linux-kernel - Re: Arm64 crash while reading memory sysfs

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Date:   Wed, 26 May 2021 14:04:26 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     "Qian Cai (QUIC)" <quic_qiancai@...cinc.com>
Cc:     Mike Rapoport <rppt@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: Arm64 crash while reading memory sysfs

On Wed, May 26, 2021 at 12:09:14PM +0000, Qian Cai (QUIC) wrote:
> [    0.000000] Early memory node ranges
> [    0.000000]   node   0: [mem 0x0000000090000000-0x0000000091ffffff]

Maybe de-selecting HOLES_IN_ZONE is not correct for arm64 in all
circumstances. In a configuration with 64K pages, MAX_ORDER is 14,
MAX_ORDER_NR_PAGES is 8192, so a 2^29 address range. However, the above
range starts on 2^28 boundary.

SECTION_SIZE_BITS is 29 in this configuration but the corresponding
mem_map[] in the first half of the first section is probably not marked
as reserved as we'd do for NOMAP.

-- 
Catalin