linux-kernel - Re: [PATCH v2 2/2] x86/sev: Add callback to apply RMP table fixups for kexec.

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Date: Fri, 26 Apr 2024 09:56:25 -0500
From: "Kalra, Ashish" <ashish.kalra@....com>
To: Borislav Petkov <bp@...en8.de>
Cc: thomas.lendacky@....com, michael.roth@....com, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] x86/sev: Add callback to apply RMP table fixups
 for kexec.

On 4/26/2024 7:58 AM, Borislav Petkov wrote:

> On Wed, Apr 24, 2024 at 06:48:08PM -0500, Kalra, Ashish wrote:
>> This callback needs to be invoked as part of setup_arch() as it needs e820
>> table to be setup in e820__memory_setup() before the callback is invoked and
>> snp_init() is called from sme_enable() in kernel/head_64.S (startup_64),
>> which is much before start_kernel() -> setup_arch() is invoked.
> So?
>
> snp_init() still runs before e820__memory_setup(). So what's stopping
> you?

As i have already explained above, snp_init() runs before 
e820__memory_setup() so we can't invoke this callback in snp_init() as 
e820 tables have still not been setup. Again to summarize, the e820 
tables are setup in e820__memory_setup() which runs after snp_init().

Additionally, RMP table also get probed after snp_init(). So this 
callback cannot be invoked in snp_init().

I have added this comment to v3 of this patch series which i posted 
yesterday, so please look at those.

Thanks, Ashish