From mboxrd@z Thu Jan  1 00:00:00 1970
From: Benjamin Herrenschmidt <benh@au1.ibm.com>
Date: Wed, 02 Oct 2013 21:58:32 +0000
Subject: Re: [PATCH 3/3] KVM: PPC: Book3S: Add support for hwrng found on some powernv systems
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To: Alexander Graf <agraf@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>, Paul Mackerras <paulus@samba.org>, Gleb Natapov <gleb@redhat.com>, Michael Ellerman <michael@ellerman.id.au>, linux-kernel@vger.kernel.org, mpm@selenic.com, herbert@gondor.hengli.com.au, linuxppc-dev@ozlabs.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, tytso@mit.edu

On Wed, 2013-10-02 at 11:11 +0200, Alexander Graf wrote:

> Right, and the difference for the patch in question is really whether
> we handle in in kernel virtual mode or in QEMU, so the bulk of the
> overhead (kicking threads out of  guest context, switching MMU
> context, etc) happens either way.
> 
> So the additional overhead when handling it in QEMU here really boils
> down to the user space roundtrip (plus another random number read
> roundtrip).

Hrm, Michael had a real mode version ... not sure where it went then.

Cheers,
Ben.