linux-kernel - Re: [PATCH] mips/mm: Add page soft dirty tracking

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Date:   Mon, 27 Apr 2020 01:10:29 +0800
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Guoyun Sun <sunguoyun@...ngson.cn>
CC:     Paul Burton <paulburton@...nel.org>,
        Daniel Silsby <dansilsby@...il.com>,
        Paul Cercueil <paul@...pouillou.net>,
        Dmitry Korotin <dkorotin@...ecomp.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Steven Price <steven.price@....com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        TieZhu Yang <yangtiezhu@...ngson.cn>,
        Xuefeng Li <lixuefeng@...ngson.cn>
Subject: Re: [PATCH] mips/mm: Add page soft dirty tracking



于 2020年4月27日 GMT+08:00 上午12:54:42, Thomas Bogendoerfer <tsbogend@...ha.franken.de> 写到:
>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. This allows to do a pre checkpoint and then dump
>> only touched pages.
>> 
>> Signed-off-by: Guoyun Sun <sunguoyun@...ngson.cn>
>> ---
>>  arch/mips/Kconfig                    |  1 +
>>  arch/mips/include/asm/pgtable-bits.h |  8 ++++--
>>  arch/mips/include/asm/pgtable.h      | 48 ++++++++++++++++++++++++++++++++++--
>
>this breaks all 32bit builds where CPU support RIXI, because it overflows
>pgtable_bits.

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.

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

Thanks.

>
>Thomas.
>

-- 
Jiaxun Yang