Re: random: Providing a seed value to VM guests

[H. Peter Anvin]

As I said... I think KVM has already added an emulated instructions enumeration API.

On May 1, 2014 12:26:18 PM PDT, tytso@xxxxxxx 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 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

-- 
Sent from my mobile phone.  Please pardon brevity and lack of formatting.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/