From: Paolo Bonzini <pbonzini@redhat.com>
To: Michael Ellerman <michael@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>, Alexander Graf <agraf@suse.de>,
qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH] spapr: Add support for hwrng when available
Date: Fri, 27 Sep 2013 10:58:40 +0200 [thread overview]
Message-ID: <524548C0.6070602@redhat.com> (raw)
In-Reply-To: <1380270997.20440.6.camel@concordia>
Il 27/09/2013 10:36, Michael Ellerman ha scritto:
> So have the host kernel read from the hwrng, export it to userspace via
> a char device, which is then read by qemu, which then copies it back
> into the host kernel, which can then give it to the guest.
>
> Or from the guest perspective, instead of a cheap switch to host real
> mode and back - a full switch to kernel virtual, then to user, back to
> kernel, back to user, back to kernel, back to guest.
>
> Frankly I can't see why that is a superior option?
Because this is not a fast path at all. Doing things in QEMU lets
people test and configure the paravirtualized hwrng even if they do not
have a hwrng in the host, and even if they are running with emulation
(TCG) instead of KVM.
But as I mentioned in the kernel thread, perhaps you do not need the
hypercall at all if virtio-rng is enough (it should be for Linux guests).
Paolo
prev parent reply other threads:[~2013-09-27 8:58 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-26 6:37 [Qemu-devel] [PATCH] spapr: Add support for hwrng when available Michael Ellerman
2013-09-26 11:06 ` Alexander Graf
2013-09-27 8:36 ` Michael Ellerman
2013-09-27 8:58 ` Paolo Bonzini [this message]
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