linux-kernel - Re: [PATCHv3 2/7] efi/x86: Get full memory map in allocate

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Message-ID: <20220131234437.twazkxvsdukhq2xs@box.shutemov.name>
Date:   Tue, 1 Feb 2022 02:44:37 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Dave Hansen <dave.hansen@...el.com>
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>,
        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: [PATCHv3 2/7] efi/x86: Get full memory map in allocate_e820()

On Mon, Jan 31, 2022 at 02:38:42PM -0800, Dave Hansen wrote:
> On 1/28/22 12:59, Kirill A. Shutemov wrote:
> > Modify allocate_e820() to get a full memory map.
> 
> Dumb question time: why doesn't the current code get a full memory map?
>  This looks simpler.  What's the downside?  Memory consumption?

Yeah, it requires memory allocation that has to be freed back.

Otherwise I don't see any downsides. There are several more EFI calls, but
it should not make a noticable difference on boot time.

-- 
 Kirill A. Shutemov