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Re: [kernel-hardening] Re: [RFC, PATCH] x86_64: KAISER - do not map kernel in user mode

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> 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...

> If it helps I can redo the same test also on bare metal.

I'm not sure how we proceed here and if this would help, because I don't 
know what everyone expects.
KAISER definitely introduces an overhead, no doubt about that. How much 
overhead it is depends on the specific hardware and may be very little 
on recent architectures and more on older machines.
We are not proposing to enable KAISER by default, but to provide the 
config option to allow easy integration into hardened kernels where 
performance overheads may be acceptable (which depends on the specific 
use case and the specific hardware).

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[RFC, PATCH] x86_64: KAISER - do not map kernel in user mode Daniel Gruss <daniel.gruss@iaik.tugraz.at> - 2017-05-04 12:20 +0200
  Re: [RFC, PATCH] x86_64: KAISER - do not map kernel in user mode Daniel Gruss <daniel.gruss@iaik.tugraz.at> - 2017-05-04 14:30 +0200
  Re: [kernel-hardening] [RFC, PATCH] x86_64: KAISER - do not map  kernel in user mode Thomas Garnier <thgarnie@google.com> - 2017-05-04 17:30 +0200
    Re: [kernel-hardening] [RFC, PATCH] x86_64: KAISER - do not map  kernel in user mode Daniel Gruss <daniel.gruss@iaik.tugraz.at> - 2017-05-05 10:30 +0200
      Re: [kernel-hardening] [RFC, PATCH] x86_64: KAISER - do not map  kernel in user mode Thomas Garnier <thgarnie@google.com> - 2017-05-05 17:50 +0200
        Re: [kernel-hardening] [RFC, PATCH] x86_64: KAISER - do not map  kernel in user mode David Gens <david.gens@cs.tu-darmstadt.de> - 2017-05-06 06:40 +0200
          Re: [kernel-hardening] [RFC, PATCH] x86_64: KAISER - do not map  kernel in user mode Daniel Gruss <daniel.gruss@iaik.tugraz.at> - 2017-05-06 10:40 +0200
            Re: [kernel-hardening] [RFC, PATCH] x86_64: KAISER - do not map  kernel in user mode Mark Rutland <mark.rutland@arm.com> - 2017-05-08 12:30 +0200
              Re: [kernel-hardening] [RFC, PATCH] x86_64: KAISER - do not map  kernel in user mode Daniel Gruss <daniel.gruss@iaik.tugraz.at> - 2017-05-08 13:00 +0200
                Re: [kernel-hardening] [RFC, PATCH] x86_64: KAISER - do not map  kernel in user mode Mark Rutland <mark.rutland@arm.com> - 2017-05-08 15:30 +0200
                Re: [kernel-hardening] [RFC, PATCH] x86_64: KAISER - do not map  kernel in user mode Daniel Gruss <daniel.gruss@iaik.tugraz.at> - 2017-05-08 15:50 +0200
            Re: [kernel-hardening] [RFC, PATCH] x86_64: KAISER - do not map  kernel in user mode Daniel Gruss <daniel.gruss@iaik.tugraz.at> - 2017-05-08 16:00 +0200
              Re: [kernel-hardening] [RFC, PATCH] x86_64: KAISER - do not map  kernel in user mode Thomas Garnier <thgarnie@google.com> - 2017-05-08 16:20 +0200
                Re: [kernel-hardening] [RFC, PATCH] x86_64: KAISER - do not map  kernel in user mode Daniel Gruss <daniel.gruss@iaik.tugraz.at> - 2017-05-08 16:20 +0200
      Re: [kernel-hardening] [RFC, PATCH] x86_64: KAISER - do not map  kernel in user mode Daniel Gruss <daniel.gruss@iaik.tugraz.at> - 2017-05-08 15:30 +0200
  Re: [RFC, PATCH] x86_64: KAISER - do not map kernel in user mode Christoph Hellwig <hch@infradead.org> - 2017-05-04 17:50 +0200
    Re: [RFC, PATCH] x86_64: KAISER - do not map kernel in user mode Daniel Gruss <daniel.gruss@iaik.tugraz.at> - 2017-05-05 09:50 +0200
      Re: [kernel-hardening] Re: [RFC, PATCH] x86_64: KAISER - do not map  kernel in user mode Daniel Gruss <daniel.gruss@iaik.tugraz.at> - 2017-05-07 23:50 +0200
        Re: [kernel-hardening] Re: [RFC, PATCH] x86_64: KAISER - do not map  kernel in user mode Richard Weinberger <richard@nod.at> - 2017-05-08 00:10 +0200
          Re: [kernel-hardening] Re: [RFC, PATCH] x86_64: KAISER - do not map  kernel in user mode Daniel Gruss <daniel.gruss@iaik.tugraz.at> - 2017-05-08 00:20 +0200
            Re: [kernel-hardening] Re: [RFC, PATCH] x86_64: KAISER - do not mapkernel in user mode "Fogh, Anders" <anders.fogh@gdata-adan.de> - 2017-05-09 17:00 +0200
              Re: [kernel-hardening] Re: [RFC, PATCH] x86_64: KAISER - do not  mapkernel in user mode Richard Weinberger <richard@nod.at> - 2017-05-09 17:00 +0200
                Re: [kernel-hardening] Re: [RFC, PATCH] x86_64: KAISER - do not  mapkernel in user mode Rik van Riel <riel@redhat.com> - 2017-05-09 17:40 +0200
      Re: [kernel-hardening] Re: [RFC, PATCH] x86_64: KAISER - do not map  kernel in user mode Richard Weinberger <richard.weinberger@gmail.com> - 2017-05-08 00:10 +0200
  Re: [kernel-hardening] [RFC, PATCH] x86_64: KAISER - do not map  kernel in user mode Jann Horn <jannh@google.com> - 2017-05-05 18:00 +0200
    Re: [kernel-hardening] [RFC, PATCH] x86_64: KAISER - do not map  kernel in user mode Daniel Gruss <daniel.gruss@iaik.tugraz.at> - 2017-05-06 10:30 +0200
  Re: [kernel-hardening] [RFC, PATCH] x86_64: KAISER - do not map  kernel in user mode Jann Horn <jannh@google.com> - 2017-05-05 18:00 +0200

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