From: "H. Peter Anvin" <hpa@zytor.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: "Theodore Ts'o" <tytso@mit.edu>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
kvm list <kvm@vger.kernel.org>,
Florian Weimer <fweimer@redhat.com>, Kees Cook <kees@outflux.net>
Subject: Re: random: Providing a seed value to VM guests
Date: Thu, 01 May 2014 16:00:31 -0700 [thread overview]
Message-ID: <5362D20F.6010401@zytor.com> (raw)
In-Reply-To: <CALCETrUqOb6EnyWq15Q-1CXec53rDorR2Ka+nF--iugMUzWCOA@mail.gmail.com>
On 05/01/2014 03:56 PM, Andy Lutomirski wrote:
>
> I think we're comparing:
>
> a) cpuid to detect rdrand *or* emulated rdrand followed by rdrand
>
> to
>
> b) cpuid to detect rdrand or the paravirt seed msr/cpuid call,
> followed by rdrand or the msr or cpuid read
>
> this seems like it barely makes a difference, especially since (a)
> probably requires detecting KVM anyway.
Well, it lets one do something like:
if (boot_cpu_has(X86_FEATURE_RDRAND) ||
boot_cpu_has(X86_FEATURE_RDRAND_SIMULATED))
rdrand_long(...);
We need the ifs anyway for early code; the arch_*() interfaces are only
available after alternatives run.
-hpa
next prev parent reply other threads:[~2014-05-01 23:00 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
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 [this message]
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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