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

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Date:   Sat, 13 Oct 2018 16:19:59 -0400
From:   Masayoshi Mizuma <msys.mizuma@...il.com>
To:     Chao Fan <fanc.fnst@...fujitsu.com>, Baoquan He <bhe@...hat.com>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     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

Baoquan and Chao, thank you for your comments!

Boris, the patches has been merged to linux-next.
Should I create a new patch for linux-next?
I'm trying to make the padding size set automatically.

Thanks,
Masa

On Thu, Oct 11, 2018 at 01:51:54PM +0800, Chao Fan wrote:
> On Thu, Oct 11, 2018 at 08:29:55AM +0800, Baoquan He wrote:
> >On 10/10/18 at 03:44pm, Masayoshi Mizuma wrote:
> >> On Wed, Oct 10, 2018 at 05:30:57PM +0800, Baoquan He wrote:
> >> > On 10/10/18 at 11:19am, Borislav Petkov wrote:
> >> > > On Wed, Oct 10, 2018 at 11:14:26AM +0200, Thomas Gleixner wrote:
> >> > > > Yes, it's different, but if the SRAT information is available early, then
> >> > > > the command line parameter can go away because then the required
> >> > > > information for Masa's problem is available as well.
> >> > > 
> >> > > Exactly. And I'd prefer we delayed the command line parameter until we
> >> > > figure out we really need it and not expose it to upstream and then
> >> > > remove it shortly after.
> >> > > 
> >> > > So I'd suggest we move Masa's patches to a separate branch and not send
> >> > > it up this round.
> >> > 
> >> > Yes, sounds more reasonable if we can reuse functions in Chao's patch 1/3
> >> > to solve the padding issue.
> >> 
> >> Thanks for your comments! Yes, immovable_mem[num_immovable_mem] in Chao's
> >> patch may be useful for calculating the padding size. If so, we don't
> >> need the new kernel parameter. It's nice!
> >> 
> >> Do you happen to have ideas how we access immovable_mem[num_immovable_mem]
> >> from arch/x86/mm/kaslr.c ? It is located to arch/x86/boot/compressed/*, so
> >> I suppose it is not easy to access it... 
> >> I would appreciate if you could give some advice.
> >
> >Hmm, they are living in different life cycle and space. So we can only
> >reuse the code from Chao's patch, but not the variable. Means we need
> >go through the SRAT accessing again in arch/x86/mm/kaslr.c and fill
> >immovable_mem[num_immovable_mem] for mm/kaslr.c usage, if we decide to
> >do like that.
> 
> Reading three times is redundant, but reading two times is needed.
> Becasue the ACPI code run very stable, but we need more information
> before that.
> As for Masa's issue, I am wondering whether we can tranfer the
> information or only the address of SRAT table from compressed period
> to the period after start_kernel().
> 
> Thanks,
> Chao Fan
> 
> >
> >Thanks
> >Baoquan
> >
> >
> 
>