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 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
-- strict thread matches above, loose matches on Subject: below --
2014-04-28 19:52 [PATCH] random: Add "initialized" variable to proc Florian Weimer
2014-04-28 21:41 ` Theodore Ts'o
2014-04-29 17:51 ` Florian Weimer
2014-04-29 18:26 ` Theodore Ts'o
2014-04-30 20:52 ` Andy Lutomirski
2014-05-01 2:06 ` Theodore Ts'o
2014-05-01 4:05 ` H. Peter Anvin
2014-05-01 15:05 ` tytso
2014-05-01 15:35 ` Andy Lutomirski
2014-05-01 18:53 ` Andy Lutomirski
2014-05-01 18:59 ` random: Providing a seed value to VM guests H. Peter Anvin
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