linux-kernel - Re: [PATCHv4 3/8] efi/x86: Implement support for unaccepted memory

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Date:   Tue, 19 Apr 2022 09:38:53 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>,
        Borislav Petkov <bp@...en8.de>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        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>,
        Peter Zijlstra <peterz@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Varad Gautam <varad.gautam@...e.com>,
        Dario Faggioli <dfaggioli@...e.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Mike Rapoport <rppt@...nel.org>,
        David Hildenbrand <david@...hat.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: [PATCHv4 3/8] efi/x86: Implement support for unaccepted memory

On 4/19/22 08:30, Kirill A. Shutemov wrote:
>> I think the stuff coming from the linux/ namespace you can simply copy
>> into a header in compressed/, like I've done with efi.h.
> Hm. Dave was worried about having copies of _find_next_bit() and
> __bitmap_*() inside compressed/.
> 
> How do we rectify code duplication and making decompresser self-contained?
> Do we care about multiple copies of the same code in the kernel?
> Do we care about keeping them in sync?

Would it be feasible to have the common code defined as a 'static
inline' in a header that both the main kernel and the decompressor could
include?  Something like the attached patch.

I'd much rather duplicate something like this:

int strncasecmp(const char *s1, const char *s2, size_t len)
{
        return __lib_strncasecmp(s1, s1, len);
}

in the decompressor versus a real full implementation.
View attachment "lib-header.patch" of type "text/x-patch" (1770 bytes)