linux-kernel - Re: [PATCH 2/2] x86/kpti: Reference all cpu_entry

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Message-ID: <alpine.DEB.2.20.1712021136290.2199@nanos>
Date:   Sat, 2 Dec 2017 11:38:09 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andy Lutomirski <luto@...nel.org>
cc:     X86 ML <x86@...nel.org>, Borislav Petkov <bpetkov@...e.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Brian Gerst <brgerst@...il.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH 2/2] x86/kpti: Reference all cpu_entry_area pagetables
 in the usermode tables

On Fri, 1 Dec 2017, Andy Lutomirski wrote:

> We were manually configuring cpu_entry_area in the usermode tables.
> This was error-prone and wasted memory.  (Not much memory, but
> still.)  Instead, just reference the same pagetables.
> 
> This avoids needing to keep the KPTI code and the normal
> cpu_entry_area code in sync, since the KPTI code no longer cares
> what's in cpu_entry_area.
> 
> [This does *not* work on the current KPTI series.  It requires that
>  all the kernelmode cpu_entry_tables are pre-allocated.  That
>  happens in the series as I submitted it, but tglx changed it for
>  reasons that I haven't figured out.]

As I said it crashed and burned for yet unknown reasons. I'll dig into
that.
 
Thanks,

	tglx