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

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Message-ID: <20220419153002.ffh2ybdl7x2mm7zw@box.shutemov.name>
Date:   Tue, 19 Apr 2022 18:30:02 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     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>,
        Dave Hansen <dave.hansen@...el.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 Tue, Apr 19, 2022 at 09:39:53AM +0200, Borislav Petkov wrote:
> On Tue, Apr 19, 2022 at 02:50:15AM +0300, Kirill A. Shutemov wrote:
> > I find it strange that you go after <linux/bitmap.h> which has limited
> > exposure while <linux/acpi.h> and <linux/efi.h> are there already.
> 
> Funny you should mention that:
> 
> https://lore.kernel.org/r/YlCKWhMJEMUgJmjF@zn.tnic
> 
> I *have* been working towards that but it's a losing whack-a-mole game
> when you and others keep adding new stuff.
> 
> So no, we won't take a pile of changes and let the maintainer clean it
> up afterwards.
> 
> > What do you want me to do here?
> 
> 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?

> > // <asm/bitops.h>
> 
> The asm/ stuff can be put into a shared/ namespace header like the io
> stuff you did.
> 
> > As 1 bit represents 2M, not all chunks can be represented in the bitmap
> > and they have to be accepted. But the *goal* is to record unaccepted
> > memory into bitmap. Some accepting is a side effect.
> > 
> > The early_accept_memory() name is just wrong.
> 
> Ok, how about process_unaccepted_memory(). It should be generic enough.

Sounds good.

-- 
 Kirill A. Shutemov