linux-kernel - Re: [PATCH v8 0/3] x86/boot/KASLR: Parse ACPI table and limit kaslr in immovable memory

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Message-ID: <20181106193636.svyjwuwrlgnpuyyf@gabell>
Date:   Tue, 6 Nov 2018 14:36:38 -0500
From:   Masayoshi Mizuma <msys.mizuma@...il.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Baoquan He <bhe@...hat.com>, Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Chao Fan <fanc.fnst@...fujitsu.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-efi@...r.kernel.org, linux-acpi@...r.kernel.org,
        mingo@...hat.com, hpa@...or.com, keescook@...omium.org,
        rjw@...ysocki.net, lenb@...nel.org, ard.biesheuvel@...aro.org,
        indou.takao@...fujitsu.com, caoj.fnst@...fujitsu.com
Subject: Re: [PATCH v8 0/3] x86/boot/KASLR: Parse ACPI table and limit kaslr
 in immovable memory

On Tue, Nov 06, 2018 at 07:45:19PM +0100, Borislav Petkov wrote:
> Ok, having swapped the whole thing back into my brain, forget what I
> said earlier today.
> 
> Didn't we talk about passing info with setup_data to the later kernel
> stage? You even had a patch:
> 
> https://lkml.kernel.org/r/20181022154204.kagmdb55jtoez4ca@gabell
> 
> So what is that "idea" again about adding SRAT parsing code to
> arch/x86/mm/kaslr.c?!?!
> 
> The intent of passing info with setup_data is to *avoid* parsing SRAT
> yet another time and duplicating that code one more time.
> 
> IOW:
> 
> * The first place that needs SRAT parsing, does the parsing - i.e., the
> compressed stage.
> 
> * Later stages get information passed to them with setup_data. No second
> parsing.
> 
> Ok?

Yes, I think I can see what you are saying. However, I'm not sure how
I use the setup_data in legacy BIOS environment. So, I said the another
idea which adding the SRAT parsing code to arch/x86/mm/kaslr.c as well.
Yes, as you said, that is not so good...

I would appreciate if you could help to use setup_data or something to
pass the information to later kernel stage in BIOS environment.

Thanks,
Masa