From: Michael Ellerman <michael@ellerman.id.au>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: tytso@mit.edu, herbert@gondor.apana.org.au, gleb@redhat.com,
linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org,
agraf@suse.de, linuxppc-dev@ozlabs.org,
Paul Mackerras <paulus@samba.org>,
kvm@vger.kernel.org, mpm@selenic.com
Subject: Re: [PATCH 3/3] KVM: PPC: Book3S: Add support for hwrng found on some powernv systems
Date: Tue, 1 Oct 2013 18:34:26 +1000 [thread overview]
Message-ID: <20131001083426.GB27484@concordia> (raw)
In-Reply-To: <5243F933.7000907@redhat.com>
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
hardware source.
cheers
next prev parent reply other threads:[~2013-10-01 8:34 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-26 6:31 [PATCH 1/3] powerpc: Implement arch_get_random_long/int() for powernv Michael Ellerman
2013-09-26 6:31 ` [PATCH 2/3] hwrng: Add a driver for the hwrng found in power7+ systems Michael Ellerman
2013-09-26 8:01 ` Benjamin Herrenschmidt
2013-10-01 8:25 ` Michael Ellerman
2013-09-26 6:31 ` [PATCH 3/3] KVM: PPC: Book3S: Add support for hwrng found on some powernv systems Michael Ellerman
2013-09-26 9:06 ` Paolo Bonzini
2013-10-01 8:34 ` Michael Ellerman [this message]
2013-10-01 8:39 ` Gleb Natapov
2013-10-01 9:23 ` Paul Mackerras
2013-10-01 9:57 ` Gleb Natapov
2013-10-01 10:00 ` Alexander Graf
2013-10-01 9:38 ` Benjamin Herrenschmidt
2013-10-01 11:19 ` Paolo Bonzini
2013-10-01 21:44 ` Benjamin Herrenschmidt
2013-10-02 8:38 ` Paolo Bonzini
2013-10-02 5:09 ` Paul Mackerras
2013-10-02 8:46 ` Paolo Bonzini
2013-10-02 9:06 ` Benjamin Herrenschmidt
2013-10-02 9:11 ` Alexander Graf
2013-10-02 9:50 ` Alexander Graf
2013-10-02 10:02 ` Gleb Natapov
2013-10-02 13:57 ` Michael Ellerman
2013-10-02 14:08 ` Alexander Graf
2013-10-02 14:33 ` Paolo Bonzini
2013-10-02 14:36 ` Alexander Graf
2013-10-02 14:38 ` Paolo Bonzini
2013-10-02 22:45 ` Paul Mackerras
2013-10-03 5:48 ` Gleb Natapov
2013-10-03 10:06 ` Paul Mackerras
2013-10-03 12:08 ` Gleb Natapov
2013-10-02 14:37 ` Gleb Natapov
2013-10-02 22:21 ` Benjamin Herrenschmidt
2013-10-03 6:08 ` Gleb Natapov
2013-10-02 22:13 ` Benjamin Herrenschmidt
2013-10-02 14:10 ` Gleb Natapov
2013-10-02 22:15 ` Benjamin Herrenschmidt
2013-10-02 22:02 ` Benjamin Herrenschmidt
2013-10-03 5:43 ` Gleb Natapov
2013-10-03 7:22 ` Benjamin Herrenschmidt
2013-10-02 22:07 ` Benjamin Herrenschmidt
2013-10-03 6:28 ` Gleb Natapov
2013-10-02 21:58 ` Benjamin Herrenschmidt
2013-10-01 9:58 ` Paolo Bonzini
2013-09-27 14:15 ` Anshuman Khandual
2013-10-01 8:36 ` Michael Ellerman
2013-09-26 7:58 ` [PATCH 1/3] powerpc: Implement arch_get_random_long/int() for powernv Benjamin Herrenschmidt
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