From: Paolo Bonzini <pbonzini@redhat.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Amit Shah <amit.shah@redhat.com>,
Anthony Liguori <aliguori@us.ibm.com>,
Andreas Faerber <afaerber@suse.de>,
qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH 0/6] add paravirtualization hwrng support
Date: Mon, 29 Oct 2012 09:45:09 +0100 [thread overview]
Message-ID: <508E4215.6050803@redhat.com> (raw)
In-Reply-To: <508AF2C0.30404@zytor.com>
Il 26/10/2012 22:29, H. Peter Anvin ha scritto:
>>> This is surreal. Output from /dev/hwrng turns into output for /dev/random... it us guaranteed worse; period, end of story.
>> >
>> > Isn't that exactly what happens in bare-metal? hwrng -> rngd -> random. Instead here
>> > we'd have, host hwrng -> virtio-rng-pci -> guest hwrng -> guest rngd -> guest random.
>> >
>> > The only difference is that you paravirtualize access to the host hwrng to a) distribute
>> > entropy to multiple guests; b) support migration across hosts with different CPUs and
>> > hardware.
> First, hwrng is only one of the sources used by rngd. It can also
> (currently) use RDRAND or TPM; additional sources are likely to be added
> in the future.
>
> Second, the harvesting of environmental noise -- timings -- is not as
> good in a VM as on plain hardware, so for the no-hwrng case it is better
> for this to be done in the host than in the VM.
Neither of these make /dev/random with virtio-rng-pci worse than without
(as would be the case if you fed /dev/urandom). And migration works.
This, and avoiding denial of service for the host's /dev/random, is all
I care about at this time.
There is always time to change defaults to something better.
Paolo
next prev parent reply other threads:[~2012-10-29 8:45 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-26 14:43 [Qemu-devel] [PATCH 0/6] add paravirtualization hwrng support Anthony Liguori
2012-10-26 14:43 ` [Qemu-devel] [PATCH 1/6] vl: add -object option to create QOM objects from the command line Anthony Liguori
2012-10-26 14:43 ` [Qemu-devel] [PATCH 2/6] object: add object_property_add_bool (v2) Anthony Liguori
2012-10-26 14:43 ` [Qemu-devel] [PATCH 3/6] rng: add RndBackend abstract object class Anthony Liguori
2012-10-26 14:43 ` [Qemu-devel] [PATCH 4/6] rng-random: add an RNG backend that uses /dev/random Anthony Liguori
2012-10-26 14:43 ` [Qemu-devel] [PATCH 5/6] rng-egd: introduce EGD compliant RNG backend Anthony Liguori
2012-10-26 14:43 ` [Qemu-devel] [PATCH 6/6] virtio-rng: hardware random number generator device Anthony Liguori
2012-10-26 15:08 ` [Qemu-devel] [PATCH 0/6] add paravirtualization hwrng support Paolo Bonzini
2012-10-26 15:42 ` Anthony Liguori
2012-10-26 16:09 ` H. Peter Anvin
2012-10-26 18:24 ` Anthony Liguori
2012-10-26 18:26 ` H. Peter Anvin
2012-10-29 6:23 ` Amit Shah
2012-10-30 4:32 ` H. Peter Anvin
2012-10-26 18:58 ` Paolo Bonzini
2012-10-26 19:07 ` H. Peter Anvin
2012-10-26 19:51 ` Paolo Bonzini
2012-10-26 19:54 ` H. Peter Anvin
2012-10-26 20:29 ` H. Peter Anvin
2012-10-29 8:45 ` Paolo Bonzini [this message]
2012-10-30 4:34 ` H. Peter Anvin
2012-10-30 4:43 ` H. Peter Anvin
2012-10-30 9:05 ` Paolo Bonzini
2012-10-30 21:11 ` H. Peter Anvin
2012-10-31 7:29 ` Paolo Bonzini
2012-10-31 14:15 ` H. Peter Anvin
2012-10-31 14:27 ` Paolo Bonzini
2012-10-26 18:53 ` Paolo Bonzini
2012-10-29 7:01 ` Amit Shah
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