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Date:   Mon, 27 Apr 2020 01:10:29 +0800
From:   Jiaxun Yang <jiaxun.yang@flygoat.com>
To:     Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Guoyun Sun <sunguoyun@loongson.cn>
CC:     Paul Burton <paulburton@kernel.org>,
        Daniel Silsby <dansilsby@gmail.com>,
        Paul Cercueil <paul@crapouillou.net>,
        Dmitry Korotin <dkorotin@wavecomp.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Steven Price <steven.price@arm.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Anshuman Khandual <anshuman.khandual@arm.com>,
        linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org,
        TieZhu Yang <yangtiezhu@loongson.cn>,
        Xuefeng Li <lixuefeng@loongson.cn>
Subject: Re: [PATCH] mips/mm: Add page soft dirty tracking
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=E4=BA=8E 2020=E5=B9=B44=E6=9C=8827=E6=97=A5 GMT+08:00 =E4=B8=8A=E5=8D=881=
2:54:42, Thomas Bogendoerfer <tsbogend@alpha=2Efranken=2Ede> =E5=86=99=E5=
=88=B0:
>On Tue, Apr 21, 2020 at 05:15:27PM +0800, Guoyun Sun wrote:
>> User space checkpoint and restart tool (CRIU) needs the page's change
>> to be soft tracked=2E This allows to do a pre checkpoint and then dump
>> only touched pages=2E
>>=20
>> Signed-off-by: Guoyun Sun <sunguoyun@loongson=2Ecn>
>> ---
>>  arch/mips/Kconfig                    |  1 +
>>  arch/mips/include/asm/pgtable-bits=2Eh |  8 ++++--
>>  arch/mips/include/asm/pgtable=2Eh      | 48 ++++++++++++++++++++++++++=
++++++++--
>
>this breaks all 32bit builds where CPU support RIXI, because it overflows
>pgtable_bits=2E

Probably make a fixup patch to guard
_PAGE_SOFT_DIRTY_SHIFT with
CONFIG_HAVE_ARCH_SOFT_DIRTY
would be a better option?

Btw: It's really selfish that only enable SOFT_DIRTY for Loongson
but occupied a bit in pagetable for all MIPS systems=2E

I'd suggest select HAVE_ARCH_SOFT_DIRTY for all 64BIT MIPS systems=2E
Or provide config options to let expert users decide what feature they nee=
d=2E

Thanks=2E

>
>Thomas=2E
>

--=20
Jiaxun Yang