Re: [PATCH v2] x86/vm86/32: Remove VM86_SCREEN_BITMAP support

[stsp]

19.01.2021 20:40, Andy Lutomirski пишет:
> The implementation was rather buggy.  It unconditionally marked PTEs
> read-only, even for VM_SHARED mappings.  I'm not sure whether this is
> actually a problem, but it certainly seems unwise.  More importantly, it
> 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.
>
> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> Cc: Linux-MM <linux-mm@xxxxxxxxx>
> Cc: Jason Gunthorpe <jgg@xxxxxxxx>
> Cc: x86@xxxxxxxxxx
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> Cc: Jann Horn <jannh@xxxxxxxxxx>
> Cc: Jan Kara <jack@xxxxxxx>
> Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
> Cc: Peter Xu <peterx@xxxxxxxxxx>
> Cc: Stas Sergeev <stsp@xxxxxxx>
> Cc: Brian Gerst <brgerst@xxxxxxxxx>
> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
> ---
Acked-by: stsp2@xxxxxxxxx

dosemu2 just uses mprotect().
The BIOSSEG stuff in vm86_32.c is also
unused btw.