linux-kernel - Re: [patch 5/9] x86/ioport: Reduce ioperm impact for sane usage further

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Date:   Thu, 7 Nov 2019 08:53:25 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Willy Tarreau <w@....eu>, Peter Anvin <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Juergen Gross <jgross@...e.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [patch 5/9] x86/ioport: Reduce ioperm impact for sane usage further

On Thu, Nov 7, 2019 at 8:45 AM Eric W. Biederman <ebiederm@...ssion.com> wrote:
>
> Further a quick look shows that dosemu uses ioperm in a fine grained
> manner.  From memory it would allow a handful of ports to allow directly
> accessing a device and depended on the rest of the port accesses to be
> disallowed so it could trap and emulate them.

Yes. Making ioperm() some all-or-nothing thing would be horribly bad,
and has no real advantages that I can see.

               Linus