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Subject: Re: [kernel-hardening] Re: [RFC, PATCH] x86_64: KAISER - do not map
 kernel in user mode
To: Daniel Gruss <daniel.gruss@iaik.tugraz.at>
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From: Richard Weinberger <richard@nod.at>
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Date: Mon, 8 May 2017 00:02:41 +0200
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Daniel,

Am 07.05.2017 um 23:45 schrieb Daniel Gruss:
>> 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.
> 
> Thank you for testing it! :)
> 
>> Is this expected?
> 
> It sounds plausible. First, I would expect any form of virtualization to increase the overhead. Second, for the processor (Ivy Bridge), I would have expected even higher
> performance overheads. KAISER utilizes very recent performance improvements in Intel processors...

Ahh, *very* recent is the keyword then. ;)
I was a bit confused since in your paper the overhead is less than 1%.

What platforms did you test?
i.e. how does it perform on recent AMD systems?

Thanks,
//richard