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SubjectRe: [PATCH 2/4] KVM: x86: Introduce paravirt feature CR0/CR4 pinning
On 7/9/20 9:07 AM, Andy Lutomirski wrote:
> On Thu, Jul 9, 2020 at 8:56 AM Dave Hansen <> wrote:
>> On 7/9/20 8:44 AM, Andersen, John wrote:
>>> Bits which are allowed to be pinned default to WP for CR0 and SMEP,
>>> SMAP, and UMIP for CR4.
>> I think it also makes sense to have FSGSBASE in this set.
>> I know it hasn't been tested, but I think we should do the legwork to
>> test it. If not in this set, can we agree that it's a logical next step?
> I have no objection to pinning FSGSBASE, but is there a clear
> description of the threat model that this whole series is meant to
> address? The idea is to provide a degree of protection against an
> attacker who is able to convince a guest kernel to write something
> inappropriate to CR4, right? How realistic is this?

If a quick search can find this:


I'd pretty confident that the guys doing actual bad things have it in
their toolbox too.

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