From: tytso@mit.edu
To: Andy Lutomirski <luto@amacapital.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
Florian Weimer <fweimer@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Kees Cook <kees@outflux.net>, kvm list <kvm@vger.kernel.org>
Subject: Re: random: Providing a seed value to VM guests
Date: Thu, 1 May 2014 19:26:18 +0000 [thread overview]
Message-ID: <20140501192618.GA25829@thunk.org> (raw)
In-Reply-To: <CALCETrXMAWSC6B-irn4LeXFzB2tODqagsBboky=xnGv5ZTh-sg@mail.gmail.com>
On Thu, May 01, 2014 at 12:02:49PM -0700, Andy Lutomirski wrote:
>
> Is RDSEED really reasonable here? Won't it slow down by several
> orders of magnitude?
That is I think the biggest problem; RDRAND and RDSEED are fast if
they are native, but they will involve a VM exit if they need to be
emulated. So when an OS might want to use RDRAND and RDSEED might be
quite different if we know they are being emulated.
Using the RDRAND and RDSEED "api" certainly makes sense, at least for
x86, but I suspect we might want to use a different way of signalling
that a VM guest can use RDRAND and RDSEED if they are running on a CPU
which doesn't provide that kind of access. Maybe a CPUID extended
function parameter, if one could be allocated for use by a Linux
hypervisor?
- Ted
next prev parent reply other threads:[~2014-05-01 19:26 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-01 19:02 random: Providing a seed value to VM guests Andy Lutomirski
2014-05-01 19:26 ` tytso [this message]
2014-05-01 19:40 ` H. Peter Anvin
2014-05-01 20:16 ` Andy Lutomirski
2014-05-01 20:30 ` H. Peter Anvin
2014-05-01 20:32 ` Andy Lutomirski
2014-05-01 20:39 ` tytso
2014-05-01 20:56 ` Andy Lutomirski
2014-05-01 21:01 ` H. Peter Anvin
2014-05-01 21:06 ` Andy Lutomirski
2014-05-01 22:28 ` tytso
2014-05-01 22:32 ` Andy Lutomirski
2014-05-01 22:46 ` H. Peter Anvin
2014-05-01 22:56 ` Andy Lutomirski
2014-05-01 23:00 ` H. Peter Anvin
2014-05-01 19:41 ` H. Peter Anvin
[not found] <20140428195913.E0A0143994596@oldenburg.str.redhat.com>
[not found] ` <20140428214112.GC7857@thunk.org>
[not found] ` <535FE68C.8060002@redhat.com>
[not found] ` <20140429182610.GA19325@thunk.org>
[not found] ` <53616293.3080308@mit.edu>
[not found] ` <20140501020627.GA25248@thunk.org>
[not found] ` <1be5350d-89f9-44b9-8d1b-e3e591741940@email.android.com>
[not found] ` <20140501150549.GA24388@thunk.org>
[not found] ` <CALCETrUQRqKEbWps5Nxqk57vCYmuvcA6pYAL7OiqJy8sE8yh=g@mail.gmail.com>
2014-05-01 18:53 ` [PATCH] random: Add "initialized" variable to proc Andy Lutomirski
2014-05-01 18:59 ` random: Providing a seed value to VM guests H. Peter Anvin
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