linux-kernel - Re: [PATCH v4 1/3] x86: Introduce a new constant KERNEL_MAPPING

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Date:   Fri, 3 Mar 2017 12:43:49 +0100
From:   Borislav Petkov <bp@...e.de>
To:     Baoquan He <bhe@...hat.com>
Cc:     tglx@...utronix.de, hpa@...or.com, mingo@...hat.com,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        keescook@...omium.org, yinghai@...nel.org, anderson@...hat.com,
        luto@...nel.org, thgarnie@...gle.com, kuleshovmail@...il.com
Subject: Re: [PATCH v4 1/3] x86: Introduce a new constant KERNEL_MAPPING_SIZE

On Sun, Feb 26, 2017 at 12:09:08PM +0800, Baoquan He wrote:
> Am I right on understanding it?

That's exactly what I mean: KERNEL_IMAGE_SIZE is 512M by default but
we're not hard-constrained to it - we're hard-constrained to a 1G limit
as this is the 1G which is covered by level2_kernel_pgt.

And in thinking about this more, I know I suggested making the
KERNEL_IMAGE_SIZE by default 1G in order to simplify things.

But you're adding another KERNEL_MAPPING_SIZE which confuses things
more. And I fail to see why we absolutely need it.

So we suggest kernel image size should be 512M but then we still will
be using a whole 1G mapping for it anyway and a whole page of PMDs at
level2_kernel_pgt.

So why even bother?

Just make it 1G and don't introduce anything new.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--