linux-kernel - Re: [PATCHv6 03/15] efi/x86: Get full memory map in allocate

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Date:   Wed, 1 Jun 2022 11:00:23 +0200
From:   David Hildenbrand <david@...hat.com>
To:     "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>
Cc:     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>,
        Mike Rapoport <rppt@...nel.org>, 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: [PATCHv6 03/15] efi/x86: Get full memory map in allocate_e820()

On 17.05.22 17:34, Kirill A. Shutemov wrote:
> Currently allocate_e820() only interested in the size of map and size of
> memory descriptor to determine how many e820 entries the kernel needs.
> 
> UEFI Specification version 2.9 introduces a new memory type --
> unaccepted memory. To track unaccepted memory kernel needs to allocate
> a bitmap. The size of the bitmap is dependent on the maximum physical
> address present in the system. A full memory map is required to find
> the maximum address.
> 
> Modify allocate_e820() to get a full memory map.

Usually we use max_pfn, if we want to know the maximum pfn that's
present in the system (well, IIRC, excluding hotunplug).

How exactly will this (different?) maximum from UEFI for the bitmap
interact with

max_pfn = e820__end_of_ram_pfn();

from e820 in existing code

?

-- 
Thanks,

David / dhildenb