linux-kernel - Re: [PATCH v3 02/11] x86/ldt: Simplify LDT switching logic

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Date:   Wed, 21 Jun 2017 10:03:14 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andy Lutomirski <luto@...nel.org>
cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Nadav Amit <nadav.amit@...il.com>,
        Rik van Riel <riel@...hat.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v3 02/11] x86/ldt: Simplify LDT switching logic

On Tue, 20 Jun 2017, Andy Lutomirski wrote:
> When we redo lazy mode to stop flush IPIs without switching to
> init_mm, though, the current logic would become incorrect: it will
> be possible to have real_prev == next but nonetheless have a stale
> LDT descriptor.
> 
> Simplify the code to update LDTR if either the previous or the next
> mm has an LDT, i.e. effectively restore the historical logic..
> While we're at it, clean up the code by moving all the ifdeffery to
> a header where it belongs.
> 
> Acked-by: Rik van Riel <riel@...hat.com>
> Signed-off-by: Andy Lutomirski <luto@...nel.org>

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>