linux-kernel - Re: [PATCH v2 0/3] Create 'old' ptes for faultaround mappings on arm64 with hardware access flag

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Message-ID: <20210111142402.6euyktmcnpemanf7@box>
Date:   Mon, 11 Jan 2021 17:24:02 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Will Deacon <will@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Jan Kara <jack@...e.cz>, Minchan Kim <minchan@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Vinayak Menon <vinmenon@...eaurora.org>,
        Hugh Dickins <hughd@...gle.com>,
        Android Kernel Team <kernel-team@...roid.com>
Subject: Re: [PATCH v2 0/3] Create 'old' ptes for faultaround mappings on
 arm64 with hardware access flag

On Fri, Jan 08, 2021 at 11:34:08AM -0800, Linus Torvalds wrote:
> I still dislike how we basically randomly modify the information in
> that 'vmf' thing.

I wounder if it would be acceptable to pass down to faultaround a copy
of vmf, so it mess with it without risking to corrupt the original one?

We would need to transfer back prealloc_pte, but the rest can be safely
discarded, I believe.

But it's somewhat wasteful of stack. sizeof(vmf) == 96 on x86-64.

-- 
 Kirill A. Shutemov