Re: [PATCH 4/4] x86,module: Detect CRn and DRn manipulation

Paolo Bonzini
2020-04-07T22:12:22Z

On 07/04/20 23:27, Peter Zijlstra wrote:
> On Tue, Apr 07, 2020 at 02:22:11PM -0700, Nadav Amit wrote:
>> Anyhow, I do not think it is the only use-case which is not covered by your
>> patches (even considering CRs/DRs alone). For example, there is no kernel
>> function to turn on CR4.VMXE, which is required to run hypervisors on x86.
> That needs an exported function; there is no way we'll allow random
> writes to CR4, there's too much dodgy stuff in there.

native_write_cr4 and pv_ops (through which you can do write_cr4) are
both exported, and so is cpu_tlbstate which is used by __cr4_set_bits
and friends. Am I missing something glaringly obvious?

Paolo