linux-kernel - Re: [PATCH v8 6/7] x86: Add support for ZSTD compressed kernel

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Message-ID: <D5815CBB-EAA8-4942-80CA-874DA325EE7A@fb.com>
Date:   Mon, 27 Jul 2020 22:44:37 +0000
From:   Nick Terrell <terrelln@...com>
To:     Arvind Sankar <nivedita@...m.mit.edu>
CC:     Sedat Dilek <sedat.dilek@...il.com>,
        Nick Terrell <nickrterrell@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "Chris Mason" <clm@...com>,
        "linux-kbuild@...r.kernel.org" <linux-kbuild@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Petr Malat <oss@...at.biz>, Kees Cook <keescook@...omium.org>,
        Kernel Team <Kernel-team@...com>,
        Adam Borowski <kilobyte@...band.pl>,
        Patrick Williams <patrickw3@...com>,
        Michael van der Westhuizen <rmikey@...com>,
        "mingo@...nel.org" <mingo@...nel.org>,
        Patrick Williams <patrick@...cx.xyz>,
        Norbert Lange <nolange79@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alex Xu <alex_y_xu@...oo.ca>
Subject: Re: [PATCH v8 6/7] x86: Add support for ZSTD compressed kernel



> On Jul 24, 2020, at 7:30 AM, Arvind Sankar <nivedita@...m.mit.edu> wrote:
> 
> On Fri, Jul 24, 2020 at 02:50:34AM +0200, Sedat Dilek wrote:
>> On Thu, Jul 23, 2020 at 9:30 PM Nick Terrell <nickrterrell@...il.com> wrote:
>>> 
>>> From: Nick Terrell <terrelln@...com>
>>> 
>>> * Add support for zstd compressed kernel
>>> * Define __DISABLE_EXPORTS in misc.c
>>> * Bump the heap size for zstd.
>>> * Update the documentation.
>>> 
>>> Integrates the ZSTD decompression code to the x86 pre-boot code.
>>> 
>>> Zstandard requires slightly more memory during the kernel decompression
>>> on x86 (192 KB vs 64 KB), and the memory usage is independent of the
>>> window size.
>>> 
>>> __DISABLE_EXPORTS is defined in misc.c instead of the Makefile because
>>> kaslr.c defines __DISABLE_EXPORTS, and defining it in the Makefile gives
>>> duplicate definition warnings.
>>> 
>> 
>> That was reported by Arvind - feel free to add a Reported-by: ...
>> 
>> - Sedat -
>> 
> 
> It's not necessary to add Reported-by's for problems encountered while
> developing the series. Especially as it was my drive-by suggestion to
> use __DISABLE_EXPORTS that introduced the issue in the first place :)
> 
> I'd have added it to the Makefile and just dropped the definition in
> kaslr.c -- should be no reason for anything in here to use EXPORT_SYMBOL.

Sure, I was a bit hesitant to modify more than necessary here, but I will go
ahead and do that.

Thanks for the reviews!