linux-kernel - Re: [PATCHv7 05/14] x86/boot: Add infrastructure required for unaccepted memory support

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Date:   Wed, 15 Jun 2022 18:05:34 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Joerg Roedel <jroedel@...e.de>,
        Ard Biesheuvel <ardb@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Tom Lendacky <thomas.lendacky@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Varad Gautam <varad.gautam@...e.com>,
        Dario Faggioli <dfaggioli@...e.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Mike Rapoport <rppt@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        marcelo.cerri@...onical.com, tim.gardner@...onical.com,
        khalid.elmously@...onical.com, philip.cox@...onical.com,
        x86@...nel.org, linux-mm@...ck.org, linux-coco@...ts.linux.dev,
        linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv7 05/14] x86/boot: Add infrastructure required for
 unaccepted memory support

On Wed, Jun 15, 2022 at 12:19:45PM +0200, Peter Zijlstra wrote:
> On Tue, Jun 14, 2022 at 03:02:22PM +0300, Kirill A. Shutemov wrote:
> > Pull functionality from the main kernel headers and lib/ that is
> > required for unaccepted memory support.
> > 
> > This is preparatory patch. The users for the functionality will come in
> > following patches.
> > 
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> > ---
> >  arch/x86/boot/bitops.h                   | 40 ++++++++++++
> >  arch/x86/boot/compressed/align.h         | 14 +++++
> >  arch/x86/boot/compressed/bitmap.c        | 43 +++++++++++++
> >  arch/x86/boot/compressed/bitmap.h        | 49 +++++++++++++++
> >  arch/x86/boot/compressed/bits.h          | 36 +++++++++++
> >  arch/x86/boot/compressed/compiler.h      |  9 +++
> >  arch/x86/boot/compressed/find.c          | 54 ++++++++++++++++
> >  arch/x86/boot/compressed/find.h          | 80 ++++++++++++++++++++++++
> >  arch/x86/boot/compressed/math.h          | 37 +++++++++++
> >  arch/x86/boot/compressed/minmax.h        | 61 ++++++++++++++++++
> >  arch/x86/boot/compressed/pgtable_types.h | 25 ++++++++
> 
> That's quite a lot of duplicated code; is there really no way so share
> this?

Code duplication also make me uncomfortable. But that what Borislav wanted
to see. efi.h in the boot stub which copies bulk of <linux/efi.h> also
sets the trend in the direction.

Alternative is creating a subset of headers that can be used in both in
main kernel and boot stub. It is more complex and doesn't allow for short
cuts that can be made on copy if you know the context it is used in.

It also sounds painfully similar to uapi/ project. I'm not sure we want to
go this path.

-- 
 Kirill A. Shutemov