Re: [PATCH 3/3] KVM: PPC: Book3S: Add support for hwrng found on some powernv systems

Gleb Natapov
2013-10-02T14:37:37Z

On Wed, Oct 02, 2013 at 04:33:18PM +0200, Paolo Bonzini wrote:
> Il 02/10/2013 16:08, Alexander Graf ha scritto:
> > > The hwrng is accessible by host userspace via /dev/mem.
> >
> > A guest should live on the same permission level as a user space
> > application. If you run QEMU as UID 1000 without access to /dev/mem, why
> > should the guest suddenly be able to directly access a memory location
> > (MMIO) it couldn't access directly through a normal user space interface.
> >
> > It's basically a layering violation.
>
> With Michael's earlier patch in this series, the hwrng is accessible by
> host userspace via /dev/hwrng, no?
>
Access to which can be controlled by its permission. Permission of
/dev/kvm may be different. If we route hypercall via userspace and
configure qemu to get entropy from /dev/hwrng everything will fall
nicely together (except performance).

--
Gleb.