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Re: [PATCH v2 2/3] x86 Test and expose CPUID faulting capabilities in /proc/cpuinfo

From Andy Lutomirski <luto@amacapital.net>
Newsgroups linux.kernel
Subject Re: [PATCH v2 2/3] x86 Test and expose CPUID faulting capabilities in /proc/cpuinfo
Date 2016-09-15 03:20 +0200
Message-ID <shtvj-dX-1@gated-at.bofh.it> (permalink)
References <shpBn-665-13@gated-at.bofh.it> <shpBn-665-11@gated-at.bofh.it> <shq4p-6gS-7@gated-at.bofh.it> <shqxs-6H5-21@gated-at.bofh.it>
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On Wed, Sep 14, 2016 at 3:03 PM, Kyle Huey <me@kylehuey.com> wrote:
> On Wed, Sep 14, 2016 at 2:35 PM, Dave Hansen
> <dave.hansen@linux.intel.com> wrote:
>> On 09/14/2016 02:01 PM, Kyle Huey wrote:

>> Is any of this useful to optimize away at compile-time?  We have config
>> options for when we're running as a guest, and this seems like a feature
>> that isn't available when running on bare metal.
>
> On the contrary, this is only available when we're on bare metal.
> Neither Xen nor KVM virtualize CPUID faulting (although KVM correctly
> suppresses MSR_PLATFORM_INFO's report of support for it).

KVM could easily support this.  If rr starts using it, I think KVM
*should* add support, possibly even for older CPUs that don't support
the feature in hardware.

It's too bad that x86 doesn't give us the instruction bytes on a
fault.  Otherwise we could lazily switch this feature.

--Andy

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Thread

[PATCH v2 2/3] x86 Test and expose CPUID faulting capabilities in /proc/cpuinfo Kyle Huey <me@kylehuey.com> - 2016-09-14 23:10 +0200
  Re: [PATCH v2 2/3] x86 Test and expose CPUID faulting capabilities in  /proc/cpuinfo Dave Hansen <dave.hansen@linux.intel.com> - 2016-09-14 23:40 +0200
    Re: [PATCH v2 2/3] x86 Test and expose CPUID faulting capabilities in /proc/cpuinfo Kyle Huey <me@kylehuey.com> - 2016-09-15 00:10 +0200
      Re: [PATCH v2 2/3] x86 Test and expose CPUID faulting capabilities in /proc/cpuinfo Andy Lutomirski <luto@amacapital.net> - 2016-09-15 03:20 +0200
        Re: [PATCH v2 2/3] x86 Test and expose CPUID faulting capabilities in /proc/cpuinfo Kyle Huey <me@kylehuey.com> - 2016-09-15 04:30 +0200
        Re: [PATCH v2 2/3] x86 Test and expose CPUID faulting capabilities in /proc/cpuinfo "H. Peter Anvin" <hpa@zytor.com> - 2016-09-15 22:50 +0200
          Re: [PATCH v2 2/3] x86 Test and expose CPUID faulting capabilities in /proc/cpuinfo Andy Lutomirski <luto@amacapital.net> - 2016-09-16 01:20 +0200
    Re: [PATCH v2 2/3] x86 Test and expose CPUID faulting capabilities in  /proc/cpuinfo David Vrabel <david.vrabel@citrix.com> - 2016-09-15 12:10 +0200
  Re: [Xen-devel] [PATCH v2 2/3] x86 Test and expose CPUID faulting  capabilities in /proc/cpuinfo David Vrabel <david.vrabel@citrix.com> - 2016-09-15 12:10 +0200
    Re: [Xen-devel] [PATCH v2 2/3] x86 Test and expose CPUID  faulting capabilities in /proc/cpuinfo "Jan Beulich" <JBeulich@suse.com> - 2016-09-15 12:30 +0200
      Re: [Xen-devel] [PATCH v2 2/3] x86 Test and expose CPUID faulting  capabilities in /proc/cpuinfo Kyle Huey <me@kylehuey.com> - 2016-09-15 21:20 +0200
        Re: [Xen-devel] [PATCH v2 2/3] x86 Test and expose CPUID faulting  capabilities in /proc/cpuinfo Andy Lutomirski <luto@amacapital.net> - 2016-09-15 21:40 +0200
          Re: [Xen-devel] [PATCH v2 2/3] x86 Test and expose CPUID faulting  capabilities in /proc/cpuinfo Kyle Huey <me@kylehuey.com> - 2016-09-16 01:40 +0200
        Re: [Xen-devel] [PATCH v2 2/3] x86 Test and expose CPUID faulting  capabilities in /proc/cpuinfo Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-09-15 21:50 +0200

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