linux-kernel - Re: [PATCHv10 04/11] efi/x86: Implement support for unaccepted memory

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Message-ID: <20230509005634.qtuiodpirexbxu2k@box.shutemov.name>
Date:   Tue, 9 May 2023 03:56:34 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Joerg Roedel <jroedel@...e.de>,
        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>,
        Dario Faggioli <dfaggioli@...e.com>,
        Mike Rapoport <rppt@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        marcelo.cerri@...onical.com, tim.gardner@...onical.com,
        khalid.elmously@...onical.com, philip.cox@...onical.com,
        aarcange@...hat.com, peterx@...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: [PATCHv10 04/11] efi/x86: Implement support for unaccepted memory

On Tue, May 09, 2023 at 12:11:41AM +0200, Ard Biesheuvel wrote:
> > @@ -1324,13 +1325,15 @@ void __init e820__memblock_setup(void)
> >          * e820_table is not finalized and e820__end_of_ram_pfn() cannot be
> >          * used to get correct RAM size.
> >          */
> > -       if (boot_params.unaccepted_memory) {
> > +       if (efi.unaccepted != EFI_INVALID_TABLE_ADDR) {
> > +               struct efi_unaccepted_memory *unaccepted;
> >                 unsigned long size;
> >
> > -               /* One bit per 2MB */
> > -               size = DIV_ROUND_UP(e820__end_of_ram_pfn() * PAGE_SIZE,
> > -                                   PMD_SIZE * BITS_PER_BYTE);
> > -               memblock_reserve(boot_params.unaccepted_memory, size);
> > +               unaccepted = __va(efi.unaccepted);
> > +
> > +               size = sizeof(struct efi_unaccepted_memory);
> > +               size += unaccepted->size;
> > +               memblock_reserve(efi.unaccepted, size);
> >         }
> >
> 
> This could be moved to generic code (but we'll need to use early_memremap())

I don't understand why early_memremap() is needed. EFI_LOADER_DATA already
mapped into direct mapping. We only need to reserve the memory so it
could not be reallocated for other things. Hm?

-- 
  Kiryl Shutsemau / Kirill A. Shutemov