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Subject: Re: [PATCH v11 7/7] KVM: x86: virtualize cpuid faulting
From: Nadav Amit <nadav.amit@gmail.com>
In-Reply-To: <20161110234055.8654-8-khuey@kylehuey.com>
Date: Fri, 11 Nov 2016 12:54:46 -0800
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To: Kyle Huey <me@kylehuey.com>
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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