linux-kernel - Re: [patch V2 10/16] x86/ioperm: Remove bitmap if all permissions dropped

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Date:   Tue, 12 Nov 2019 09:43:11 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Linus Torvalds <torvalds@...uxfoundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Willy Tarreau <w@....eu>, Juergen Gross <jgross@...e.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [patch V2 10/16] x86/ioperm: Remove bitmap if all permissions dropped

On Mon, Nov 11, 2019 at 2:35 PM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> If ioperm() results in a bitmap with all bits set (no permissions to any
> I/O port), then handling that bitmap on context switch and exit to user
> mode is pointless. Drop it.
>
> Move the bitmap exit handling to the ioport code and reuse it for both the
> thread exit path and dropping it. This allows to reuse this code for the
> upcoming iopl() emulation.

Acked-by: Andy Lutomirski <luto@...nel.org>