linux-kernel - Re: [PATCH v4 6/8] x86: bump ZO_z_extra

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Date:   Fri, 3 Apr 2020 12:19:29 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Nick Terrell <terrelln@...com>
Cc:     Nick Terrell <nickrterrell@...il.com>,
        "linux-kernel@...r.kernel.org" <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>,
        Sedat Dilek <sedat.dilek@...il.com>
Subject: Re: [PATCH v4 6/8] x86: bump ZO_z_extra_bytes margin for zstd

On Thu, Apr 02, 2020 at 08:25:49PM +0000, Nick Terrell wrote:
> So it is possible that there is a use case for kernel compression that
> I’m not aware of where RAM is extremely tight and within 64 KB of
> the current limits.

That's exactly my concern, albeit a very minor one.

> It seems to me that adding 64KB to the memory requirement for kernel
> decompression is not going to break anyone. If it did the kernel image
> is taking up nearly all available RAM, which doesn’t seem likely.
> But, I don’t know all use cases. If it does break someone, we can
> put up a separate patch that switches all the compression methods over
> a per-method ZO_z_extra_bytes.

Ok.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette