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Re: CVE-2017-5754 - XEN silent_disable?

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On Fri, Jan 12, 2018 at 08:08:17PM -0500, bw wrote:
> 
> 
> On Fri, 12 Jan 2018, Vincent Lefevre wrote:
> 
> > But I think I've found the reason:
> > 
> > In arch/x86/mm/kaiser.c:
> > 
> > void __init kaiser_check_boottime_disable(void)
> > {
> > [...]
> >         if (boot_cpu_has(X86_FEATURE_XENPV))
> >                 goto silent_disable;
> > [...]
> > disable:
> >         pr_info("disabled\n");
> > 
> > silent_disable:
> >         kaiser_enabled = 0;
> >         setup_clear_cpu_cap(X86_FEATURE_KAISER);
> > }
> > 
> > I must be in the "silent_disable" case (this is a Xen guest).
> > 
> > It's unfortunate that no-one mentions this case!
> > 
> 
> It is an unfortunate situation all around, no doubt!  I did a quick 
> websearch and found contrary opinions about whether Xen paravirtualization 
> is affected or not, whether a patched server and a patched guest is 
> necessary, and to what degree patching one or the other protects either, 
> and from whom.

FWIW, this is the patch which brought it about:

  http://lists-archives.com/linux-kernel/29009008-kaiser-disabled-on-xen-pv.html

I'm not very happy with the "silent" part either.

Cheers
- -- t
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CVE-2017-5754 - ETA? francis picabia <fpicabia@gmail.com> - 2018-01-04 15:00 +0100
  Re: CVE-2017-5754 - ETA? Don Armstrong <don@debian.org> - 2018-01-04 21:50 +0100
    Re: CVE-2017-5754 - ETA? francis picabia <fpicabia@gmail.com> - 2018-01-08 16:40 +0100
      Re: CVE-2017-5754 - ETA? Jeroen Mathon <jeroenmathonmac@gmail.com> - 2018-01-08 17:20 +0100
      Re: CVE-2017-5754 - ETA? Tixy <tixy@yxit.co.uk> - 2018-01-08 18:10 +0100
        Re: CVE-2017-5754 - ETA? Sven Joachim <svenjoac@gmx.de> - 2018-01-08 18:40 +0100
      Re: CVE-2017-5754 - ETA? Richard Hector <richard@walnut.gen.nz> - 2018-01-08 22:30 +0100
        Re: CVE-2017-5754 - ETA? francis picabia <fpicabia@gmail.com> - 2018-01-10 13:50 +0100
    Re: CVE-2017-5754 - ETA? Vincent Lefevre <vincent@vinc17.net> - 2018-01-12 14:40 +0100
      Re: CVE-2017-5754 - ETA? bw <bwtnguy@yahoo.com> - 2018-01-12 16:10 +0100
        Re: CVE-2017-5754 - ETA? Jack Dangler <tdldev@gmail.com> - 2018-01-12 17:00 +0100
          Re: CVE-2017-5754 - ETA? Roberto C. Sánchez <roberto@debian.org> - 2018-01-12 17:00 +0100
        Re: CVE-2017-5754 - ETA? Vincent Lefevre <vincent@vinc17.net> - 2018-01-12 22:10 +0100
          Re: CVE-2017-5754 - ETA? Roberto C. Sánchez <roberto@debian.org> - 2018-01-12 22:20 +0100
            Re: CVE-2017-5754 - ETA? Vincent Lefevre <vincent@vinc17.net> - 2018-01-12 22:20 +0100
          Re: CVE-2017-5754 - ETA? Nick <debuser@acrasis.net> - 2018-01-12 22:30 +0100
            Re: CVE-2017-5754 - ETA? Vincent Lefevre <vincent@vinc17.net> - 2018-01-12 22:50 +0100
              Re: CVE-2017-5754 - XEN silent_disable? bw <bwtnguy@yahoo.com> - 2018-01-13 02:10 +0100
                Re: CVE-2017-5754 - XEN silent_disable? <tomas@tuxteam.de> - 2018-01-13 08:30 +0100
                Re: CVE-2017-5754 - XEN silent_disable? Vincent Lefevre <vincent@vinc17.net> - 2018-01-13 10:50 +0100
                Re: CVE-2017-5754 - XEN silent_disable? <tomas@tuxteam.de> - 2018-01-13 12:30 +0100
              Re: CVE-2017-5754 - ETA? Tixy <tixy@yxit.co.uk> - 2018-01-13 09:10 +0100
                Re: CVE-2017-5754 - ETA? Tixy <tixy@yxit.co.uk> - 2018-01-13 09:50 +0100

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