linux-kernel - Re: [RFC V1 09/31] arm/mm: Enable ARCH_HAS_VM_GET_PAGE

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Message-ID: <3bab7cde-f394-3e51-57a1-32be271762ae@arm.com>
Date:   Tue, 25 Jan 2022 09:06:46 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        hch@...radead.org, akpm@...ux-foundation.org,
        Arnd Bergmann <arnd@...db.de>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC V1 09/31] arm/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT



On 1/24/22 10:36 PM, Russell King (Oracle) wrote:
> On Mon, Jan 24, 2022 at 06:26:46PM +0530, Anshuman Khandual wrote:
>> This defines and exports a platform specific custom vm_get_page_prot() via
>> subscribing ARCH_HAS_VM_GET_PAGE_PROT. Subsequently all __SXXX and __PXXX
>> macros can be dropped which are no longer needed.
>
> What is the fundamental advantage of this approach?
> 

Remove multiple 'core MM <--> platform' abstraction layers to map
vm_flags access permission combination into page protection. From
the cover letter ..

----------
Currently there are multiple layers of abstraction i.e __SXXX/__PXXX macros
, protection_map[], arch_vm_get_page_prot() and arch_filter_pgprot() built
between the platform and generic MM, finally defining vm_get_page_prot().

Hence this series proposes to drop all these abstraction levels and instead
just move the responsibility of defining vm_get_page_prot() to the platform
itself making it clean and simple.
----------