linux-kernel - Re: [PATCH v4 1/2] x86/setup: always add the beginning of RAM as memblock.memory

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Message-ID: <CAHk-=wjJLdjqN2W_hwUmYCM8u=1tWnKsm46CYfdKPP__anGvJw@mail.gmail.com>
Date:   Sat, 30 Jan 2021 16:37:54 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Baoquan He <bhe@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        David Hildenbrand <david@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Łukasz Majczak <lma@...ihalf.com>,
        Mel Gorman <mgorman@...e.de>, Michal Hocko <mhocko@...nel.org>,
        Mike Rapoport <rppt@...ux.ibm.com>, Qian Cai <cai@....pw>,
        "Sarvela, Tomi P" <tomi.p.sarvela@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vlastimil Babka <vbabka@...e.cz>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>, stable <stable@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: [PATCH v4 1/2] x86/setup: always add the beginning of RAM as memblock.memory

On Sat, Jan 30, 2021 at 2:10 PM Mike Rapoport <rppt@...nel.org> wrote:
>
> In either case, e820__memblock_setup() won't add the range 0x0000 - 0x1000
> to memblock.memory and later during memory map initialization this range is
> left outside any zone.

Honestly, this just sounds like memblock being stupid in the first place.

Why aren't these zones padded to sane alignments?

This patch smells like working around the memblock code being fragile
rather than a real fix.

That's *particularly* true when the very line above it did a
"memblock_reserve()" of the exact same range that the memblock_add()
"adds".

              Linus