linux-kernel - Re: [kernel-hardening] Re: [RFC, PATCH] x86_64: KAISER

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Date:   Sun, 7 May 2017 22:20:31 +0200
From:   Richard Weinberger <richard.weinberger@...il.com>
To:     Daniel Gruss <daniel.gruss@...k.tugraz.at>
Cc:     Christoph Hellwig <hch@...radead.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        "clementine.maurice@...k.tugraz.at" 
        <clementine.maurice@...k.tugraz.at>,
        "moritz.lipp@...k.tugraz.at" <moritz.lipp@...k.tugraz.at>,
        Michael Schwarz <michael.schwarz@...k.tugraz.at>,
        Richard Fellner <richard.fellner@...dent.tugraz.at>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ingo Molnar <mingo@...nel.org>,
        "anders.fogh@...ta-adan.de" <anders.fogh@...ta-adan.de>
Subject: Re: [kernel-hardening] Re: [RFC, PATCH] x86_64: KAISER - do not map
 kernel in user mode

Daniel,

On Fri, May 5, 2017 at 9:40 AM, Daniel Gruss
<daniel.gruss@...k.tugraz.at> wrote:
> I'm sure the overhead on older systems is larger than on recent systems.

Just did a quick test on my main KVM host, a 8 core Intel(R) Xeon(R)
CPU E3-1240 V2.
KVM guests are 4.10 w/o CONFIG_KAISER and kvmconfig without CONFIG_PARAVIRT.
Building a defconfig kernel within that guests is about 10% slower
when CONFIG_KAISER
is enabled.

Is this expected?
If it helps I can redo the same test also on bare metal.

-- 
Thanks,
//richard