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Re: [PATCH v11 7/7] KVM: x86: virtualize cpuid faulting

From	Nadav Amit <nadav.amit@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v11 7/7] KVM: x86: virtualize cpuid faulting
Date	2016-11-11 22:20 +0100
Message-ID	<sCroS-1fb-29@gated-at.bofh.it> (permalink)
References	<sC7gu-4O8-3@gated-at.bofh.it> <sC7gu-4O8-13@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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> On Nov 10, 2016, at 3:40 PM, Kyle Huey <me@kylehuey.com> wrote:
> 
> Hardware support for faulting on the cpuid instruction is not required to
> emulate it, because cpuid triggers a VM exit anyways. KVM handles the relevant
> MSRs (MSR_PLATFORM_INFO and MSR_MISC_FEATURES_ENABLE) and upon a
> cpuid-induced VM exit checks the cpuid faulting state and the CPL.
> kvm_require_cpl is even kind enough to inject the GP fault for us.

I think that for consistency you should also revise em_cpuid() of KVM
instruction emulator. Otherwise it may be a potential security
hazard (as far fetched as it currently seems).

Nadav

Thread

[PATCH v11 0/7] x86/arch_prctl Add ARCH_[GET|SET]_CPUID for controlling the CPUID instruction Kyle Huey <me@kylehuey.com> - 2016-11-11 00:50 +0100
  [PATCH v11 6/7] x86/arch_prctl: Add ARCH_[GET|SET]_CPUID Kyle Huey <me@kylehuey.com> - 2016-11-11 00:50 +0100
    Re: [PATCH v11 6/7] x86/arch_prctl: Add ARCH_[GET|SET]_CPUID kbuild test robot <lkp@intel.com> - 2016-11-11 02:30 +0100
      Re: [PATCH v11 6/7] x86/arch_prctl: Add ARCH_[GET|SET]_CPUID Kyle Huey <me@kylehuey.com> - 2016-11-11 02:40 +0100
  [PATCH v11 3/7] x86/arch_prctl: Add do_arch_prctl_common Kyle Huey <me@kylehuey.com> - 2016-11-11 00:50 +0100
  [PATCH v11 7/7] KVM: x86: virtualize cpuid faulting Kyle Huey <me@kylehuey.com> - 2016-11-11 00:50 +0100
    Re: [PATCH v11 7/7] KVM: x86: virtualize cpuid faulting Nadav Amit <nadav.amit@gmail.com> - 2016-11-11 22:20 +0100
      Re: [PATCH v11 7/7] KVM: x86: virtualize cpuid faulting Kyle Huey <me@kylehuey.com> - 2016-11-16 17:50 +0100
        Re: [PATCH v11 7/7] KVM: x86: virtualize cpuid faulting Paolo Bonzini <pbonzini@redhat.com> - 2016-11-16 21:50 +0100
          Re: [PATCH v11 7/7] KVM: x86: virtualize cpuid faulting Kyle Huey <me@kylehuey.com> - 2016-11-17 03:00 +0100
  [PATCH v11 1/7] x86/arch_prctl/64: Use SYSCALL_DEFINE2 to define sys_arch_prctl Kyle Huey <me@kylehuey.com> - 2016-11-11 00:50 +0100

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