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Date:   Tue, 2 Nov 2021 07:07:34 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Wei Fu <wefu@redhat.com>
Cc:     Christoph Hellwig <hch@infradead.org>,
        Anup Patel <anup.patel@wdc.com>,
        Atish Patra <atish.patra@wdc.com>,
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        Philipp Tomsich <philipp.tomsich@vrull.eu>,
        Christoph Hellwig <hch@lst.de>,
        Liu Shaohua <liush@allwinnertech.com>,
        Wei Wu =?utf-8?B?KOWQtOS8nyk=?= <lazyparser@gmail.com>,
        Drew Fustini <drew@beagleboard.org>,
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        Xinhaoqu <xinhaoqu@huawei.com>,
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Subject: Re: [RESEND PATCH V3 2/2] riscv: add RISC-V Svpbmt extension
 supports
Message-ID: <20211102060734.GB27015@lst.de>
References: <20211025040607.92786-1-wefu@redhat.com> <20211025040607.92786-3-wefu@redhat.com> <YXZU/3/YmRGFrOXK@infradead.org> <CA+YCwKkX64A8p9vfLJHC3+LqOWyDg99eDBR0mjfB=H45BOyJLQ@mail.gmail.com>
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On Mon, Oct 25, 2021 at 06:55:09PM +0800, Wei Fu wrote:
> How about this macro:
> #define _SVPBMT_PMA         0x0UL
> #define _SVPBMT_NC         BIT(61)
> #define _SVPBMT_IO         BIT(62)
> #define _SVPBMT_MASK         GENMASK(62, 61)

Personally I find these macros highly confusing. 

#define _SVPBMT_PMA	0UL
#define _SVPBMT_NC	(1UL << 61)
#define _SVPBMT_IO	(1UL << 62).
#define _SVPBMT_MASK	(_SVPBMT_NC  | _SVPBMT_IO)

is much eaier to follow.  Note that we can probably just drop
_SVPBMT_PMA entirely to make this even more readable.

> > Also why not use the standard names for these _PAGE bits used by
> > most other architectures?
> 
> Which names are you suggesting? Would you mind providing an example ?
> _PAGE_BIT_   for _PAGE_KERNEL_ ??

Use _PAGE_NOCACHE for _SVPBMT_NC, and _PAGE_IO for _SVPBMT_IO.