linux-kernel - Re: [PATCH] x86/vm86/32: Remove VM86_SCREEN

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Date:   Fri, 8 Jan 2021 18:39:43 -0500
From:   Andrea Arcangeli <aarcange@...hat.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     x86@...nel.org, LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>, Jason Gunthorpe <jgg@...pe.ca>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Jann Horn <jannh@...gle.com>, Jan Kara <jack@...e.cz>,
        Yu Zhao <yuzhao@...gle.com>, Peter Xu <peterx@...hat.com>
Subject: Re: [PATCH] x86/vm86/32: Remove VM86_SCREEN_BITMAP support

On Fri, Jan 08, 2021 at 10:55:05AM -0800, Andy Lutomirski wrote:
> The implementation was rather buggy.  It unconditionally marked PTEs
> released the mmap lock before flushing the TLB, which could allow a racing
> CoW operation to falsely believe that the underlying memory was not
> writable.
> 
> I can't find any users at all of this mechanism, so just remove it.

Reviewed-by: Andrea Arcangeli <aarcange@...hat.com>