Re: [PATCH v2 0/4] Enable SMEP CPU Feature

From: Avi Kivity
Date: Tue May 17 2011 - 05:32:56 EST

On 05/17/2011 12:29 PM, Ingo Molnar wrote:
* Avi Kivity<avi@xxxxxxxxxx> wrote:

> > Some programmable configurability seems necessary on the KVM side, as KVM
> > has no control over how sane the guest kernel is.
> We should simply expose the cpuid bit and cr4.smep. If the guest kernel
> feels it is up to it, it can enable smep itself.

Well, given that there's lots of legacy installations around it would be a neat
KVM feature if it was possible to enable SMEP even if the guest kernel does not
enable it. As an additional (optional) layer of security.

For example legacy Linux guests will work just fine, even if they do not enable
SMEP themselves.

It's certainly possible (set CR4.SMEP transparently and hide it from the guest). But there's no way to tell if it doesn't break something wierd. The host might not even know if the guest is Linux or something else.

We could support it as a non-default feature, but that reduces its utility.

error compiling committee.c: too many arguments to function

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