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

Il 02/10/2013 16:36, Alexander Graf ha scritto:

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With Michael's earlier patch in this series, the hwrng is accessible by
host userspace via /dev/hwrng, no?

Yes, but there's not token from user space that gets passed into the
kernel to check whether access is ok or not. So while QEMU may not have
permission to open /dev/hwrng it could spawn a guest that opens it,
drains all entropy out of it and thus stall other processes which try to
fetch entropy, no?

Maybe I haven't fully grasped the interface yet though :).

Yes, that's right.  I don't think it's a huge problem, but it's another
point in favor of just doing the hypercall in userspace.

Paolo