[PATCH 3/3] KVM: PPC: Book3S: Add support for hwrng found on some powernv systems
michael at ellerman.id.au
Tue Oct 1 18:34:26 EST 2013
On Thu, Sep 26, 2013 at 11:06:59AM +0200, Paolo Bonzini wrote:
> Il 26/09/2013 08:31, Michael Ellerman ha scritto:
> > Some powernv systems include a hwrng. Guests can access it via the
> > H_RANDOM hcall.
> Is there any reason to do this in the kernel?
It's less code, and it's faster :)
> It does not have to be a particularly fast path;
Sure, but do we have to make it slow on purpose?
> on x86, we are simply forwarding /dev/hwrng or
> /dev/random data to the guest. You can simply use virtio-rng.
Not all guests support virtio-rng.
> If you really want to have the hypercall, implementing it in QEMU means
> that you can support it on all systems, in fact even when running
> without KVM.
Sure, I can add a fallback to /dev/hwrng for full emulation.
> The QEMU command line would be something like "-object
> rng-random,filename=/dev/random,id=rng0 -device spapr-rng,rng=rng0".
We can't use /dev/random like that. The PAPR specification, which is
what we're implementing, implies that H_RANDOM provides data from a
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