Re: [PATCH RFC 00/10] Intel EPT-Based Sub-page Write Protection Support.

[Paolo Bonzini]

On 16/10/2017 02:08, Yi Zhang wrote:
>> And the introspection facility by Mihai uses a completely
>> different API for the introspector, based on sockets rather than ioctls.
>> So I'm not sure this is the right API at all.
>
> Currently,  We only block the write access, As far as I know an example,
> we now using it in a security daemon:

Understood.  However, I think QEMU is the wrong place to set this up.

If the kernel wants to protect _itself_, it should use a hypercall.  If
an introspector appliance wants to protect the guest kernel, it should
use the socket that connects it to the hypervisor.

Paolo

> Consider It has a server which launching in the host user-space, and a
> client launching in the guest kernel. Yes, they are communicate with
> sockets. The guest kernel wanna protect a special area to prevent all
> the process including the kernel itself modify this area. the client
> could send the guest physical address via the security socket to server
> side, and server would update these protection into KVM. Thus, all the
> write access in a guest specific area will be blocked.
> 
> Now the implementation only on the second half(maybe third ^_^) of this
> example: 'How kvm set the write-protect into a specific GFN?'
> 
> Maybe a user space tools which use ioctl let kvm mmu update the
> write-protection is a better choice.
>