu_data) {
		...
		load_keylocker();
		...
	} else {
		...
		if (!kl_setup.initialized) {
			load_keylocker();
		} else if (valid_kl) {
			rc = copy_keylocker();
			...
		}
	}

kl_setup.initialized is set by native_smp_cpus_done() -> 
destroy_keylocker_data() when CPUs are booted. Then load_keylocker() is 
not called because the root key (aka IWKey) is no longer available in 
memory.

Now this 'valid_kl' flag should be always on unless the root key backup 
is corrupted. Then copy_keylocker() loads the root key from the backup 
in the platform state.

So I think the onlining CPU won't call it.

Maybe this bit can be much clarified in a separate (new) patch, instead 
of being part of another like [1].

Thanks,
Chang

[1]: 
https://lore.kernel.org/lkml/20220112211258.21115-9-chang.seok.bae@intel.com/