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 barel
On Thu, May 1, 2014 at 3:46 PM, H. Peter Anvin wrote:
> On 05/01/2014 03:32 PM, Andy Lutomirski wrote:
>> On Thu, May 1, 2014 at 3:28 PM, wrote:
>>> On Thu, May 01, 2014 at 02:06:13PM -0700, Andy Lutomirski wrote:
I still don't see the point. What does this do better than virtio-rng?
On 05/01/2014 03:32 PM, Andy Lutomirski wrote:
> On Thu, May 1, 2014 at 3:28 PM, wrote:
>> On Thu, May 01, 2014 at 02:06:13PM -0700, Andy Lutomirski wrote:
>>>
>>> I still don't see the point. What does this do better than virtio-rng?
>>
>> I believe you had been complaining about how complicate
On Thu, May 1, 2014 at 3:28 PM, wrote:
> On Thu, May 01, 2014 at 02:06:13PM -0700, Andy Lutomirski wrote:
>>
>> I still don't see the point. What does this do better than virtio-rng?
>
> I believe you had been complaining about how complicated it was to set
> up virtio? And this complexity is a
On Thu, May 01, 2014 at 02:06:13PM -0700, Andy Lutomirski wrote:
>
> I still don't see the point. What does this do better than virtio-rng?
I believe you had been complaining about how complicated it was to set
up virtio? And this complexity is also an issue if we want to use it
to initialize t
On Thu, May 1, 2014 at 2:01 PM, H. Peter Anvin wrote:
> On 05/01/2014 01:56 PM, Andy Lutomirski wrote:
>>
>> Even if we could emulate RDSEED effectively**, I don't really
>> understand what the guest is expected to do with it. And I generally
>> dislike defining an interface with no known sensibl
On 05/01/2014 01:56 PM, Andy Lutomirski wrote:
>
> Even if we could emulate RDSEED effectively**, I don't really
> understand what the guest is expected to do with it. And I generally
> dislike defining an interface with no known sensible users, because it
> means that there's a good chance that
On Thu, May 1, 2014 at 1:39 PM, wrote:
> On Thu, May 01, 2014 at 01:32:55PM -0700, Andy Lutomirski wrote:
>> On Thu, May 1, 2014 at 1:30 PM, H. Peter Anvin wrote:
>> > RDSEED is not synchronous. It is, however, nonblocking.
>>
>> What I mean is: IIUC it's reasonable to call RDSEED a few times i
On Thu, May 01, 2014 at 01:32:55PM -0700, Andy Lutomirski wrote:
> On Thu, May 1, 2014 at 1:30 PM, H. Peter Anvin wrote:
> > RDSEED is not synchronous. It is, however, nonblocking.
>
> What I mean is: IIUC it's reasonable to call RDSEED a few times in a
> loop and hope it works. It makes no sen
On Thu, May 1, 2014 at 1:30 PM, H. Peter Anvin wrote:
> RDSEED is not synchronous. It is, however, nonblocking.
What I mean is: IIUC it's reasonable to call RDSEED a few times in a
loop and hope it works. It makes no sense to do that with
/dev/random.
>
> On May 1, 2014 1:16:40 PM PDT, Andy Lu
RDSEED is not synchronous. It is, however, nonblocking.
On May 1, 2014 1:16:40 PM PDT, Andy Lutomirski wrote:
>On May 1, 2014 12:26 PM, wrote:
>>
>> 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
>> > o
On May 1, 2014 12:26 PM, wrote:
>
> 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
The normal CPUID bit is unset I believe.
On May 1, 2014 12:02:49 PM PDT, Andy Lutomirski wrote:
>On Thu, May 1, 2014 at 11:59 AM, H. Peter Anvin wrote:
>> On 05/01/2014 11:53 AM, Andy Lutomirski wrote:
>>>
>>> A CPUID leaf or an MSR advertised by a CPUID leaf has another
>>> advantage: it's easy
As I said... I think KVM has already added an emulated instructions enumeration
API.
On May 1, 2014 12:26:18 PM PDT, ty...@mit.edu wrote:
>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 magnitud
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
emula
On Thu, May 1, 2014 at 11:59 AM, H. Peter Anvin wrote:
> On 05/01/2014 11:53 AM, Andy Lutomirski wrote:
>>
>> A CPUID leaf or an MSR advertised by a CPUID leaf has another
>> advantage: it's easy to use in the ASLR code -- I don't think there's
>> a real IDT, so there's nothing like rdmsr_safe ava
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