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Date:   Thu, 7 Nov 2019 11:13:57 +0100
From:   Willy Tarreau <w@1wt.eu>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     Ingo Molnar <mingo@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        Stephen Hemminger <stephen@networkplumber.org>,
        Juergen Gross <jgross@suse.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [patch 5/9] x86/ioport: Reduce ioperm impact for sane usage
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On Thu, Nov 07, 2019 at 11:00:27AM +0100, Thomas Gleixner wrote:
> Changing ioperm(single port, port range) to be ioperm(all) is going to
> break a bunch of test cases which actually check whether the permission is
> restricted to a single I/O port or the requested port range.

But out of curiosity, are these solely test cases or things that real
applications do ? We could imagine having a sysctl entry to indicate
whether or not we want strict compatibility with older code in which
case we'd take the slow path, or a modernized behavior using only the
fast path. If we managed to deal with mmap_min_addr over time, I think
it should be manageable to deal with the rare applications using ioperm().

Willy